Electronics > Beginners

Need help getting 2.4MHz piezo to oscillate at its resonate frequency

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MatCat:
His video was certainly interesting, but didn't help :)  The reason I am  even trying to build this circuit vs just use one of those drop in ones is that this needs to go in a water tank with pretty small dimensions and the tall height of the existing modules is too much as it will require the tank to basically be 1/3rd full for the atomizer to work, vs having the fiarly flat plug in disks that would allow it to be only a few mm.  Also a 555 isn't going to get to 2.4MHz.

MatCat:


Ok we are getting somewhere!  I built up the circuit you simulated only difference being I  used a 5.6nH for L1 since 5nH is not standard, I am getting 2 oscillations, a 205KHz and a 22MHz, not sure what I should tweak here, perhaps that 10uH should be 100uH?

MatCat:
I have a cheap DDS coming to me that can do up to the required freqiuences, I am going to experiment with this piezo and see what I can figure out.  What would be a good way to measure the resonate resistance?

T3sl4co1l:
Set up an impedance divider, the source (50 ohms) into the transducer.  Measure the gain, and phase if possible, of this network.  (Gain is easy enough, the output should be constant voltage and constant resistance, at all frequencies -- check this by sweeping the output with the generator unloaded, and with a 50 ohm load.  It should be flat, and the 50 ohm load should reduce its amplitude by half.)

Phase, you won't be able to measure the "top" of the impedance divider (because that's internal to the generator), but you probably have a trigger output to reference that.

Write down frequency, amplitude and phase in a spreadsheet.

Measure at least a reasonable density of points around the main intended resonance, but also sweep the whole range (say 10kHz to whatever max is, 10MHz say?) to see if there are other modes too.

Also repeat the measurements for different load conditions.

To convert that into a network, a rational approximation method is used to fit the curve.  This isn't trivial, but there is an algorithm to do it.  Then you can put the network into SPICE.

Tim

MatCat:
I found some data on the 2.4MHz 20mm  elements, capacitance of 1500pF +/- 20%, Resonate Resistance: < 3Ω, could you redo the values and simulation for this info?

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