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May 08, 2019, 01:09 PM
Go small or go home
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Fun with Piezos

I stumbled across this today. It shoudn't have come as a surprise, but this is the first I've seen.

The particular devices used on the blimp in the video appear to be microblower pumps made by muRata ( I base that conclusion on other links I've found for a DIY kit that includes a circuit board to drive the pump from a 3V source. FAIK this pump design contains no physical valves and relies on the air flow inlet/outlet design to force air in a particular direction. That of course makes it simpler and lighter (maybe even more efficient?). It does have a relatively high flow rate at a modest pressure.

Other piezo pump designs I've seen are more traditional in that they have one way valves on the in/out to force air flow in one direction. One way valves have always been the weak link in vibrator type air pumps. They clog and wear and quickly become ineffective. You can buy piezo aquarium air pumps (I bought one to rip apart). Same principle. A large piezo disk vibrates like a diaphragm to move air. It's much lighter, smaller and quieter than a traditional aquarium air pump. It also has specially moulded rubber one way valves.

In theory (and probably already tried somewhere?) you could use additional piezo disks as a control valves. Using the same drive frequency in a slightly different phase to open and close the input/output while the main pumping diaphragm works at expanding and compressing.

I believe DIY peizo air pump and control circuit could be manufactured weight mere grams. I've been stocking up on parts and thinking out some ideas of my own for micro pumps that could be used for ballonets. My idea is to use a two ballonet system where one ballonet is a solidly built foil bag that has been tested to hold as much pressure as possible. This ballonet would be a helium 'storage tank' completely contained inside the blimp, along with the piezo pump. On filling the blimp, this ballonet would be pumped internally until it was filled but zero pressure. It doesn't matter (much) if it leaks helium, as it will all be contained within the blimp. Then the ballonet would be pressurized by the peizo pump to maximum pressure, which would reduce the lift of the blimp. A second ballonet 'fill tank' with a second pump (also inside the blimp) would be connected to atmosphere. As the 'storage tank' is pressurized, the 'fill tank' would be inflated to maintain the blimp overall internal pressure. By managing the 'storage tank' and 'fill tank' pumps, with the help of some sensitive pressure sensors and micro valves, you should be able to dynamically control the blimp altitude. At least, that's the idea. Whether it can all be put together in a package light enough for an indoor micro blimp is a question I'm still working out.
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May 08, 2019, 05:47 PM
Melbourne, Australia
If you can crack buoyancy control for small blimp models that would be awesome!!

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