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I’m developing a huge project, very cool but very complex, is a “water printer” based on the work of a Japanese artist. I’m an electrical engineer so I’m very good at electronics and software dev, so most of the project is already done, I made a computer controlled interface that can control several solenoid valves at the correct rates to “print” an image using water and gravity, here you can see an example of an early stage of my project simulating the valves with just LEDs.

I never worked before with solenoid valves, I bought some on ebay from Hong Kong, but I made I mistake, this kind of valve need a fixed amount of pressure to displace the actuator so they are very slow to close (not good for this project given the fact that I need a droplet), also I just find valves form 1/2’ (which are very big) and for about 10 bucks, taking in consideration that even if they work I will need about 100 of them, I can’t afford 1000 dollar for this.

I decided that the only way to solve this is building the valve, but I’m not very good imagining mechanical actuators, so I need the help of creative minds like yours guys. I’m just going to simplify what I want, imagine that you need to control the flow of water of an fish tank pipe using an electric signal, that’s it, what do you think? Let your imagination fly! :)

Nick Alexeev
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DomingoSL
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    If you can't afford even $10 for a small, fast, precise valve I doubt you will get anywhere with this unless you can come up with a very clever DIY solution. You cartainly won't find anything commercially available anywhere near that cost. Automotive fuel injectors might be worth a look for inspiration. – mikeselectricstuff Apr 14 '12 at 22:54
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    I think he's looking for exactly that, @mikeselectricstuff: a clever DIY solution. – tyblu Apr 14 '12 at 23:02
  • @tyblu hahahaha thanks for helping mike understand my point – DomingoSL Apr 14 '12 at 23:10
  • Evan a DIY solution will need some sort of actuator, which I doubt is possible at that price range without spending a lot on tooling or lucking out on something surplus. There have been a few displays like this, and it is likely some have patented their valve designs, so a patent search may be a useful way to find ideas, or at least get a feel for how hard it is. – mikeselectricstuff Apr 15 '12 at 09:36
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    Sounds more like a mechanical question.. – m.Alin Apr 15 '12 at 12:05
  • @m.Alin a good part is mechanical, but it has plenty of electronics problems – DomingoSL Apr 15 '12 at 13:40
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    Do you have a target price per valve? – Rocketmagnet Apr 15 '12 at 15:42
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    Um, this is definitely a mechanical question, as you yourself claimed the electronics aspect of the project is nearly done. – dext0rb May 21 '12 at 01:39
  • If you have searched this site then you would have found various solutions presented **[here](http://electronics.stackexchange.com/questions/4373/computer-controlled-water-valve/4407#4407)** 2 years ago. Possible duplicate. – avra May 21 '12 at 09:44
  • I think you want to search for a "direct acting" solenoid valve, versus a piloted valve. I saw something that said 5-10 ms operation times... you might have to play around with the pulse time. – George Herold Jan 07 '16 at 18:02

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A solenoid is certainly the cheapest and easiest thing you can make yourself. Plus, it's not difficult to direct the flow of the water this way. You don't even need to make a valve. All you need to do is to re-direct the flow of the water.

Since you have a flexible tube, you simply need to move the end of the tube between two positions. In one position it squirts the water down, and in the other position, it squirts the water into a drain.

DIY Water director

You can wind the solenoid coils yourself. Just cut lengths of steel rod, and wind coil wire (enamelled copper wire around them).

Push the end of your water tube into a short length of steel tube. The springyness of the water tube will hold it away from the solenoid, and allow water to flow into the drain (This is also the fail safe position. When the power fails, it will drain). When the solenoid is energised, it will attract the tube, and allow the water to flow down and be seen.

You may find that the flexible tube doesn't actually work well as a spring. In that case add a spring. Or, use a fairly long piece of thin steel tube instead of the flexible tube. This will be flexible enough to move the approx 4mm required.

Rocketmagnet
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    Steel parts, water all over the place - what could possibly go wrong...! – mikeselectricstuff Apr 19 '12 at 22:01
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    Mike you really aren't much help, please try to be more constructive. I think the way Rocket has redefined the objective from stopping flow to diverting flow is brilliant. I have been trying to find a cheap solenoid valve for the same project and nothing under $20 came up. I may look into diverting flow this way using an array of electromagnets to move the tubes in and out of the drain gutter. Thanks for thinking outside the box rocket! – thomallen Apr 23 '12 at 04:01
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A solenoid and an actuator can be found in every mechanical relay made. You can find all manner of relays on the surplus market dirt cheap (read: < $1.00).

Now if you can find a way to couple a simple valve mechanism to the relay contact, there's your solenoid valve.

A very simple valve can be made from a pinched tube. In order for this to work with the small amount of force from a relay solenoid, the tubing has to be very pliable (think balloon material). The only problem is that it will not resist much pressure.

You could also make a simple gate valve, but I assume that since you're asking the question you don't have the tools to make anything with a close sliding fit that has low friction.

lyndon
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Also Piezo actuators are cheap too, fast enough, and strong enough.

Maybe usefull for categorizing some ways to control water flow:

  1. stopping flow
  2. diverting flow
  3. increase pressure in chamber and create droplets 3A by making steam (as in inkjet printers) 3B change volume of chamber by mechanical actuator (for example piezo disc chamber)
  4. much more possible
user96382
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enter image description here

literally my first idea for a easily, cheaply, mass produced solanoid with detailed fluid control.

enter image description here

and my first idea for a motor controlled dropper.

Wade Terral
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In addition to the ideas suggested thus far, I would suggest considering the possibility of modulating pumps. I don't really know how much water you need to control, but using separately-controlled pump for each spout may be better than having a master pump and using valves for each spout. Most pumps have a certain amount of mechanical inertia, but it may be possible to minimize such effect with careful electronic control. I don't know whether an IR compensated control will be necessary, or whether the mechanical behavior of the water would be predictable enough to be modeled and predicted in software. Modulating the motor between positive and negative voltage at a frequency high enough to exploit motor inductance, however, is an excellent means of controlling speed while providing regenerative braking (which could be useful, if nothing else, as a means of giving the pump's kinetic energy someplace to go).

supercat
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It is easy to find small valve, I am sure 1/4 direct acting solenoid valve will be cheap and fast, less than 3.00 USD per piece, you can find it in China website. they are a lot of types.

Mac Chang
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