Driving a piezo loudly!

I tried the circuit with no luck

You tried a different circuit, which won't work for several reasons.

You could try the one in reply #22, carefully following the instructions to replace the speaker (8 Ohm R2) with the piezo, but it won't be any louder than the direct output from an Arduino, because there is no voltage boost.

jremington - you're right of course.

1/ modelling a piezo as a series capacitor and resistor isn't very accurate , but it's a reasonable starting approximation. A better model will not be linear, but will vary strongly with excitation voltage. Can't be bothered.

2/ my crude circuit does not, as you say, provide any voltage gain, but it will provide much more current, which may be useful driving a low impedance series resonant load.The series l-c provides the voltage gain at resonance.

Pwillard : your circuit is a basic boost voltage convertor - but we don't want high voltage dc.

Danielvt. Your implementation of my circuit is inaccurate. Get it right and try again.

1 resistor, two transistors. Omit the 100uF capacitor. Could anything be much easier?

Allan

Didn't read all the posts in this thread, but isn't it easier to use a MAX232 to drive a piezo. Like the do on an HC-SR4 ultrasonic sensor module. The MAX232 should be able to drive a piezo to ~30volt peak/peak. Leo..

Wawa: Didn't read all the posts in this thread, but isn't it easier to use a MAX232 to drive a piezo. Like the do on an HC-SR4 ultrasonic sensor module. The MAX232 should be able to drive a piezo to ~30volt peak/peak. Leo..

Hi Leo!, thanks! I can't find any resources on how to wire/set up the Max232 to a piezo, could you elaborate? I believe 30vPP from a 3.3v source sounds amazing though! :-)

/ Daniel

Google "HC-SR4 schematic diagram" (images). The first diagram shows how to connect the MAX232. Not sure about powering this chip with 3.3volt though. Consult the datasheet. Leo..

The MAX232 psu generates +/-7v with a 7k load, only +5/-4 v with a !k load. It requires a +5v supply.

If you just want to to the job with a high voltage supply a boost convertor would be OK - but you then also need a suitable circuit to drive the piezo.

The op has already achieved 17vac from a 3v5 signal using a series resonant circuit. Since the waveform will be sine-ish that implies 48v p-p.

Allan

Danielvt: we're running on a 3v battery - which is why i'm using a LC-circuit :)

This one is loud, 4.5V, for high voltage they are using autotransformer,

http://makercorner.blogspot.com/2017/06/diy-refrigerator-door-alarm.html