[sdiy] pneumatic oscillator

[Batz Goodfortune]

Y-ellow Jim 'n' all.
         I was a bit afraid to elucidate but if I must.

I was looking at the slide cariage that drives the head on a CD drive. 
Pretty simple in effect. A geared down worm drive. So in essence, you could 
have a worm drive that locks through the plug from the bottom. Turn the 
worm, the plug moves.

You could use a stepper or a servo. I went for a servo because that's what 
they use on the CD drives and it's more directly voltage controlled. But 
whatever turns you on. You already have a feedback mechanism of sorts. Just 
measure the frequency of the output.

But I just thought of another way. You're already playing with gas. Air in 
this case. So why not have the plug pneumatically coupled? Say an air-bag 
or piston at each end. Whatever drives it can then be mounted away from 
tube it self so that motor noise isn't coupled to it.

You could probably do it equally well with hydraulics. IE: A pair of large 
syringes connected nose-to-nose through a tube. Move one and the other 
moves in sympathy. Which is what I have for you if you should even try this. :)

In hospital, when they were pumping me full of industrial strength pain 
killers, I was fascinated by the machine they used. An automatic syringe 
pumping gizmo. It's essentially a gripper that fits a fairly standard 
syringe and driven by a worm screw. You hit the button and it hunkers down 
on the flanges of the syringe. Pumping a few more CCs of happy juice into 
your veins. Of course the back-pressure of a syringe is probably too much 
to expect a small servo or stepper to drive with any speed but perhaps 
something along those lines.

What about making something like one of those slug-solenoids. In effect a 
voice-coil linear motor. Wind the coil round the outside of the tube it 
self and have a magnetic plug. Probably spring loaded at each end or 
something. This is probably the best way if you want to keep it analog. 
Otherwise, tuning it for 1 volt/oct is going to be a real bitch. :)

Or perhaps instead of a slide whistle type arrangement, how about a varying 
aperture of some kind?

Ok. So this leaves no doubt that I'm completely insane but then again, I'm 
not the one having to build the thing. :) That being the case I just have 
to ask. What have you got planned for a VCF?

Be absolutely Icebox.

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