That would be a perfect case, but it would be harder and more expensive...
I think I just need to find the right fluid solenoids 
That's going to be tough with those solenoids. You are going to have to control the water pressure as well. You may find the solenoids can switch off faster with very low pressure. I'm thinking of a header tank only one or two meters above the solenoids. If some are on different levels to others, more header tanks.
It sounds a little like a big inkjet printer. They work with a pumping action - pulse a pump on and off to make a drop. You can probably get small 12V pumps that will be more controllable than solenoids. Then the input pressure is less important.
Is this more like a fountain? I've seen some amazing ones. Getting to that level of amazing requires some good mechanical engineering. Fortunately the Arduino is good enough to control that amount of amazing, with the suggestions above.
MorganS:
header tank only one or two meters above the solenoids.
The minimum operating pressure (according to the label) is 0.02MPa which is a little over 2m.
Hi,
The principle is the same as graphic fountains, but it's not to display 'water images', it's mor abstract and combines the graphic fountain principle, with a kinect and drop water to generate sound and trigger a projection... complex to explain but i think will be good.
Any example of an 12V pump ? Thanks
100 valves all at once will make quite a sound.
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like an orchestra, that's the point of this project...
You have two avenues which need exploration. Happily, up to a point, you can "divide to conquer"
- The water valves... you need to pin down lots of details. Do you really need to see 100 in action, right away? Get one (or a few) working first. Find out the things you don't know at the moment.... current draw, inductive spikes, etc.
Start this part with a simple mechanical switch that turns the valve "on" and "off". Progress from there to turning, say, three on or off with the outputs of an Arduino which also has three switches wired to three inputs. The "program" (sketch) would just, for now, be a very crude "if switch A closed, turn valve A on"
- Separately, at first, and while you are figuring out the details of driving the valves, start working towards how you are going to control 100 of them. There are many possible answers. The "right" one will depend on exactly what you want those valves doing. Initially, you can wire LEDs to the Arduino, to "stand in" for the valves that you will eventually be controlling.
If you are looking to do 1 or more "drops" perhaps looking into some sort of diaphragm pump would work better where you could pulse it once for each measured amount. They use something like that for the fountains you see that put out a stream of drops etc. (then they synch a strobe of some sort to the pulses to the pump for an interesting visual effect).
JimboZA:
The minimum operating pressure (according to the label) is 0.02MPa which is a little over 2m.
Last time I took one apart I saw a small plunger for opening/closing a very small hole, that filled a chamber with a bigger plunger. I guess some minimum pressure is needed for the bigger plunger.
Leo..
The larger "plunger" is a diaphragm. The practical working pressure is limited by its stiffness.
There is another concern - that small hole means that how fast the valve opens and closes is directly proportional to the water pressure. Low pressure = slow operation.
Paul__B:
The larger "plunger" is a diaphragm. The practical working pressure is limited by its stiffness.There is another concern - that small hole means that how fast the valve opens and closes is directly proportional to the water pressure. Low pressure = slow operation.
Yeah, our sprinkler system control valves have about a 5 second delay between power off and shut-off (on is fairly quick though). We have about 75psi in our lines here.
I wonder if your answer might not be a "little thingie" along these lines...
Take a medical syringe.
Where the needle would go, fit a 1-way valve... water "out", in the direction the syringe would push the meds.
Near the front, i.e. needle end, of the syringe barrel, cyinder, a water "feed", with a one way valve allowing water INTO the barrel, but not out, by that route. Connect that to a source of water, at neutral pressure.
To the syringe plunger, and electromechical whatsit to draw the plunger back, or thrust it forward.
Hope that makes sense.
tkbyd:
I wonder if your answer might not be a "little thingie" along these lines...Take a medical syringe.
Where the needle would go, fit a 1-way valve... water "out", in the direction the syringe would push the meds.
Near the front, i.e. needle end, of the syringe barrel, cyinder, a water "feed", with a one way valve allowing water INTO the barrel, but not out, by that route. Connect that to a source of water, at neutral pressure.To the syringe plunger, and electromechical whatsit to draw the plunger back, or thrust it forward.
Hope that makes sense.
Sounds like an inefficient diaphragm pump.
MorganS:
Sounds like an inefficient diaphragm pump.
It would have an extremely short life-span, too. Modern plastic syringes aren't intended for repeated use.
Short life: Yes!... I said "along lines"! (^_^)
I collect old books... recently added a "bible" for steam engine engineers, 1879. And also saw an old "toy" steam engine ("Mamod") recently. Probably had visions of pistons moving in cylinders in my head. Puff, puff, puff..... Squirt, squirt, squirt.
Not familiar with diaphram pump. Can anyone suggest supplier/ part number for one suited for posters wants? (YES, I DID a Google search... overwhelming!)
Maybe combine original idea with my idea.... sort of. Maintain a resevoir of water under a suitable pressure, and use a motor or solenoid to move a blocking piston back and forth in a cylinder, with briefly connected "entry" and "exit" ports for the pulse of water to squirt through? Yes! I do mean "a valve"... but am trying to suggest a form suitable to the poster's requirements, and one that gets around the problems (for him/her) of some of the commercially available ones.
Miniature dosing pumps could handle very small volumes and do what pssf wants, but the cost.....
If we are talking "medical", use a peristaltic pump. 
Hi all,
After a lot of research and your feedback (for what I'm very grateful), I decide do built my own solenoid.
It's gonna be a normal magnetic solenoid with a long stick and a rubber at the end. I'll have a water tank with holes that are gonna be closed with these solenoids in off state. When I turn them on, them will be magnetised and will come open and the water will fall from that hole...
This way I can open/close them very fast, and as the pressure is the same, if i open all and close ate same time they will fall always the same amount of water.
What do you think ?
thanks
What is the hole size?
What is the pressure?
What's the longest duration to keep the hole open?
How fast does the "valve" need to respond (time from closed to open and vice versa)?
I think an off the shelf valve would end up being the most reliable and feasible, providing it meets the conditions (answers to the questions above).
I've once done a project involving a bank of high power latching relays that needed a 12V/50A power source. Was able to use a 6A power source that charges a 1.5F super capacitor. The pulse needed for the relays was 150ms. If you only need to pulse the water on for short durations, then perhaps something similar could be done.
You learn about magnet solenoids in physics class at school but it's really only a theory. The amount of current required to get any reasonable force out of a linear solenoid is awkwardly big. The travel is also severely limited. That's why those solenoid valves get the water to do the real work and the solenoid is controlling a tiny orifice.
If all you need is actually tiny - a "drop" - then maybe this will work. I would be looking more towards motors and gears to open and close the droppers.