PWM and resistor current

Archiver

[font=arial,helvetica]I want to power a piezo element with a stamp II using ·the pwm function and a
pnp Mosfet. The piezo uses up to 100 volts DC, and less then 100ma current. I
planned on filtering the pwm to supply a steady voltage. Probably a 10k
resistor and 100uf cap. how much current can different wattage resistors
handle? what if I didn't want to use real PWM with a hi current motor, what
would one do in that case? Any info would be appreciated.

Thanks[/font]

Archiver

>I want to power a piezo element with a stamp II using the pwm function and a
>pnp Mosfet. The piezo uses up to 100 volts DC, and less then 100ma current. I
>planned on filtering the pwm to supply a steady voltage. Probably a 10k
>resistor and 100uf cap. how much current can different wattage resistors
>handle? what if I didn't want to use real PWM with a hi current motor, what
>would one do in that case? Any info would be appreciated.

Dear electronguy,

There is a nice high voltage piezo element driver circuit in "The Art
of Electronics" in the chapter on fet's. They developed it to drive
the adaptive optics in the rubber mirror of a telescope.

wattage = volts^2/ohms


I highly recommend the book mentioned--it is a classic.

-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com