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How to drive piezo atomizer?

I am in need of some help as I attempt to improve my circuit design skills. I am trying to reverse engineer one of those aroma dispensers that use the little piezo-electric atomizers and a bottle of smelly oil. I have measured and characterized the signal at all the nodes on that circuit.

The trouble is they put that lame potted bare silicon die on the board so you have no idea what it's doing. I want to put on a little microcontroller or something and drive the atomizer for myself. The signal going into the power mosfet part is essentially a 3V square wave with maybe a 35% duty cycle. It comes out of the mosfet into a little transformer (which I am not understanding it's connections, but that may be another discussion), a big 3300uF cap and a 220uH inductor before going out to the atomizer.

There is a cap, a diode and another inductor but they all seem to be on the input side of the silicon part - possibly just for timing and blocking?

Anyway, if any of you kind and smart folks out there (does sucking up work in this group?) have any pointers for me I would very much appreciate it. It seems fairly simple, but I'm not able to completely recreate the final output signal. I have a function generator but I can't figure out how, or if it's possible, to set the duty cycle to something other than 50%. When I drive my circuit with the closest signal I can get, it doesn't get anywhere near the 150V (220v pk to pk) needed for the atomizer.

Many thanks in advance.

Reply to
aerelD
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Post a schematic somewhere so we can see the circuit.
Reply to
John Fields

The output impedance of your function generator might be limiting the rate of rise and fall on the signal at the MOSFET gate. Also, and more likely, the duty cycle is probably a very important part of the resonant circuit. Try using the generator output to drive the trigger input of an LMC555 (capable of operating at 3V) configured as a monostable (one shot). Use a potentiometer in series with a fixed resistor to allow you to tweak your duty cycle to duplicate the black box signal.

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Reverse engineering is, after all, engineering. You need to get crafty. You know what's coming out of the black box. Follow Mr. Fields' advice and muscle out the rest of the circuit. Get it down on paper. It helps.

By the way, if you post back, you might want to mention which function generator you're using (and whether you have a scope). Newsgroups can't read minds.

And Google is your friend. Try "piezoelectric atomizer" (no quotes) and explore.

Cheers Chris

Reply to
Chris

What frequency is your generator set at? The ceramics are usually pretty high Q, so you need to be close on frequency. I don't think you need anything other than a 50% duty cycle. Mike

Reply to
amdx

these are just scaled down from piezo humidifier designs. get a few of those schematics and like the other guys have said, as long as the ceramic is driven at the right freq (usually major mode, but often using harmonics) you can vibrate any liquid into scattered partiticles to drift off away into the air. i have used those cheapy peizo buzzers to perform this task with a little mod. most already have the circuits built into the case (and they are cheap)

us navy has done extensive research on ceramic transducers, they may have some design unique designs for incidental information also.

Reply to
HapticZ

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