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triac circiut not working

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subzero349

New Member
Sebi has posted the circuit I am using in the projects folder

I am trying to get a triac and optocoupler to turn on a light bulb (120Vac) when a bit from a microcontoller goes low...

If I put a capacitor across MT2 and MT1 the light is ALWAYS ON no matter what the microcontroller is...

If I don't put a cap across MT2 and MT1 the light is ALWAYS OFF not matter what the microctonroller is....

Any suggestions?
Any recommendations for triacs that are for 120Vac approx 8amps?

Please help! I've seen a lot of circuits that are all the same as Sebi's and they are supposed to work... but mine is not!!!
 

Sebi

Active Member
Ahhhh... neon lamp! (glimm) it have very small current consumption! Can work via serial condenser. Try the circuit with a small bulb (min.5..10W) The 0.5ma of glimmlamp not enough for TRIAC proper work.
 

subzero349

New Member
Thanks to Sebi for the help...
I am now using a 100W light bulb and the circuit works!

Sebi gave me the following circuit to work with (keep in mind not all triacs have the same pinout)

 

Sebi

Active Member
And here is a circuit for strong inductive loads. It work for me to switching 3phase motors also properly.
Thanks, Mosfet here is the pic
 

subzero349

New Member
Thanks, here's another question:

I'm using a PIC 16c715 for the logic to turn the opto/triac off and on.

The only port pin I have available is OPEN COLLECTOR (the board I am using also has a 4k7 pull up resistor).

I have not been able to get the Triac circuit to work with this OPEN COLLECTOR. Although when I measure the o/p with a probe I can get it to change from high to low...

Should I consider sourcing the current instead?
 
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