Homebrew PCBs

What you describe there is a simple membrane pump.
thousands sold each year (a lot of them for air pumping).
i tried it with a speaker @50hz, speaker diameter about 12cm.
the membrane hat to be sealed (used silicone).
with air id did make some suction (wanted it for vacuum-bag lamination).
but not very much, very low efficiency. (@50hz)
(membrane pp amplitude was 5mm  - then it smoked, stopped to move and i 
discarded it ;-))

i don't think this makes a good fluid pump, the liquid would drastically 
reduce the
maximum operating frequency/ resonance point, and the coil in standard 
woofers is for moving air
not 2 bar water or so....


the membrane pump is well known, well used, but i can't remember having one 
seen for liquid.

i'm still not sure if a perestaltic pump would be easy to make big, i have 
no hose
which can be compressed to zero gap and fills itself afterwards (only by 
gravity).
and also i think the stress put on any hose to compress it so much at the 
edges
is not good over time.

another possibility might be a bellow pump, same prinziple loke a piston 
pump
only the varying volume is accomplished by a rubber/plastic body which is 
compressed.
(in principle steves membrane pump is same but with a much larger 
amplitude, much lower frequency.)

st







On Wed, 01 Oct 2003 14:37:37 -0000, Steve <alienrelics@...> wrote:

> Using larger diameter silicone tubing means it isn't hard to fully
> collapse the tube for a peristaltic pump. And you always use 3 ball
> bearing rollers, can't just rub. A geared surplus DC motor or a
> stepping motor should work for this.
>
> To maintain pressure you could have a small reservoir tank. Sealed,
> with air inside. If you pump until it is half full, you've got 1
> atmosphere of pressure. You could even rig up a few photosensors to
> control the speed of the motor to regulate pressure.
>
> I was thinking of a pump idea for something else that may work here:
>
> Two one way valves (those little rubber ones you can get from a pet
> store for aquariums) rigged to a cavity. One wall of the cavity is a
> rubber membrane with a small woofer sealed to it. Not -quite-airtightso 
> barometric changes don't bottom out the woofer. Experiment with a
> signal generator and find the best pumping frequency when it is
> pumping fluid.
>
> No idea how scalable that is or if it would provide sufficient
> flow/pressure. Maybe the outlet oneway valve could be exposed and it
> would spray out of that with sufficient flow (I'm talking about the
> ones that look like a flattened baby bottle nipple).
>
> Since the woofer has a back, too, potentially you could make a
> doublesided pump. Otherwise all that energy just goes into making your
> workshop noisy. Then you could seal the woofer in completely as
> barometric changes would make no difference, and rely on slow
> diffusion through the cone to keep pressure equalized across the woofer.
>
> There, I just gave away a good idea I probably should have kept to
> myself and developed, and offered for sale. :'/
>
> Steve Greenfield
>
>
>
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