Remote Mains PWM

[Jerson]

what kind of distance are we talking of between the driver and the triac? Are you seeing ground loop issues? False firing?

[The Master]

The controller and all of the lights are plugged into various sockets in the same room (its my kitchen so not very big).

I dont think there should be any ground loop issues. I use opto isolators with each triac. The controller outputs about 5V into a wire that is about 3M long. That wire connectes through a diode and a resistor to the opto which then controls the triac.

I dont get any false firing. When the controller says the lights are off then they stay off. If it turns them completely on then they stay on. I only see the problem when PWM is enabled. I even tried programming the PIC to set the state of the outputs to match the zero crossing and put the code in a tight loop. In this case i would expect all of the lights to be permenantly on (maybe very slightly dimmed) but they still flicker or dont turn on at all.

Each output also has an LED. The LEDs are powered from the same transformer as the PIC and they appear to fade correctly

[Jerson]

Can you put up a small sketch of what your setup looks like? It's a little hard to figure it out in text.

[The Master]

Ive attached a basic diagram of the circuit. Everything on the left side of the line is the controller and everything on the right represents the seperate lights being controlled. The triacs are inside the light holders themselves. I have shown seperate AC inputs where things are plugged into seperate mains sockets. All of the mains sockets are in the same room on the same ringmain and are seperated by only a few metres of wire.

Note: I dont have the symbol for a triac in this software so pretend the MOSFETs are triacs.

[Jerson]

I would remove the diodes from the inputs of the optos. Reason : when you turn off the drive to the opto from the pic, the input of the opto is now able to take in mains pickup due to the long wire run. This will cause it to trigger falsely. Give it a try. No diode.

Other than that, I see no reason why your circuit will not work. I hope I'm not wrong

Regards

[The Master]

Im not having any trouble with false firing. This is the first time ive used the diodes in this kind of circuit. They are there to protect the optos incase the wires are connected incorrectly.

If you cant see any other problems with it then ill assume i have a short or dry joint somewhere or the program isnt right. Ill have a look at them in a lot more detail. Thanks for your help.

[Jerson]

You're welcome. Keep us posted with your results.

[ardhuru]

They are there to protect the optos incase the wires are connected incorrectly.

With a 1K resistor in series with the pic output, I dont think you would damage the opto LED even if connected reverse. I'm not saying removing the diodes is a solution, just that I think they are redundant.

Anand