Servo-controlled, two-way pneumatic pump?

[bzliu94]

Hi. I'm a high schooler from Oregon, and I'm in a bit of a dilemma right now.

What I'm trying to do is make a 5x5-pin tactile display for a high school physics project. I currently have a Makezine controller that can sink 1A @ 12VDC per analog output, and control 2 stepper motors or 8 servos at a time, for sure.

How I want the thing to work, though, is have its surface be bubble wrap for this first prototype, and I will empty or fill each bubble by opening or closing miniature valves attached to each, and then use just one master pump underneath to constantly oscillate, moving up and down to fill or empty cells that have open valves. Actually, now that I think about it, I'm probably going to have to use party balloons for the pins. And, here's a diagram:

http://img441.imageshack.us/img441/2707/crappyschematicnf6.png

Even though I'm dealing with air, though, I kind of get the feeling pneumatics won't be the solution I'm looking for as my displacement would be a dozen milliliters at most. Or is it still appropriate? I have almost no experience with pneumatics. Could someone please lend some insight? What part am I looking for, and does a servo-controlled pneumatic pump exist? Because for the vast majority of the time, the pump will be off, and it will only take an upstroke and downstroke whenever the screen needs refreshing.

Thanks,
Brian

Edit: And also, another reason why I want it to be something like servo-controlled is that I'd want to have variable amounts of displacement every cycle, depending on how many bubble on/off states are switching in that frame. The max displacement would only be going from all 25 bubbles completely off to on.

 

[brewnog]

I don't really understand what you're trying to do, but instead of pneumatics, how about a small hydraulic system?

Your pockets could be inflated by either:

- One pump and a series of servo valves to direct the flow accordingly, or;
- A master cylinder powered by a linear actuator for each pocket.

The second way might sound complicated, but it would allow the pockets to concurrently fill independently of one another, and would satisfy your need for variable displacement. The control system would also be much more simple.


The problems I see with your idea are as follows:
- I suspect you might need more than just good luck to evacuate the bubbles and cause them to empty, particularly if you use bubble wrap; think about when you pierce a bubble, it retains its shape.
- Control of air flow, though this could be done with a simple blow-off valve

Just some things to consider

 

[Danger]

What about a sealed system for each pocket? You could run a solenoid or motor driven hypodermic syringe (3cc or so) with a tube bonded to the underside of the pocket. Retracting the plunger would then also positively evacuate the bubble.

 

[wxrocks]

Do you have a size limitation for your display? I think that may help with some other ideas without limiting it to your bubble wrap idea.

 

[FredGarvin]

There are companys that produce valve/nozzle systems for manufacturing that are used in the application of very small amounts of a fluid. They are used in places like adhesive application top PCB's. Let me look around and see if I can find some links.

 

[bzliu94]

Thanks everyone for the replies. I'm extremely busy at the moment, but I will take the time to write out a reply ASAP. I think FredGarvin has the right idea..