Analysis: piezoelectric air pump

[NiHaoMike]

Very recently, Big Clive did a video on a piezoelectric air pump:


I decided to get a 120V version for a simple project I wanted to play around with (atmospheric CO2 sensor) and I decided to open up the plug to analyze the circuit inside. The circuit is basically the same as for the 240V version:
* It has two 2k resistors in series instead of three 8.2k.
* The capacitor is the same but the inductor is 1.4mH.
* The silly 1M across the first resistor is there, along with another 1M across the pump.
* The pump itself measures about 63nF.

Not sure the exact purpose of the inductor. I was expecting it to form a resonant circuit with the pump but probing with a HVP70 probe across the inductor showed almost no voltage. Something interesting to note is that with the probe across the pump, the voltage slightly increases when the output is blocked.

[thm_w]

Probably a good pairing with a CO2 sensor to get a faster response and avoid dust buildup. Although if you don't care about response rate much, the air will circulate reasonably on its own.
If you use a PM sensor those will have fans so you can use that to blow near the CO2.

So it really is running at 60Hz? I had just assumed that is far too low for a piezo, at least optimally.
Maybe you can try a higher frequency as suggested in the comments (but wouldn't be at 120V).

[NiHaoMike]

It really does run at the mains frequency. I'm pretty sure the valves limit the maximum frequency it would work at.

[james_s]

Sounds a bit like those piezoelectric fans that were around for a while. I was always tempted to get one but they were relatively expensive and I couldn't really think of a good use for it.

[corkus]

Very interesting, thanks for posting!