Dimmer switch

[iugmoh]

I want to ask if it's possible to replace the analog poteniometer of dimmer switch with digtial poteniometer to control the resistance of digital poteniometer using PIC so control the lighting or speed digitally ?

[Melanie]

Problem 1. The voltages across most Analog Dimmer Potentiometers would probably exceed the maximum ratings of a Digital Pot.

Problem 2. Most Analog Pot Dimmers don't have the Pot isolated from the supply mains. So you will potentially be wiring your Digital circuitry to an unisolated supply.

It'd be a lot easier to take a PIC and design a Dimmer from scratch, than try to cobble two alien circuits together. If you are going to go down the route of your original idea, a good knowledge of your intended Analog Pot Dimmer is a MUST - many will not be suitable, and some could even put the Users safety at risk.

[iugmoh]

Thanks Melanie for your information, I think my idea will not be suitable for my project, so when I try the dimmer switch with its analog potentiometer with my DC motor, then there are aloudy buzzing sound from the transformer when I decrease the speed or voltage.

But I want to ask :
is't important to add the flyback diode across motor terminals beacuse I add many diodes and everytime they damaged and damegd my mosfets. ?

[Melanie]

OK... you've lost me somewhere along this thread...

I assumed you had an Analog rotary Pot on a DIMMER and were replacing the pot with a Digital Pot (which is basically an IC) controlled by a PIC...

A DIMMER is good for (certain kinds of) lighting... DIMMER assumes LIGHTING. We don't DIM the SPEED of a Motor!!!!!!!!!!! Once you slow a Motor down (and there are many different kinds of Motors - all of which we handle differently), the current rises drastically.

[iugmoh]

oky so it's not preferable to use dimmer with DC motor control speed. Do you have any site or link which control speed of large dc motor ( 200VDC,300W,3A) , beacause I searched alot in google and can't find a good one which can help me to control my dc motor all I found is to control small dc motor.