Friday, December 21, 2007

Desktop Tower Defence - not so great after all

After some scientific research, the whole game is reduced into a spread sheet. There are not enough randomness to sustain the game. Only the spawn creeps have some randomness in the way they spawn into several smaller creeps. Also the creeps are dumb. Once you figure out a good way to kill the creeps, they are all dead sooner or later. The mazes don't make a lot of difference when at the end it's all about fire power.

Most weapons are smoke screens on the hard mode for example. You have little choice on a few of the useful weapons.

After I killed all the creeps with ease, I researched how the highest scores are achieved. I think they are smoke screens too. The scores with videos to back up aren't that high. I think many high scores in the scoreboard are categorized by mistake or deliberately. I looked at the associated mazes. Though mazes don't tell you the full story because it's a snapshot of the final moment, but some mazes contain too much money in it for the hard mode. Maybe the money is possible at the very end, but then it's unrelated to how to pass the most difficult stages.

After so long, I should think the highest score gurus would have come out to explain how they invented the winning strategy and earn the bragging right. Perhaps they want to keep it a secret because the game is so simple. Once they tell you everybody know how to beat it with ease, unlike every other console games. Perhaps the scoreboard is really one big smoke screen to keep people playing.

The challenge mode and fun mode are giveaways. The game itself doesn't have that much variation. By using totally different rules, you are playing different games when the original game is done and dead.

Killing all creeps gives you about 7,000 points. If you send the creeps earlier you earn more points. These extra points are about linear, more or less the same at every level. So to get some of the high scores, almost you have to send all creeps at once, which isn't possible. I estimated the max scores possible is about 10,000. I don't know how some 14,000 can be achieved in the hard mode.

So this is my final take on the game, unless some guru come out and explain how they earn high scores. And it have to be interesting, that is, related to real war strategy.

Swarm tower: it's much more efficient for air defense than squirt towers. It had to be at the dead center of the desktop. When you have two, put the 2nd one next to the dead center. The upgrade sequence is simple. When you are at level 7xN, your tower should be SW N. But you don't need any swarm for the first flying creeps when N=1. This assumes that you have a strong enough squirt tower to help with air defense, not busy with other creeps.

For level 7x7, you need two equivalent sw6 towers, such as one sw6 touching two bo5 (50% boost) towers. For level 7x8, flying bosses, you need the equivalent of four sw6 towers, such as two sw6 touching four bo5 towers. Also for the flying bosses you need two frost towers, fr6, to cover both boss.

There could be variations that I didn't exhaust. If you only slow down only one boss, each boss in theory absorb twice the fire power. I did tried with one fr6 to slow down one boss. It worked pretty good but not very consistent. If you need two fr6 to slow down one boss, it doesn't save you $250. You can have five bo5 (maximum boost towers) touching one sw6. It's not too good but it works better with an extra sw5 touching four bo5. I didn't exhaust all these, but the money saved doesn't seem to be that great, so you don't gain a lot of fire power for the other creeps.

You need only one bash tower, the priority of upgrade. It kills all creeps all at once passing through, the strategy to have high scores by sending the next wave of creeps early. But you cannot have bash alone because they cannot kill any boss for their short range. The best "maze" for bash is the cross but degenerates into one square block, and you try to surround the bash so creeps have to run along it on all four sides. See DNA defense in earlier post. But this conflicts with boost towers, which has to touch the bash.

The compromise for the bash maze is for the tower to touch two (or even three) boost towers. There are still three sides for the creeps to run along. This still look somewhat like the DNA defense.

You need only one squirt tower. You need a long range weapon to kill the bosses, and certainly the spawns. It's sufficient if this tower is boosted by two (or three) boost towers. The best maze is a cross three square in width initially, and five square in width at the end. You force the creeps to run around your cross. Your cross have to be small to survive the initial attacks with little money, and enlarging your cross is easy and cheap to do, but very effective. You should integrate one corner or one side of the cross with the bash maze.

You upgrade your squirt along with the bash. You need a spread sheet to be optimum. But simply put, you upgrade when you have money, bash first, until you bay $290 for the squirt before $260 for the bash. And it doesn't matter that much if you are good.

So you have one bash, one squirt, and one swarm. When they are all upgraded to the full, you try to touch them as much as possible with 4 or even more boost towers. When you get to the flying bosses, you need in addition one sw6 touching 4 bo5, and two fr6 covering each flight path.

You also need the so called juggling to send the creeps back and forth at some point. With my sufficient fire power, you can keep juggling to a minimum. Juggling means you don't have good design and enough fire power. The creeps will accumulate and divert fire power if you juggle too much.

For the last two bosses, you must send them out together, so no remaining creeps are to be released. All maze blocks part of the creep's entrance so they are forced into the heart of the maze. When no more creeps are released, you can just unblock the entrance, and block the exit of the maze, so the creeps have to go all the way back to where they started. For a good design they will be killed before they reach the entrance. There are no extra maze needed for juggling.

The only other case you need juggling is for the spawns, especially for the bosses at level 48. But since the next creeps are flying with no more creeps coming out for a long time, you can do the same as the final bosses. But if the spawns aren't killed soon enough, the squirts will be diverting fire power from the flying creeps. Anyway, a little juggling can save you a lot of money for other things. In practice, you need to add a little extra maze such as the DNA pattern to slow down the creeps at the entrance and exit, to give you enough response time to sell and buy blocks.

One possible variation, if boosting the frost towers further slow down the creeps, it would be very useful. But I doubt it, the game isn't that complicated, such as that the boost towers don't boost each other. And if the slow down can be boosted, the game would be too easy.

Friday, November 30, 2007

Triple Cross Defense

After managing to kill everything at the Desktop Tower Defense, I was trying to be scientific to get higher scores. I used the Flying Boss at the easy and normal modes for measuring the effectiveness of the towers, when only one defense tower is present. You need a strong boss to survive after the assault so you can measure the residue health points.

The main deduction is the firing rate which isn't disclosed in the game. It confirms that the Swarm towers are much more effective than the Squirt towers. And that it's always much more cost efficient to upgrade than to duplicate one. And since Swarm towers are for air defense only, we have to have a mixed defense with Sw towers. Though I manage to kill all flying creeps with Sq towers only except for the Flying Bosses.

Looking at the range data explains a lot of things. Why the DNA2 defense is so effective with a Bash tower inside, but doesn't work that well when putting other things inside, or to join the basic unit into larger chains. It confirms what I have been doing is right, wrapping the creep's path around Sq towers, which seemed to be in conflict with the square defense.

Trying to force the creeps around your tower for as long as possible, the basic pattern is a cross build from squares, with your tower in the middle. You try to block the creeps to run around your cross. For maximum range of an Sq (90), the size of a cross is 5 squares in width. For short range weapons such as Bash towers (50), the cross degenerates into a single square, which explains the effectiveness of the square defense. For long ranges, variations of the cross maze are possible, as long as the creeps are forced to run around the circle within range.

Frost towers are the big surprise. They slows down the creeps from a factor of 0.85 to 0.6. So for $200, you can increase the damage of a tower by 1/0.6, or 66%. This is in a way much cheaper than a Boost tower, which cost $500 for 50%. Though they work differently. The frost towers slow down the creeps that pass through, while the Bo's increases the damage of the towers touching them.

Before building the most effective maze, we need to know what weapons are needed and how many of them. Oh yes, it's hen and egg, as the maze determines the total damage that a tower inflicts on the creeps.

Anyway the Flying bosses are one of the most difficult to kill. It turns out that you need 4 Sw6 (Swarm tower level 6, or Storm tower) and 4 Sq6 with Fr6. You can have more Sw and less Sq but the Sq are shared with ground defense. With Boost towers, it's never worthwhile to build more than two towers. So all you need is two Sw6 and two Sq6, all touching two Bo5 (50% boost). Fr6 has the same range as Sw6, so you probably need two Fr6 to cover the two Sw6's, ensuring a consistent 0.6 air speed reduction.

Spawn creeps are the most difficult to kill land creeps. When you kill one, two little spawn creeps are born with half the strength each. So the Spawns are effectively twice as strong as any others in the same level. It also means that you can not kill them with a short range weapon no matter how strong.

So the defense is based on three crosses, one for Ba (which degenerates into a square), and two for the two Sq, which are sufficient for land defense as well as air. You can do without Ba's but since they splashes (killing everyone within range), I think it's the key to high score by sending in creeps earlier. I doubt if you can do without Sq's because given enough time with a proper cross, it provides the most damage per unit cost.

So the basic strategy is for the Ba to at least kill the first generation Spawns, and then the other Sq's take over. Each Ba can deliver three blows when creeps (speed factor 1) are forced to run along it on all 4 sides. The upgrade sequence is something like this, the first is the level number which are spawns.

6 sq3
13 ba1 sq4 sw2
20 ba3 sq5 sw3
27 ba4 sq6 sw4
34 ba5 sq6 sq5 sw5
41 ba6 sq6x2 sw6
48 all +80% fr6
55 ba6 sq6x2 sw6x2 +100% fr6x2

Initially you have to merge a square, as in the DNA 2 defense earlier, with a small cross 3 square wide. Any larger you are wasting resources and wouldn't survive the attacks. When you reach sq6 you have to knock down the borders and enlarge the cross to 5 square wide if possible. When you have two sq you merge the two crosses together side by side overlapping. The total range are halved due to overlapping, but the fire power is doubled there. This also allows mounting space for touching Bo's and Sw's. The first Sw must be in the dead center of the desktop where the Flying bosses pass through.

The other way to force creeps running around your guns is to sell a Pellet tower to open up some 2nd passage and block the 1st passage. It's no fun as it's increasing slow to sell towers. You might save time by having three or more openings so one is open, one is closed and the other is being sold. But I don't think it's the road to high score, which needs a high kill rate. My strategy kill everything without selling and juggling except for the 2nd last Morph Bosses. You may go to the scoreboard to see my humble scores - theplayer, and there is a group score with me in it - players.

Now perhaps when there's nothing to discover, I might go back to my real desktop, top score or not.

Thursday, November 15, 2007

Desktop Tower Defender

I stumbled upon this game and I was addicted. This is the winning strategy.

If you like Ages of the Empire but have no patient, this is for you. There are sufficient variations to apply your warfare theories but the rules are limited so the game can be defeated with not too much practice and research. So, it won't last forever, and you will be back to your real desktop very soon.

The weapons:

The Pellet tower is like Napoleon's foot soldiers. They can hold their lines well, their fire power is decent, but they fire too slow. You needs lot of them. Although their damage/cost is good, the (rate of damage) / cost is poor compared to the Squirt Tower which fires much more rapidly. They do not worth upgrading for more damages. However, like pawns in chess, they are very important. They are cheap, they are plenty, they are disposable.

The Squirt Tower is like machine guns or cannons. The rate of damage / cost is best as they fire non-stop. This is the main weapon of choice.

The Bash Tower is like a land mine redeployed in a short time after every explosion. Or it's like a fixed cannon. It has the best damage/cost ratio. It fires very slow but it damages enemies all around it. It's complements the Squirt Tower.

The Swarm Tower is like anti-aircraft artillery. It fires 4 missiles at the same time. It's a little slower than the Squirt Tower, which is for air and ground, while the Swarm Tower is for air defense only. I'm sure this is necessary. In the beginning, Pe and Sq are good at defending the first wave. When all the weapons are upgraded, the Sq seems to be increasing effective. There is a strange value for the last upgrade. It is apparent that it's better to build another tower than paying for the final upgrade. Anyway, one tower is about enough to kill off all aircrafts, except for the flying BOSS, which are almost impossible to kill. But I'm getting there.

All other weapons are not worth it. They do not have sufficient damage at the final upgrade. Just the Sq and Ba can get the job done. The dart tower is pretty good at the Groups but redundant when you fire power increases. I still don't find the Ink Tower effective against anything. The Snap Tower is just too weak for the big Bosses.

One useful piece is the Frost Tower, which slows your enemy down.

The Boost Tower is only useful if you have several towers placed around it. It's may be useful in the final stages when you have a lot of money and a lot of weapons. For example, it only make sense if you have three Sw towers put together to use Bo. Otherwise it's better to buy another one.

The basic strategy is to slow your enemy down to absorb fire. It's the classic square formations to defend against cavalry charge. For the desktop, I came up with the DNA2 defense based on this formation of Pe's. Obviously Pe's are used because they are the cheapest. You replace some Pe's with other weapons, and put others around it.

I think it's the cheapest way to get your enemy run the most, taking fire at all sides, it's also the most compact in terms of area.

Of course you don't use only one. The pattern can be repeated indefinitely, can be packed very closely to fit your desktop defense space. You can rotate it, flip it, to form long strands something like DNA spirals. Typically you shape your strands so you have plenty of spaces in the middle of the desktop for deployment additional weapons, typically air defense.

Actually you don't need anything else but Pe's in the DNA2 formation. You don't need rapid fire Sq because 10 Pe's firing at random is as good as a Sq. However, the Spawn are pretty good at spoiling things. Distributed fire by Pe's cannot deal with Spawns effectively. Every time you kill a big Spawn, you get lots of little Spawns. There's no way to really slow them down and you have to kill them several times. So you need concentrated fire power other than plenty of Pe's.

It should be noted that the Spawns can pass through the gaps some of the times when the squares are barely touching. But when they pass through one formation, they will be caught in the next. Just remember to block those vulnerable corners where the Spawns can escape to their home base. Even for this weakness, the DNA2 is still much more effective when the enemies have to pass on all 4 sides of a middle square.

The deployment:

Basically you block your enemies so they only charge through your square formations. Obviously the first middle square should be a Ba. Then you need a Sq concentrated at the first corner of entry. The position is crucial. If you put it on a middle square it performs poorly. It shoots everywhere instead of concentrating on where you need it. It's optional to have a second Sq at the entrance corner of the 2nd DNA formation. Typically Spawns pass through the 1st formation will be killed in the 2nd.

The upgrade strategy:

A few of the DNA formation can kill most enemies, with just a Ba and two Sq's. You want the most concentrated fire power. So you upgrade the Ba and the Sq on the same first DNA formation as soon as you can. The 2nd Sq should be one or two upgrades behind. I think on the final upgrade, the Sq are more effective with rapid fire, but of course the Ba's damage is impressive. If you survive the initial assaults, it doesn't really matter you upgrade the Ba or Sq first, as long as you don't upgrade all two Sq first. Save some money for the Ba.

Also you need to upgrade the Sw's regularly for each air assault. When you reach the final upgrade, you should buy yourself another Sw just short or the final upgrade. But I'm not sure the final upgrade is useful. It looks like it's better to have two instead of going for the final upgrade.


With the simple strategies you can kill most enemies except for two types of Bosses, the Morph Bosses and the Flying Bosses. Some other bosses are pretty hard to kill too. With mobility, you can certainly kill everything on the ground.

You can trap your enemies within your DNA2 formations by blocking and unblocking exits. They just run around absorbing fire. Therefore only one Ba and one Sq or two will be sufficient.

For mobility to work, you need two strands of formation. When you block one all the enemies have to go back for the opening in the 2nd strand. Timing is very important because unblocking becomes increasingly slow. You want to keep all enemies running pass your Ba again and again. You need very long strands, with 6 or more middle squares each. So you have plenty of time to unblock and block your exits.

Ultimate defense:

I can kill everything except for the flying bosses, which you cannot slow down. With 4 final upgraded Sw I manage to kill 2/3 of a flying boss. So I'm close. I'm not sure Sw is the way to go. Super guns in form of Sq are pretty good. The Bo's are pretty effective and money saving when you have a bunch of Sw and Sq trying to shoot down the flying bosses.

I have no idea how the other defenders defend. I looked at the top score once and the winning pattern is rather misleading. The person could be hiding his tracks in the final stage by selling things and buying things not needed.

I'm sure there are totally different strategies. I rather not look at them because it's part of the fun. I prefer my style, more like a warfare strategy game than shoot them down types.

Tuesday, November 6, 2007

Google blogroll released

Of course it only make sense to generate blogrolls within Google reader - you list the blogs you read in your reader. Google reader has clips to allow you to list the feed items, but not just the source as in a blogroll. Now the Google blogroll is a slight modification of the clips, in turn is just some particular display of a feed.

I have already done a very flexible feed displayer a couple of months ago. One use of it is for blogrolls generated from Google reader. It's a lot more flexible because it's a client side script, it's a couple of months ahead too.

Wednesday, October 31, 2007

The essential laptop repair tool

What takes it so long to design a desoldering tool that works?

The weakest link on my laptop broke - the power connector. After getting a set of precision screw driver from Lowes, I dissembled my laptop for the first time. I hope it's a simple job to replace the DC connector. But I was hopelessly wrong. The DC connector contacts needed resoldering. To get to the system board, I needed to take some components apart first. I kept unscrewing things, hoping the next screw would be the last. But I ended up taking everything apart, with little hope of putting them together correctly again. There are so many bit and pieces here and there, connectors all over, and miniature screws of different sizes that I couldn't even see properly with my naked eyes.

I took everything apart, just to find out that I could not clear the DC power connector's soldering holes. The tiny holes are filled with old solder. I could not insert the connector into position to resolder.

My classic solder sucker, in the form of a syringe, never really worked. The recoil action will pull the tip away from compact electronics, nowhere near the holes to be desoldered. I saw this new type of sucker on the Radioshack website, and something else. It's promising so I went to have a look.

I saw some standalone rubber like squeezing pumps, which make a lot of sense compared to plungers. But I don't know if there is enough suction. Then I checkout this monster combing a pump and a high wattage soldering iron. It just make so much sense. My only reservations are that if a lot of heat is needed to apply to the board, and if the board is more likely to be damaged. The other question is if this is any good, why take it so long to see something like this?

I think a lot of designers don't like to be seen holding a soldering iron. Many hobbyist don't want to be associated with repair technicians. Repair technicians are proud of their skills. So nobody needs a desoldering tool that actually works.

Perhaps it's the cost. The classic plunger last a long time, suitable for the salary and budget of repair technicians. Rubber squeezers would have to be replaced frequently. Now this monster cost more than a standard soldering iron. In the past this wouldn't be popular. But now, material and things are so cheap that a soldering iron cost next to nothing, and the two in one desoldering cost next to next to nothing.

I can vouch for it. Nothing can be more compact than a laptop. I just heat that thing up, apply solder, release the pump, and the soldering tags on the board are clean as new. What took it so long to appear on the market? Though it can be dangerous. If you squeeze the bulb by accident, steam and molten solder will blow out.

Now laptop repair or upgrade is so simple after all! I was so surprised to find out that Dell published excellent repair guides on their website. I wasted so much time searching for repair guides on the web, and taking things apart myself.

Without the guide it's hopeless to put things together again. Dell listed all the screws sizes, their numbers, and where they should be used. Dell also listed the sequences to do things, for example, if you want to get to the system board, what else you have to disassemble first. I did managed to put everything together easily. But since I didn't follow procedure to take it apart, I made some mistakes. The score:

1 screw missing
2 screws unused
blue tooth module damaged

The laptop is working fine without the screws. I never used the bluetooth module anyway. A working laptop again - priceless.

I think my time are wisely invested. The laptop was never used as anything other than a browser, and a video player. I did some work on it but I prefer to work on the desk and a desktop is much more economical to upgrade frequently. A desktop is always more powerful than a laptop too.

When my laptop can't keep up with windows and fat software, I can always load linux, which would turn it into a faster browser and video player. Beats the $300 laptops at the moment.

Saturday, October 13, 2007

Book review: The 4-hour work week

Tim has a blog to promote his book. I was reluctant to write a review on his book or his blog, because a book once I trashed, kept rising fast on the Amazon rank. His did get a lot of publicity everywhere, including TV. His book did get to the top of the New York Times best sellers' list. I was really disappointed by the non-fiction buying public. Don't they watch enough infomercial already?

I do agree with him on a few things. His favorite cities were San Francisco, Tokyo, Frankfurt and Buenos Aires, in descending order of living expenses. I would add London on top though. I also share his taste of Trade Joe's wine, well received by wine experts, but at only a few dollars a bottle.

First, let's look at his qualification. He called himself a serial entrepreneur, but never reviewed what his past or current business were. Understandably, his wasn't proud of his businesses, otherwise he wouldn't use the term serial. If you get something big going, you want to build it up to rival Bill Gates, Google or many other smaller flies that the big guys will acquire.

He's in the business to make money. Not that much obviously, because he is arguing that he's the new rich. He has plenty of leisure time, a very high quality of living. That's not surprising if he enjoys wine at a few dollars a bottle, while in a classy restaurant you don't even get a glass.

How does he qualifies to write such a book? He does have an ivy league education, and a short time as a corporate slave, that's about it. Obviously to work 4 hours a week to need to get some business going. But then you don't even need to work 4 hours. I think there's a misunderstanding by the book buyers. He's telling you the methodology to work 4 hours a week, not how to make enough money so that you don't need to work so much hours!

It's so obvious to me that the book is another of his business. He's doing it to finance his working 4 hours a week. But he's not telling you how to find money. Do I need somebody to tell me how to work 4 hours a week when I have enough money?

It look so like infomercial, for example, the bald guy who sell you a stock market analysis and trading software tool that guarantee you to make money. But if you get an edge in the stock market, do you really need to tell others charging $50 each? But who cares, USA is a self help country. If you have something to say that will improve people's life, earnings, or wrinkles, the infomercial will work, books will sell.

But I understand. The infomercial guru, who wrote books about non effective drugs, and effective alternative treatments that the drug company don't want you to know. He was investigated by the FDA, banned from doing many things. He found a way to get back to American satellite TV via a British broadcasting company. He sells new books about weight loss, but bundled with his old alternative medicines books for free, but most of the time he talked about the old books rather than the new one. Obviously he got around some loop holes to continue his ways. Accidentally finding myself watching him when his ad popped-up, he did have some points. But it was like brain washing.

So how many people will treat books and infomercial as brain washing Trojan horses. Your teacher says you always have to have a critical mind. You should be critical before you open yourself to possible brain washing. It's easier to be critical before watching or reading than while you were being brain wash. When you were eating popcorns, you will be much less critical about the movie. But then, if you don't read it for yourself, you may never know, or miss out. That's the whole point. People are afraid to miss out big, but not afraid to to lose a few dollars to buy a book. That's how authors earn big money.

As for the content, he doesn't review much outside of the book, or he doesn't have much to offer. I didn't read it, don't want to buy it as a principle. The big things he used for promotion was - read email only twice a day! Oh my god! I couldn't agree more. People used to do it when they login first thing in the morning, and logout when they go home, before Windows or Dos. But do I need to buy a book for this? Get a paperless life by opting for online statements. Who doesn't? Pay a dollar to get yourself off junk mails. Well, I don't know that. Maybe the book is worth it after all. Wait a minute, what's that to do with working 4 hours a week? Light years apart.

As for the underlining big picture, there's nothing new as opposite to what Tim says. Living simple was already a movement, or a trend, since the last boom and bust economic cycle, maybe a lot earlier than that. Maybe the boom of the late 90's made people forget all about it.

Outsourcing is big, but he promotes it down to personal level. Pay somebody to do your laundry for you for each piece of work. Pay a peanut salary for an well educated Indian as your remote personal assistant. Advertise on Craig's List to find somebody to cook authentic Curry Vandaloo for you for a few dollars a meal. Most of these won't work for the majority of people, or, it wouldn't worth it.

I think he's big because he used the Internet quite well. He has a huge geek following as he called himself the new rich of the digital age. Every webmaster big and small dreams to be him, harding working at all, spent most of his time flash packing all over the world. So he got great exposure on the net, all giving him positive mentions without discussing substance of the contents.

Excuse me, but I have to pick on him about his substance. He made videos and that's suppose not to be easy to forget. One video is about teaching pen flipping, that's what all students in Asia do. Is he real? They are doing it for generations already. If you give a Japanese retired CEO a pen, he will flip it unconsciously. The other video is about how to wear a tie properly - the Windor knot. Oh please! Every British male do that, as do all males the world over except for Americans. It's the same thing that the American turn cricket to baseball, and soccer/ruby into football. You won't find any other men if the world who would wear an unsymmetrical tie. If you do, he is the sort of person who would be proud of the American way, and he will call it the American style.

Let me share with you a practical proverb. Doing most things is like paddling against the river flow, if you don't go forward, you will be carried backwards. By all means look for a balanced life, but trying to keep still on a flowing river is not wise.

Thursday, September 27, 2007

Exploiting the ant algorithms

You can make use of the ants behavior to help get rid of them, or even use them to help you in productive ways.

As the insect terminators would say, we live in an ant hill. The entire neighborhood sits on hills, with large amount of steep, unbuildable spaces around houses that you don't have access. Even if you get rid of all ants around your property, if your yard is in any way still inhabitable for the ants after the chemicals subside, they will certainly come back. There's an unlimited supply of them.

At first I used to spray all around the house and yard with chemical spray that is attached to the hose, suitable for lawns and plants. It's effective but it doesn't last. Also it's also difficult to isolate yourself from the insecticides. You breath the water vapors with chemicals in it, the vapor blow back by the wind all over you. Then we call in the terminators. It's not any better, because they recommend to spray for you every three month standard. It's not termination. In out area, the standard won't work. Some recommend to spray every other month, using expensive but safer chemicals.

Basically it's a waster of money. When I don't see the ants eye to eye, they don't bother me. Not that they destroy anything significant. When there are two many of them coming to attack everything, I can just spray around. Just 10 min's of work, using a whole bottle of lawn insecticide. And then I went for a decontamination shower.

But I didn't do it anymore. I observed that the ant algorithms are very simple:
* ants only live in hidden dry areas
* ants need water and food
* ants travel in the shortest paths

My new strategy is draw them out, find the colony and kill them all. You don't really need to draw them out. After intense heat wave, they will go out in search of water. After heavy rain, they will move their flooded colony to a new dryer place. When I want to draw them out when I want, I would flood the boundary of the yard or any possible dry spots around the house. Also, dog food pellets are the best bait, never fails, while the ant baits with poisons in hardware stores never work.

Once the ants need to go out, they are very much exposed. They like to travel on flat surfaces without obstacles, even if they are exposed out in the open, under intense heat and sunlight. They don't like to travel across plants or soil, which are obstacle courses compared to flat stones or concrete. So if you fill any gaps in your stone or concrete pathway with paving sand for example, the ants will certainly march along the surface of the pathway.

Other favorite places where ants like to travel are fences, the outdoor damp prove course several inches above base level of the house.

Ants are easy to find in these areas in plain sight. They just don't like to hide under grass or ground cover. Follow the line and you know where their colonies are.

To kill them I use a hand operated spray, with chemicals that can be used on fruits. It doesn't take much spray to flood their colony with insecticides. And if you like, you can spray on the whole line of ants sometimes a 100 feet long, often made up of most of the colony.

The ants come because there's some food. It's time to harvest the fruits before the ants. Or your sprinklers do not cover all the lawn, with some dry spots. Or you have some cracks outside the house, allowing the ants to get in for a cool dry shelter. Without ants, these spots are hard to find. Ants are just so useful!

Tuesday, September 25, 2007

Mexican Drip Irrigation

My house has a standard 1/2 irrigation system. However, the previous owner must had designed the layout and laid the pipes himself. Nothing is right. Grass is supposed to grow right up to the edge of the house and the fences. It is extremely difficult to cover all the areas to be watered.

But that doesn't bother my gardener. He adjusted all the sprinklers so that all green things are covered. He doesn't care how much water is wasted. He doesn't care about water damage to the stucco. Those are not his problems. I changed new quality spray heads and adjust the spraying distance without success.

Out of frustration I changed to drip irrigation gradually. Initially it looked good. Though the 1/2 underground pipes are fixed, I can now place 1/4 tubes over the ground wherever I wanted, so the tiny, precise spray heads are right next to the plants. Can't do anything about the standard pop-up sprinklers, but with the help of fixed drip irrigation spray heads, I can cover grass that the pop-ups cannot.

The problem is, the 1/4 adapters got blown off by the water pressure, or the spray heads got blown off. But I cannot install a pressure reducer that is usual for drip irrigation. My system is mixed. Though this could be done if I change over completely. Luckily I didn't. Silly me. Recently, when I replaced the shut-off valve to the yard, I discovered that my pressure regulator deals with water to my house only. All other water are not regulated.

So my irrigation system was at over 100 psi. No matter the electric valves cannot be adjusted and so short lived. No matter something burst all the time. No matter all the sprinklers and spray heads seem to be out of control with water spraying everything. No matter it was so difficult to adjust the volume of everything. No matter that when something was wrong with my neighbor's swimming pool plumbing, we both burst some sprinklers together.

The major problem was my gardener, his successors, and their whole team members. When they clear weeds they will clear the over ground 1/4 tubes too. Or they will cut the spray heads off without knowing. It's not surprising because often they destroy indestructible pop-up sprinklers with their mowers.

Gradually I moved back to a standard 1/2 system, leaving nothing over ground to be destroyed. My 1/4 system resigned to the garage.

Until recently it dawned on me that I was visiting the wrong department for drip irrigation. I used to get everything from the garden center - the 1/2 to 1/4 adapters, the tubes, the spray heads, the connectors. Either they are too tough to join together, or too easy to connect but will be immediately blown off when water pressure is applied.

I also used the standard plumbing department for 1/2 tubes and connectors. I tried to add something rigid, like splitting one outlet into two, before converting it to 1/4 at the end, which is much less rigid.

It suddenly dawned on me that the ice making, 1/4 tubing department, that I visited many times for my reverse osmosis system, are compatible with the 1/4 drip irrigations. I never realized that the drip irrigation uses standard 1/4 tubes. That made a lot of difference.

Now instead of the T's and couplers from hell, I just use quick connect. It's a few dollars a piece but saving my fingers is priceless. The 1/2 to 1/4 adapters are industrial strength, not plastic toys as from the drip department. Now designing and installing the system is a joy.

Now I have more tricks to fix the system in place. In the past I rely on stakes to hold the tubes and spray heads. Now I can use rigid 1/4 tubes as far as I can. In the past my stakes get bigger and bigger so as to survive the onslaught of my gardeners and their teams. Now I use custom made acrylic pieces to hold the tubes and spray heads, and glue or screw the whole thing to something rigid. As the acrylic is crystal clear. The whole thing can look good or not visible at all.

One final thing. All spray heads are directly pushed or screwed into the end of tube directly. I will now only use the screw ones which is easier. And before screwing them into the tubes, I apply some gorilla glue. In the past you can hardly reuse the spray head this way. Now all the spray heads are mostly attached to half an inch of tube, to be pushed effortlessly into quick connectors.

Now I can add something, change the spray heads, replace damaged materials fast. Don't know why don't sell it that way, instead of in 3 separate areas of the plumbing department.

Saturday, September 22, 2007

Scam: reverse osmosis permeate pump and valve

Not exactly scam, but depends on who and how they sell it. The permeate pump is certified, made of harmless material, and won't fall apart, but it is the magic bullet as claimed in the manufacturer's Aquatec website? No. But since they only sell it to distributors, they give you no specification and they are not responsible how you use it. But now these companies know that nothing can stop people selling things to individuals on eBay, they are a bit careful on their website, in order not to develop a scandal.

Many pumps are sold to retrofit existing systems. But notice the 75 psi feed input on the main diagram on their website. If you haven't got that pressure, it very doubtful it will work well. And if you got all that pressure, it's doubtful if you need a pump to get good results.

Standard main water pressure depends on water district, but should be 50 psi, which is the value for sprinkler specification. You may get higher pressure if you live uphills in individual houses, where the water pressure gradually decrease downhills to 50 psi for houses at the bottom. In this case you need a pressure regulator, which is usually factory preset to 50 to 60 psi, with 75 psi as the absolute rating. So basically, now that the permeate pump isn't new anymore, Aquatec is basically saying you need a booster pump without admitting it. A booster pump cost twice as much and gives you a lot of improvement if your feed is just 50 psi. It's crazy if you use a booster pump plus a permeate pump. Since I have 75 psi without the need for a booster pump, I'm OK. It wouldn't work well for 60 psi, and I can prove it.

When the tank is empty, that is, no back pressure to the membrane, the membrane sees the full pressure of about 70 psi. The pump is supposed to maintain the back pressure to at most a few psi so the full 70 psi pressure is maintained at all times. With the right flow restrictor, there should be enough pressure and flow in the brine/concentrate to do that. But I found out that the recovery rate have to be high at about 25%. Which means that the drinking water to waste water ratio is 1:3. This is far from the usual 1:4, or 20%, and far from the specified Filmtec membrane recovery of 15%.

But all is not lost. At 70 psi, even 25% recovery gives 98% stable rejection, which is the same specified rejection at 50 psi and 15% recovery. So with a virtual booster pump, and a permeate pump, I can't get better rejection but I waste half the water, 1:3 recovery instead of 1:6 recovery.

It won't work if you don't have 75 psi main feed. Say at 60 psi feed, you have about 50 psi across the membrane, and clearly at this pressure, you need 15% recovery to achieve anywhere near 98% rejection. 25% recovery is far off.

It's doubtful if you need any pump when you have 75 psi pressure. A 75 gpd membrane becomes 110 gpd which is a hell lot of water. But since the pressure is constant across the membrane, it's easy to design your system, and the performance is guaranteed under all circumstances. In other words, peace of mind.

In pumpless systems, basically the water is excellent when the tank is empty. Then the water tend to get worse as the tank fills up, or you waste a lot more water without realizing it, that's what Aquatec is trying to market their pumps. With typical usage, the system works most often when only a few cup or a kettle of water is being drawn from the tank. The water is worse or wasting most water when the pressure across the membrane is often 50% to 33% of an empty tank.

Actually I would like to write software to design residential systems. Dow has free software but far too complex and did not give out parameters for the residential membranes. So I couldn't do anything but to use 75 psi main pressure. The pressure is constant and everything is constant so it's easy to design.

And now the cutoff valve. It's not cheap at 1/3 of the pump price. But does it worth it? Nobody claims that it's necessary but say enough that you will buy it. I was surprised to find out that the valve don't cutoff at 90%, but about the same as the old valves about 66%. I talked to the distributors and manufacturer and it seems that they are well prepared. The distributor send me over to the manufacturer, who promise to test it and replace it if it's defective. But I am not to expect 90%, but 85% depending on pressure.

I almost sent it off when I realized that now the cutoff pressure of my tank will be the main pressure of most people, at 50 psi. It will be crazy to increase that to 65 psi. I don't need that and the pump may not work at that pressure. Also, the valve turn back on at 30 psi, giving 20 psi of hysteresis so the system won't turn on and off whenever people drawn a glass of water or a kettle of water. I don't know if my old valve do that. But since the new valve has JG connectors that are easy for me to measure things, and that the tubings are fitted already, I rather not go back to the old one.

Previously I have doubts about measuring pressure when water is flowing. But I find that it's very accurate, the dynamic pressure into the tank equals exactly the static pressure when the tank is isolated. After all, what else can it be? Now I left the pressure gauge dangling in a T piece somewhere in the water path. And since I needed a tank shutoff valve as an adapter for the standard gauge, I can shut off the valve so the gauge isn't in contact with potable water when not in use.

Friday, September 14, 2007

Camping tech

Most CA state camp grounds have free Wi-Fi access. It's a simple thing to do but made me think of an unrelated question: can we be modern nomads? For the rules, state parks usually have 1 or 2 week maximum stay per camp site, 1 month max stay per year within a county. It's not much but there are local sites that do not belong to the states, and there are federal sites. And there are 52 states!

But would you do that? Kids need to go to school, and that's that. Though home schooled kids aren't that rare, so moving every other week may not be too bad.

I love outdoors. Half a lifetime ago, space was so precious that I rather go camping when I could, even in tropically wet weather, walking for hours with all equipment on my shoulders. Tents weren't even draft and water proof.

I touched a tent again a couple of years ago. I saw one small and cheap on sale and picked it up for earthquake preparation. And forgot about it.

It turns out that Rangers looking after the camp sites have rather dangerous jobs. For popular beaches near urban centers, there's the drunks. Now for remote sites, they often go into heavy gun fights with the pot growers, with millions worth of pots at sake. Other than those, crimes usually aren't premeditated. You don't plan to rob somebody random in remote areas. Without premeditation, it's hard to get away with it, such as the Yosemite killings. For the good part, no where else in the world you get to live in a free gated community, with armed guards until 10 pm, then total lock down until dawn. Here I bet criminals can't run, they can only drive. I doubt if anyone will try to do the hard work when they can't get in or get away with a car.

Tasers are going to be very affordable, may be as popular as pepper sprays. You can also draw up visible and invisible boundaries with infrared, laser and lots of cams. But for the moment, camping is still a very much friendly family affair. The rangers will check you up at least twice a day. When the sites aren't too busy, they will remember you if your clean car looks out of place, thinking that you are newbies and needs extra attention. Sites owned by rich counties are even better.

The bad thing about camping in CA is that you are basically living on dirt. You don't have a lawn if you don't have sprinklers, unless you camp by the river. But most "rivers" dries up in summer, while winter is too cold. So you have to have tents for bed rooms, that you only get in for sleeping, when you are presumably clean. You need separate living spaces, sheltered from the sun, and preferably from insects. You also need changing rooms too. You don't want to walk in and out of bedrooms with feet full of dirt. You also don't want to kick everybody out of the living rooms just to change into some special gear, such as swim suit. And for the beaches, you need to bring a cabana to the water front.

Modern materials are amazing. My cheap made in China tents and canopies has very light flexible support poles, wafer thin fabric. But still I couldn't manage to make a hole in anything. All zippers are still working. The fine insect screen didn't break at all even after attacked all night by raccoons. I can carry all the "rooms" easily in my trunk, and I can erect huge canopies alone.

That's why I don't fancy RV's. It's two cramped in comparison.

As for creature comfort, you are spoiled for choice in chairs and beds, king size down to twin, high tech air bed, or self inflated. Satellite TV dish are portable. If you don't like the free WiFi access, there's the true satellite broadband service. Food is always great, briquettes are always better than gas grill back home. The match lighted ones are as convenient as butane gas.

Now the dreaded loo. Public showers aren't that bad. Typically hot showers are coin operated with a large gas boiler, giving decent pressure and volume. If you are fuzzy you can bring your own shower tent. With solar heating and battery pumps, a private shower room can be barely decent. Of course RV's all got these, and with electricity hookups, RV's can afford decent heaters and powerful pumps.

The public toilets are very clean, but only in the morning right after they cleaned it. At busy seasons it's terrible after an hour or two, even though most campers try to minimize their mess. Imagine McDonald only clean it's toilets once a day! Some more remote places are called environmental sites, where there are only so called chemical toilets. Terrible! terrible! I would rather die of blocking.

RV seems to be a lot better with it's own toilet. You still need to deal with the mess but it's your own toilet and your own mess.

But not anymore. It must be fairly new, because the majority of toilets for sale are till big buckets. You store your mess in it, may be put some fragrance in it after every use, and god knows how you empty that and clean that afterward.

Now there are high absorbency powder to turn liquid waste into jelly, and semi solid waste will become more solid with odor reduced. Instead of a bucket, you empty into a toilet seat with big plastic bags underneath. Whenever you want, you seal the plastic bag with another, throwing the whole thing into trash. I suppose the concept isn't that new. But now all the materials are biodegradable, the water tight plastic bags degenerates within 6 months. It was approved by everybody, endorsed by me. Now a toilet/shower tent is lighter than a typical camping chair. You can have your out house wherever you want, with a view if you want. The worst nightmare becomes a joy. RV's aren't that good. There's totally no mess to deal with. The plastic bags aren't cheap, but I'll still go for it if they sell it like crack.

Maybe someday dry toilets are the way to go back home. The flush toilet has been haled as a great invention, but may be a big mistake. Dry toilets do not waste water. A out house in the yard is no problem at all. You can have one for each in the family if you want. For apartments you can have ventilation rooms, which are easier to build than conventional toilets. Perhaps doing it in a slightly larger closet is good. Houses can be smaller without the toilets, and it's simpler without all the plumbings.

Wednesday, September 12, 2007

The perfect geek material

I never like wood, but I thought it was the only material that you can custom in your garage. Over the years I have a circular saw to cut 2"x4" beams for play things, now the saw is being recalled. I also have a little power sander to smooth the coarse wood so as for the surface not to be too tough for the touch. I once brought a jigsaw to build a custom corner table. I thought it was good but it got thrown away. An fake antique table replaced it.

I was looking for something to replace the cardbox in the yard, when I come across acrylic. I thought it was perfect. It's look like glass, lighter but tougher. And you can cut it to size with a knife. Perfect, just what I needed. So I designed a rather complicated box with lots of compartments, doors and openings in it, using a free CAD package.

I fit my design into a 2'x4' flat piece of acrylic at 1/8" thick. When the piece comes, it was perfect. It really looks good, crystal clear. It was protected by plastic film so you cannot scratch it while cutting it. The thickness is just right. It's just tough for you to build a strong box. Any thicker cost a lot more, and any thinner it feels plastic instead of glass. But there's one catch. There's no way you can cut it with a knife, at least not a decent long edge.

So I brought out my jigsaw. It's tough work. It's very slow to cut through the acrylic compared to wood that is a lot thicker, which is expected. Also, you cannot make a straight cut with a jigsaw, unless you have a decent work bench, which I don't. I should have ordered custom cutting which is more expensive than the material itself. At least for the long cuts, I should use some help. But I soldiered on.

The good thing is that, at a right saw speed, the blade create just enough heat to melt through the acrylic, but not too much melting, giving a nice smooth edge. The saw dust are basically acrylic melted into tiny beads. It's everywhere but a lot more pleasant than wood dust and it's much easy to clean.

The bad - the unexpected jigsaw instead of a knife leaves me with rectangles big and small, all without straight edges and right angles! I know it would be a challenge to fit the pieces together. Also, the dimensions are more than 1/8" off after cutting. So I have to run through the CAD package to made alterations as I went along.

Luckily I brought some small right angled wedges to help to glue the pieces together at the corner, and some squared tubes to help with the squareness of my box. And I settled for some toxic solvents for a quick welding of the pieces, instead of using slow solvents and requiring clamps that I don't have, and don't know how to apply in small spaces.

You can imagine the final box is comparable to a cardboard box using coarse tapes to stick the pieces together. But acrylic is something. You can see the glue, it's clear but there are bubbles in it. It's hard not to use excessive glue for the uneven pieces. It drys hard and visible, but it's as clear as the acrylic. Basically it's just acrylic melted and reformed. The wedges at the corners are ugly, no sides are straight and barely square. No edges are smooth.

But the whole junk is rather addictive to look at. It's my junk and it's like glass suspending in glass. You got to enjoy the fine details, like uneven application of the glues on the edges and hinges. The curved edges, and the blurred edges just like glass. Best of all, it's tough and highly functional. If I order custom cutting for the large pieces, or invest in a bench saw, it would be perfect the 2nd time round.

I can imagine 1/16" thick sheets will be perfect for delicate things, such as custom electronic enclosures. You should be able to cut it accurately using knifes. Polish the edges and use thin glues that make perfect invisible joints. You can drill small accurate holes, or cut out large portions for a screen mount etc. You can order custom laser cutting for you name to stick on it too.

The major problem I had was needing a lot of motors with gearboxes to mount on my beautiful junk. It's just too expensive compared to the whole box, and looked ugly. You can get bare motors a lot cheaper, compact and powerful. But without gears and crank arms they are useless. So after exhausting the web to find something suitable, I cut a little piece of acrylic as the crank arm and drill a hole in it. I put the bare motor shaft in it and glue them together using gorilla glue. It surprised me that now it's a very tough crank arm! The rest of the problem is mounting the motor onto the box. It just need another small piece and screws to clamp the motor securely in place. Now even the motor mount and the crank arm are transparent and look good, with screw suspending in mid air.

I fell in love.

Prototyping down memory lane

It is also a story of what can go wrong went wrong.

Remember I needed some basic electronics for a useful purpose. So I went ahead to design and build a circuit. I want it to be battery or DC adapter operated, it's also a battery backup and charger. The backup and charger part turns out to be rather complicated, which explains my chargers are so bad. I can use lithium batteries and make use of a single chip to do all I wanted, but the chip is used for cell phones, surface mount with no leads, only tiny pads under the chip. No way I can deal with that by hand. So I give that up for the moment and the circuit is strictly Either battery OR DC adapter.

I actually never build much circuits. The kits on sale are rather tame. If they are any good they would design consumer products. Also, you just learn soldering if you build those. I did build something important once with a lot of chips with wrapping tools. With low power you need low noise, together with surface mount components, wire wrapping are way out of fashion. I hate using solderless prototyping boards. I don't need to test everything first. And it's too expensive to use the boards as the final product.

However, once upon a time copper becomes previous metal. So the prototyping boards with lots of copper strips disappeared. The best I can find is some rather expensive boards with just holes on it and a solder tag around it. (But somehow the PCBs plated with coppers are still around, but I have no patient for the slow turn around of making PCBs). I made the mistake of trying it assuming the lack of rails is no big deal.

Firstly, the real time clock and alarm I ripped off from a timer switch is too good, it worked on 1V instead of 3V on my circuit. I knew about it but I thought CMOS would work with wide voltages but not for that clock. So I added another battery to supply the clock and added a transistor to pull up the alarm signal up to 3V.

I chose components to minimize chip and connection count. But the choice of components off the shelf is limited. More importantly, I misread an unimportant part of my own circuit, the gates are to be repeated on all signals in the bus, but I allocated components and space just for one signal. So I have no chips or no space for all the signals. But I can live with that for a prototype.

Without ground and supply rails, the soldering is a nightmare. Every connection is by a wire, and I didn't have the magnet wires, insulated wires with coating that melts when soldered. So I have to strip every wire before soldering using a blunt, large soldering iron. When I brought the iron, I wanted one that is powerful enough to for thick electrical repairs, and also doubles for electronic work if I ever needed. So the tip always touch two chip leads when soldering. It's a nightmare. But I soldered on hoping to get out of hell as soon as possible.

At the end it was spaghettis over and under a plate in 3-D. It was hell. Worse, nothing works that surprised me. The IO drivers all don't work so I don't know what's going on. And I have only a hand held multimeter to trouble shoot. Funny that the main fault was laughable. I used CMOS design for the first time as my real circuit needed to be low powered. The basic quad NAND gates have different pin outs with the TTL versions!!! Just 1 in the 4 gates have different pin outs, but just enough to make everything not working. I vaguely remember that it was to differentiate that it is CMOS rather than TTL. But nowadays you will use the same pinouts, even if it cost you more to manufacturer. But now the CMOS pinout is history and you have to remain compatible.

And since the circuit was a hopeless mess of spaghettis, I had to find another fresh circuit board to start over. Luckily I found an ancient copper stripped board in my garage just enough to fit the chips that I have. It now looks better but still a lot of spaghettis, but less painful to build.

The circuit at least work as expected but a lot of strange happenings, like on and off of motors and LED's when not expected. The power on reset doesn't work as the microprocessor in the real time clock takes a few seconds to reset, while my own circuit resets for a much shorter time. Now it's a random start, but since I cut down the number of states due to insufficient space and chips, it's only head and tails.

The manual reset doesn't work either. I suppose the pull-up resistor is too large to save current. But I can always reset by touching the contact with a wire connected to ground or supply.

The unexpected on and off is due to a long alarm signal. I have a timer circuit to control the width of the pulse, and to isolated the alarm signal once activated. But I got it wrong assuming it's trivial. So I have to indulge into some Boolean math to arrive at an asynchronous finite state circuit with minimum gates, which have to be a modern classic. But I needed 3 NAND gates. So instead of blinking LED's to save current, some are not blinking to save some gates for the modern classic.

It's working now for weeks on two AA batteries. But very recently I found out that the sparks of a small motor nearby will cause the circuit to change state for certain. It's no big deal as I have to redesign the whole thing anyway.

The perfect reverse osmosis system

Perfect also means a good price :-)

The feed shut off valve is not enough. It takes forever to shut off the system and restart. I suggest to add a plastic ball valve right after the feed valve. Surprisingly, the ball valve carried at Lowes carry a cancer causing material warning, but it's sold along side NSF approved tubings. I would buy a valve with John Guest connectors. And since JG seemed to be patented, there's always a minute but ultra fine JG symbol somewhere, even though the manufacturer's name wasn't on the component. This is very typical. Manufacturers don't normally make all the component of an RO system. So they mainly sell to OEM's, unmarked or marked with the OEM's name. BTW, JG is also a company producing many components.

You can easily find NSF approved 1/4" tubing in hardware stores, for fridge ice makers. For the filter housings, what can go wrong? It's hard to check if those components are NSF approved, as most makers sell them to OEM's. And then the whole system is approved rather than individual components. But I bet all housings are made of FDA approved food grade plastics, and that any housing looks like any others. But I'm not so sure about the O-rings used to seal the filters. There are NSF or FDA approved O-rings on sale fit for standard housings. And there are approved silicon grease to be applied on the O-rings to seal.

There are typically up to 3 pre filters about 10" long for residential use. The main purpose is to remove chlorine which attacks the membrane. But I made the mistake of choosing too good prefilters. The worse mistake is to use a 0.2 micron ceramic filter. When I looked at the data sheet, the pressure drop across the filter is 15 psi, though at a very high flow rate which doesn't occur at residential systems. So at 50 psi input feed, you could lose a lot of pressure just across one filter alone. The filters to buy are Matrikx branded. They have a stable and clear line of products. They have a good name and a lot of systems use them (I guess). They provide datasheets. You can get the top ones at as low as $10.

The static pressure is easy to measure. A pressure gauge costs a few dollars from hardware stores. Screw it on a garden tap, 3/4", and you get the static pressure, when all other taps are closed. For 1/4" RO systems, you just unscrew the 3/4" adapter typical on gauges, and you can screw the gauge directly into a JG ball valve for RO tanks. Now you just insert any tube into the valve and you get the static pressure with the valve open. But measuring the pressure when water is flowing is tricky. If the water don't flow, there's no pressure drop across the pre filters. I've seen attaching a gauge to a T adapter. Water is flowing straight through and the pressure is seemed to measure perpendicularly to the flow.

Filtered drinking water is measured in gpd, gallon per day, while the stated flow rate for pre-filters is typcally gpm, per minute. So the stated pressure drop at the high flow rate may not apply at very low flow rates. Anyway since I cannot know this, I minimize the pressure drop by choosing suitable filters.

I'll start with a 5 micron sediment filter, if you water supply isn't that dirty. Coarser filter is associated with larger dirt capacity and less pressure drop, a few psi. Then the 20,000 gal carbon chlorine filter is a no brainer. If you don't really know how much water you drink, it guarantees you only need to change filter once a year. If you know, you save money and time because the chlorine capacity is a lot larger than other filters, you only need to change filters once a long time. I estimated that the water passing through my filter will be 5,000 to 10,000 gal, so I only need to change filters once 2 to 4 years, considering the chlorine capacity alone. It also good for filtering VOC if by chance you got it, volatile organic compounds, which are basically vapor gas that the RO membrane can't deal with. The pressure drop is less than 3.5 psi and the size is about 0.6 micron.

It just happened that I have a 3 stage housing so I have to pick one more. Another same carbon filter is OK but there are a lot of other choices probably for non RO systems. The mistake I made was picking a 0.2 um one with a psi drop of 15, making it unsuitable for RO systems. The choice is between certified lead or bacteria rejection. Since my water feed is very decent, and since the membrane will deal with that at sub micron levels, I settled on a 0.5 um carbon filter with 8 psi drop, with half the chlorine capacity. There is some cyst reduction, bacteria that isn't killed by chlorine. Other reasons are price and availability.

The most important component used to be the membrane. But as I said, pumps cost a lot more. The only membrane to get is Filmtec, certified for 96 to 98% rejection. And 75 gpd is the only capacity you want. Any larger the rejection drops to 90%, and any other brands is just as good. Even if you don't drink that much water, the tank refills fast. And since you don't have 50 psi as assumed by most components, you have more design flexibility and more choice of good filters. After all, it's just $30.

15% to 20% of water pass through the membrane, while the rest go down the drain. What makes water pass through the membrane is a flow restrictor on the brine side (waste water) of the membrane. Interestingly, almost certainly you have a wrong flow restrictor. If you have a 75 gpd membrane, waste water is 4 times that, arriving at about 800 mL per minute, which is the standard restrictor to use. But, the Filmtec membrane recovery is 15% rather than 20%, which requires a larger capacity. Also, instead of 75 gpd at 50 psi, you have 40 psi across the membrane if you are lucky. And for pumpless systems, you have just about 20 psi when the tank is almost full.

You don't have much control over pressure unless you have a booster pump to vary the input psi, and a permeate pump to maintain a constant pressure across the membrane. In my area we need a pressure regulator so I can increase that to 100 psi risking bursting pipes anytime, or decrease at the expense of weaker showers. Other than that you can buy filters with larger or smaller psi drops. However since you can't measure that reliably, I suggest to get a few flow restrictors, test the system performance with a TDS meter, pick the best one and return the rest !!

It's worthwhile to make a bypass path across the restrictor, controlled by a ball valve. It's called flushing the membrane when you by pass the restrictor, when all water goes to drain to clean the membrane. With JG connectors, it only cost you a minute to make. NSF components are not required at the brine side. Expensive systems used to have that path, and of course a timer to flush everyday for a few minutes. Membranes need flushing regularly only if your system is at 98% I guess. It's easy to achieve over 95% and never flush. At $30 it's worthwhile to change the filter every year. But if you use it for a few years for the full design life, you feel better to flush every few months or a year. The waste water are black, mostly carbon resides from the filters.

After the invention of the "affordable" permeate filter, it's clear that prior pumpless systems are toys. No matter how good your filters and membranes are, you only operates at a fraction of the pressure. The pump comes with a new hydraulic valve, which cutoff the supply when the tank pressure is 90% of the feed, and turns on the supply when the pressure drops below 70%. Since the membrane always see full pressure, the high cut off allows the tank to fill more water at higher pressure, and the on pressure prevents starting the system every time for a minute when you just pour a glass of water. The higher pressure is important if previously your RO water can't get through to the fridge to make ice. Previously standard valves cut off at 66%, leaving you with 33% pressure across the membrane. Permeate pump not only save you water, because less water flows through, you get longer filter and membrane life.

The final filter is always after the tank. I wondered why. Until one day I tasted the tank water and it smells and taste like rubber. I think it's a taste of the bladder inside for cheap tanks at least. It's also a good idea to filter the water when you drink it, not when you store it in a tank. I always use NSF certified Omnipure. Unlike Matrikx carbon block filters, which are designed for chlorine capacity and minimize carbon residues clogging the membrane, the final filters are carbon granulates design for maximum bad taste reduction. And I can vouch for it. These filters are smaller and have a much lower capacity as the drinking water to total water ratio is at least 1 to 4 or 6. But still you may need to change every 6 month instead of a year.

Cheap tanks rust easily on the outside and taste like rubber. They also lost pressure fast. There's a tire like bladder inside. When you lost pressure, you need to pump water out using a tire pump, measure the air pressure at 7 psi for typical tanks. Of course you better get a new tank when you lost pressure. The one to get is Flowmatic RO Pro tank. It's NSF listed. It's plastic so it doesn't rust, at least on the outside. The shape and color is a lot more pleasant than metal tanks. It fits well under the sink like a tall slim guy rather than a short fat guy with a beer belly. 4 gallon total is about the largest size that fit comfortably under the sink with space for other things. Practically you get only 2+ gallon for pumpless systems, or 3+ with a permeate pump. You also get a nice reserve in earthquake zones, enough for at least 6 people's maximum drinking needs for one day, but a least a few days for survival.

You have little choice about the faucet. A designer faucet cost you more than all the other components. Most people use Touch Flo faucets, look decent, cheap, and NSF listed. There was a settlement about lead many years ago. So they won't make the mistake twice. An ordinary drill and a special bit from hardware stores will make an extra hole on your sink, but depending on the material, I still have nightmares about it. But in my neighborhood, you can't find people to come in and drill a hole for you, not at a price you want to pay. You rather hire any heavy machinery you need from the hardware stores and blast everything yourself.

You need an air gap somewhere to prevent back flow of waste water. If the law allows you can use a check valve instead. Air gap at the faucet is a bad idea unless the faucet comes with tubings attached. It's a nightmare to attach all the tubes under the sink for a compact faucet at the very corner. You can use the air gap for the dishwasher. There are air gaps designed for that with extra RO input.

A digital TDS meter is a must. It's cheap and compact anyway. It's a measure of the conductivity of the water, which reflects directly the dissolved solids in the water. And since only the membrane can remove dissolved solids, the meter tells you how well your system is doing, if put together correctly at all. Typically for hard water, the supply is 400 ppm. If the RO water is 20 ppm, you get 95% rejection. It can be addictive. If you are a Monk person, it's worthwhile to get one of those that mounted on the sink to give readings continuously.

The other parameters that indicates your system is working correctly is a flow rate meter. But it's rather not necessary. You just need a measuring cup and a stopwatch. You get a good idea of the flow rate out of the restrictor and out of the membrane (when the tank is shut off). Restrictors can be inaccurate because of deposits, which is at higher concentration at the brine side.

Now there are low cost total volume flow meters on the market made of FDA approved plastic. You can program 5 reminders to change your filters according to total volume passing through. Nobody have a good idea how much water they actually use. Filters are either changed prematurely along with all other filters, or way too late. So the saving in filter cost will make the meter virtually free. You also get peace of mind. But you need to know the design capacity of the filters. But actually you need two, since there are three flow volumes in the system, the supply, the permeate (drinking) and brine (waste). Since the permeate and brine are never exactly 1:4 or any other ratio as designed, you need two meters to get all the three flow volumes, unless you have a good idea what the measured ratio actually is.

You need to disinfect and clean the system on a regularly basis, say once a year. The membrane is tricky if you decide to keep it for a few years. It can only tolerate low concentrations of chemicals and you need to pump the solutions through the membrane constantly for limited time. The details are on their website. I would rather flow it away after a year, or just soak it. To disinfect you need H2O2 from pharmacy and dilute about 10 times (check website). I'll soak it in the filter housing instead of pumping it for the recommended period. I have no pump. Then I'll put fresh solution in the empty filter housings, put the membrane back in it's housing, and turn on the feed supply. The H2O2 gets pumped across the membrane, but further diluted.

But if you actually bother to disinfect the membrane, you might just as well buy NaOH and HCL solutions from science stores and perform the alkaline and acidic cleaning steps as recommended.

Before the membrane, you can just as well pump higher concentration of cleaning and disinfecting solutions around the system, the tank, the tubes and the filter housings. Then using the tank to pump the solutions all the way to the fridge. Of course you need to pump a lot of fresh water to get rid of the solutions, and throw away the ice.

I think that's about it. Now the cost.

JG Valve's and T's $30
Filter housing $60
Filter 1 $10
Filter 2 $10
Filter 3 $15
Filter 4 $15
Membrane $40
Pump $45
cut-off valve $15
Tank $70
Faucet $30
TDS meter $20
Flow meter $30
Total $390

This is the retail component prices. If you buy in bulk and sell whole systems, you make a decent profit without much work. The JG connectors are a snap to use.

Tuesday, September 11, 2007

The perfect water

First of all, most reverse osmosis system are designed to have a recovery of 20%, that is, for every 1 cup you drink, you throw away 4 cup. That sounds a lot, but you actually don't drink that much water. Baths and lawns are a lot more wasteful. More so is flushing the toilet. Somewhere in the world use sea water or reclaimed water to flush. Also, bottle water, such as the famous Fuji water now widely available in Trader Joe, seems a lot more wasteful, pumping up deep ancient water and bring it over from so far away, in plastic bottles. Also many beverages you drink use RO water anyway. In good restaurants, if you don't want bottled water, they will give you tap water, filtered to taste good. It's worthwhile to include RO to avoid liabilities as bacteria and virus can hardly pass through. It's easy to achieve zero waste. You can feed the water to your irrigation system, or pump it back to the hot water supply.

RO systems used to be very expensive, $1000?, and still are, $500?. Some years back some cheap RO systems appear on the market aimed at the masses at $100. The performance in terms of rejection rate of total dissolved solids (TDS) is 85%, compared to top of the line systems at 98%. 85 is a lot less than 98, but filtering out 85% of what need not be there sounds enough for a try. The DS are basically the hardness of the water, naturally occurring materials. But here we use Colorado river which is really hard. And if something goes wrong for a short while in the public system, softening the impact by 85% isn't that bad. And if you can filter out 85% of the bacteria, that's good enough without costing an arm and a leg. It's not that I couldn't afford expensive systems. But like computers, I don't know what components they put in. You cannot test it, for example, how much lead it rejects. You have to trust them. But I rather not.

But the cheap pumpless systems are a joke. The stated performance is for full water pressure, typically 50 psi (sorry rest of the world). But once the system starts working, the pressure across the RO membrane falls. These systems typically stops when the tank pressure reaches 30 psi, by this time the pressure across the membrane is only 20 psi, a fraction of the stated performance.

Typically small manufacturers don't know what exactly happens as the operating points drift away from the optimum point where all the components are guaranteed. But as long as the final TDS reading looks good, they are selling it. Typically, the rejection rate maintains at low pressure, at the expense of wasting much more water! Not just 20%, but 10% and less.

To control the pressure, you need a pump. But pump's able to deal with 50 psi are not toys. Just a booster pump cost more than a cheap RO system. The alternative is to use an open tank and let the RO water flows into the tank slowly. So you are fortunate if you are a fish. For aquarium applications, the water is as good as any top of the line systems. But without a pressurized tank, you either go fetch water from under sink, or use a delivery pump. So a pump again, though at lower pressure the pump is cheaper, but not by a lot needing NSF testing. And you start to worry about the air quality, and air borne bacteria. Until the permeate pump, which is a lot cheaper without electricity and at lower pressure. Basically it's a weak hydraulic pump, pumping filtered water into the pressurized tank. With a pump, the pressure of the tank is isolated from the membrane. So the membrane is seeing the full water pressure all the time.

I'm going to describe safe materials and the correct design of an RO system. Indeed if there are not so many one man company selling put together systems, I may start selling too.

Thursday, August 16, 2007

Reliable precision vacation automatic dog feeder and waterer 2

With a little time, my feeder has improved a great deal. I found out by accident that corrugated cardboard box can be treated like wood. You can screw them, bolt them and nut them, glue them, tie them, and best of all, they comes in with most mail orders over the Internet.

Now the feeder is almost like my original simple vision. Find or make a box that is large enough to hold one meal. Use the side with the smallest dimension as the door. Drill two hold to mount the motor, using small bolts and nuts. My toy motor kit comes with a gear box that can mount a rotating arm. The arm is used to keep the door shut. When the motor rotates, the arm rotates away and opens the door for the dry food to drop down. You can drop down a tray of wet food too.

The rest you need is a 7 day timer to turn on the dc adaptor, which in turn drives the motor for a minute. For each day (or meal) you need three components, box with motor, dc adaptor and timer. They work independently so it's highly reliable. There's no single point of failure. And unlike commercial ones that uses a single "valve" to move the dog food, my design allows you to put whatever you want into the box precisely - medicine, treats for different days of the week.

I mount the boxes near the top of a large cardboard box, and tie the large box to garden furniture. There is no mess as the food will not drop outside of the large box, and the dog can't possibly move the box tied to something heavy.

There are plenty of automatic waterers, basically like the toilet tank that will automatically fill themselves and shut off when full. But the commercial ones are far too small, and far too expensive compared to the toilet flush valve.

I was looking to build something to mount a small float valve when I found something better. It was a float valve designed for cattle. I just mount it on a bucket with the supplied hardware and attach a garden hose to it. The large volume in the bucket acts as a large dead weight so I don't need to fix it to anything. Even if the water supply is cut off, the bucketful can last for days.

Now it may be getting even better and more interesting. I'm going to build a reliable circuit so I can get rid of the adapters and the timers. There will only be one power supply, which can be AC indoors, DC outdoors or battery operated. Before that it's a bit daunting to set up all the timers and adapters and boxes.

Nowadays it's amazing with the net. You get electronic components from 1 to 1 million over the Internet, and you are welcomed the same. And there's the online datasheets for you to design like a pro. There are free circuit design software for you to download so you will be biased to a supplier's components. Then some other free software will turn your design into state of the art circuit boards. It's a little expensive to make a single product. But if you make a few to give it to family and friends, the cost isn't that bad.

Inevitably, I can't rely on cardboard boxes. They have to be replaced all the time. Again thanks to the Internet, you can use any materials you desire, from carbon fiber to metals to plastics. You just draw your parts on a free CAD package, push a button, and the price will be quoted to you. For my case acrylic is suitable. I can cut and glue it myself or I can find laser machines to cut the pieces for me with high precision.

If I go through with these, someday I may get rid of the bucket and turn the automatic waterer into a sculptured acrylic fountain.

Monday, August 6, 2007

Vacation automatic dog feeder for large breeds

The background is that I have just two days to find an automatic feeder so I can escape for a few days. Feeders are too expensive or not good enough to be sold in stores, so you can return easily. I couldn't find one and couldn't wait for mail order, so I have to build one. I don't even have time to wait for mail order components. And since I have no time to test the feeder, it must be very reliable.

For the first draft I can think of timer and sprinkler valves. For off the shelf components, I have to use one timer per day to activate something. Water is a good counter weight to bring food down from somewhere. Tubes can be custom made easily. Now sprinkler timers have 7 day program and each has at least alternate day programs. So I can save half the number of timers. I wasn't expecting too much of a vacation, just a weekend get away or up to a week will be good enough. It turn out that one timer per two days isn't a reality and so many custom pipes become a nightmare.

Then came the thought of a toy car coming out from somewhere to bring the food. A car each day. But now cars all come with remote control, so I have to rip off the remote control to get to the electronics, which adds to another level of unreliability. And also, the battery saving features in the cars may do something unexpected.

Fry's save the day. Now instead of an Outpost website, they put their name on it. I found toy motors online and found it in their stores too. Motors are everywhere, but theirs are kits, complete with gears box and mounting screws. Surprisingly it's purely made in Japan, and I don't know how they justify the low tech manufacturing, though the plastic gears are rather precise.

At the end, it become something like this, for each day:
  • One AC 7 day timer - reliable and easy to program, you can't go wrong
  • One AC to DC adaptor - to get 3 V for battery operated motor. With the exchangeable plugs, the motor wires can be clipped to the plugs without soldering.
  • One motor with low gear ratio and mounted wheel.
  • One heavy plank wood beam 1" x 2" in cross section
  • A tray large enough for one portion of dog food
  • Sewing thread to pull the tray
  • A table in the yard
  • Optionally a large bowl to receive the dog food
The motor is mounted at the end of the wood beam, which overhangs on the table. When the motor is on, it will coil the sewing thread and pull the tray of food. The tray is initially at the edge of the table, next to the beam as a sliding guide. Pulled by the motor at the end of the overhanging beam, the tray will fall off the table, and the food will fall down onto the ground or a huge bowl. Food pellets will fall everywhere due to the inaccurate trajectory of the tray. So you need a huge bowl to receive it or let it fall on the ground. You can also wrap the dog food in a bag if the bag is eatable or the dog will not eat it, you get the idea.

The gear ratio has to be low enough that the motor is powerful enough to overcome friction, and powerful enough to pull the thread to breaking point after the dog food is delivered to the ground. Since the thread is attached to the wheel and to the tray, the string thread has to break or it will be chaos. The mounted wheel isn't important as long as the thread has something to tie to. The powerful motor will ensure that the thread will coil up somewhere and pull the tray along the beam.

The beauty of it is the reliability. If anything fails the dog just miss one meal. Unlike the other feeders, the dog will starve for a week and die.

I have been thinking of improving it so it can be used daily to save labor. However, you need something like a grain screw as in the commercial feeders. If I can find something like that, I can attach it to an electric drill, which could be rather reliable. Though the amount of dog food delivered will not be exact.

There are also other toy motor kids that allow you to build a conveyor belt for example. You might be able to build a single feeding machine instead of 7 machine if you leave for a week. For reliability, you can use two machines, one for the even and one for the odd days.

Thursday, July 19, 2007

VoIP earns you money!

I wanted to write on this topic before Sunrocket went down. But even as it is going down, it's still earning me money!

Ex-customers get special promotions. I get 6 months free if I rejoin my old phone company! So I'm earning money instead of just saving money. Same for satellite. If I switch back to cable TV, I'll get about $300 cash I guess, to pay for the satellite contract. But I have no contract! I'm tempted, but I'm just too lazy.

If I rejoin cable, I get $10 off since I had internet already. I get $5 off from satellite since I will have a proper phone line for their box. So it's not a pain to rejoin. But even with these discounts, I like the extensive features of VoIP, and I wouldn't switch back if Sunrocket is still in business.

Other VoIP companies offer to buy your Sunrocket contract, free adaptors, free phones, or port your adaptor to their service. Some have even more features like bridging your cell call to wireline calls.

The only regrets? My cordless phone become obsolete. I should have got just the adapter for free during promotions. Though the money I saved and earned should more than cover the cost of the subsidized cordless phones. But they are pretty good wireless intercom systems and wireless monitors!

BTW, I think what killed Sunrocket is the launch of T-mobile dual mode Wifi cell phones.

Thursday, June 28, 2007

VoIP killer applications

Home phone away from home
You can bring your "home" phone anywhere that has Internet connection! It's worthwhile to pack it with you - the phone is about palm size and the base sits on your palm. Sometimes it's important to give the impression of being at home, eg, taking sick leave to go on vacation! Or you can tell you friends that you are on vacation as it happens, rather than returning their calls after vacation. You can retrieve your voice mails with no extra cost anywhere in the world, rather than going through all of them when you come back.

But I won't bet on it 100%. There would be little difference within US. But Internet traffic between countries or regions may have bottlenecks affecting voice quality or reliability. But if you are on vacation, who cares.

It can't replace cell phones outdoors, but the charges are high for international roaming. For example, a US caller calling your US cell number can get through if you are in London, but someone has to pay for the international long distance charges. Usually people bring their GSM phone, or an extra GSM phone when they go abroad, then buy local prepaid SIM cards. So you have a number that your folks back home do not know, unless you tell them. They can still reach you, but international call charges apply. But for VoIP, there is no difference where your phone is, anywhere in the world.

Telemarketer killer

I can tell you that the no-call list don't work, only making telemarketer more aggressive. Dish network used offshore telemarketers to get around no call list? Firemen and policemen funds seem to be exempted. Debt collectors of course can call you until the end of time. Credit card affiliates can call you to sell credit protection plans and others.

Banging the phone and zippers don't work because the telemarketers are well prepared. It's part of the job and their life depends on it, scarifying the ear drum is not a big deal. It only make them more aggressive as if to revenge.

Having a landline is a liability. At worst, the marketing calls outnumbered useful calls 10 to 1 ! Most people use cell phone. I keep a landline mainly for international calls, and I don't use cell that much too.

Without caller ID subscription, it's suicide! CID alone doesn't do much. First of all, the phone still rings all the time. Second, you have to go up to the phone to see the ID. A CID announcing phone saves you some walk around.

Typically VoIP call features are inclusive, making it much cheaper than traditional phones. CID is always free. The other marketer killer features are call blocking. You can block all incoming calls without an ID, in this case you phone don't even ring! You can also block individual numbers. Call waiting ID allows you to see who's waiting before deciding to take the call.

Since most international calls do not have CID, I need a 2nd number with a distinctive ring tone for international callers. I also give this as a VIP number to friends and families. This number is free too. (You have only one number for outgoing calls, that is, your outgoing CID is your home number .)

After fighting with the telemarketers for a while, I know their tactics. First, they call with blocked ID's. Then they call with some misleading company CID, but you can recognize who's behind it after Googling it. If you block these numbers then they will have totally non-sense names or numbers like 12345678, or a combination of legit area codes and random numbers, like 602-00-0000. Then, the bad news, not a day after I heard on the news that they can spoof the CID, I got many calls from cell phone numbers that I don't recognize. Nobody left a message so I knew they are spoofing telemarketers. I don't take calls not on my electronic phone book. Then they give up.

Traveling service provider

If you ping pong between East and West coast for example, you will be using your cell phone for business, as most call plans are national in scope. VoIP is effectively a national plan, with the same charges no matter where you bring your phone, but cheaper. In addition, all US carriers do not support a second line (a second phone number) on a single phone. For VoIP, not only that you can have as many numbers as you like on a single line, you can pick any area code you want. This allows you to create the impression of local presence. It's either free or a few dollars for each additional number. However, your outgoing caller ID will always be your primary "home" number.

Traveling call center

Usually all your cell phone call log appears online in your account. I can't say that about landlines. But VoIP does it a lot better. First, extended CID means that you have a name on top of a number. Second, you can work your contact list online, rather than on your tiny cell phone. Third, you can listen to and organize voice mails online (though the voice quality is not as good as cell or your own recorder). With a laptop traveling, you can deal with a large number of new and old callers. With simple browser add-ons, you can, for example, highlight a phone number or numbers on your log, and lookup customer information from a database. Or you can lookup the database with a single click on a button, using the first X phone numbers on the log as the key. The call details appear pretty quick online, pretty much as quick as the demo on TV about how fast the credit card transitions will appear online.


It isn't relevant to VoIP technology but did I say I buy into VoIP because of the low cost equipment? I brought VoIP because I can have a decent cordless phone for cheap. Nowadays the intercom functions are pretty good. Press one button to initiate call and then scroll through the list to call the dining room, bedrooom 1 to 4, toilet 1 or 2, or everybody. It can hardly be simpler than a dedicated intercom.

Must have software for free email accounts

The open source Thunderbird email client is way better than Outlook, and way better than any company email clients in terms of user features. The non-trivial spam filter and message filters are certainly useful. I tried but didn't switched to Thunderbird as I do not have emails to use it on. To use it, your email accounts have to provide POP servers (for receiving) and SMTP servers (for sending). At least you need to forward your emails to an account that support POP. Free email accounts like Yahoo make sure you can't do any of that. You only get those features if you pay up in Yahoo, you get useful spam filters too. That's an awful lot of revenue for Yahoo.

The unthinkable happened. You can download and send emails from most popular free email accounts as if you paid up. Who doesn't have a few free email accounts? One for posting on Craigslist, one for registering for some free services, one personal, one for spams, etc. It's a pain to switch users in Yahoo, who punishes you by forcing you to read more advertisements. One account with multiple ID's is not safe. One day you will review the wrong ID to the wrong people.

Thunderbird has an extension called WebMail. After installing that and restart, you can install modules specific to each email service, including Yahoo, Gmail, Hotmail and many more.

Honestly this one escaped me for a while. For some reasons, it doesn't appear on the thunderbird recommended extension list, not on the popular list, nor you find it via casual search. Maybe the reason is just that the web pages are outdated. Perhaps the whole thing is understandably rather buggy in the first years. More likely, the email service providers can screw you up at any time to revenge their lost of business. Now after so many revisions of the software, I don't think they are going to do anything to sink it.

The installation is as easy as setting POP or SMTP accounts, as described in the instructions, though a little outdated. I would suggest first to setup the SMTP accounts first if possible, even if you don't intend to send emails via Thunderbird. Installation of POP accounts is as described, server is always localhost, and user is always user@domain - your full email address. Other details needed are display IDs that you can check later. What is missing from the instructions is that you need to go to add-ons, click on the email service module, eg Yahoo, and check the options. For Yahoo the default mode is the old version, most people would have switched to the new beta version, and that is the option that you have to set. It took me a while to get it working because of this.

In theory, Yahoo can screw you up anytime by changing their own protocol, eg from old version to beta. It's safe if you run Yahoo messenger and login to your most spammed accounts. If on a day that you don't seem to have new email notifications, there must be something wrong.

Webmail warned against setting up multiple SMTP accounts to send email. It didn't say whether it doesn't work at all or there will be some mixed up sometimes. I wouldn't do that anyway. I prefer login first to Yahoo to make sure that the account is the right one, before sending any email.