SSREZ with PWM - Does it work?

Muskogee Gene

Muskogee Gene

New member
I'm playing with alternatives to PIC dimmers and thought PWM using the TLC5940 might be the ticket. I set it up on an Arduino and it doesn't dim. It flashes great but won't dim. Is there a reason that PWM won't work? It seems to be that it is simply a different way for the duty cycle to be changed - just as a PIC dimmer program would. What am I missing?

Gene
 
It sounds like you are missing a zero-cross signal to sync up your dimming to the EZ. The controllers that are used for the EZ typically have a H11AA1 chip on them to provide a zero-cross detection signal to the PIC. You need to have this to dim AC properly.
 
if I setup the Arduino to light LEDs on the breadboard, they dim great from the TLC5940. But when I attempt to send that signal to the SSR, it doesn't seem to work. I'm not sure how the TLC5940 does it but it doesn't have a port for zero-cross detection and it seems to work fine directly attached to LEDs. I thought the EZ didn't use zero-crossing components so it wouldn't be affected by zero-crossing and relied on the timing of the signals. Perhaps I am confused...quite likely.
 
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After thinking about it more, I understand what you were trying to tell me. It works with the LEDs because that is basically DC but there is no synchronization with the AC to switch at the right time. Got it. Thanks so much.

So bottom line seems to be that PWM chips like the TLCs won't dim A/C without help. Now all I have to do is figure how to help.

Gene.
 
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Muskogee Gene said:
After thinking about it more, I understand what you were trying to tell me. It works with the LEDs because that is basically DC but there is no synchronization with the AC to switch at the right time. Got it. Thanks so much.

Gene.
Click to expand...

Exactly right- the DC stuff does not require any sync but the AC stuff does to the house mains AC cycle - if you arbitrarily run PWM without sync you might get insanely lucky and happen to match the AC from time to time but generally it will look terrible. The H11AA1 chip is a cheap/simple circuit to use that you can run into your Arduino for sync. I think there are a few folks that have already been here so do some searching in the forum.
 
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