Quote:
Originally Posted by rcheshire
You'll be pleased to know that I am not going to run the dew heater with PWM. I've taken your advice on that one - too noisy for this setup.
|
You can run dew heaters on PWM with minimal noise.
Thanks to the thermal mass of the mirror's and lenses we use, you can make a start in the right direction by using a very long period, say a few seconds. That brings the frequency a long way down out of harms way. The only real problem* then would be the harmonics produced by switching the strap on and off, which you should be able to attenuate with an RC low-pass filter.
(*probably not a very big concern, considering the very low fundamental frequency and the voltage used)
The resistance you already have(dew strap) so selecting a suitably sized capacitor, you should be able to get a sensible time constant.