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Making a triac phase control circuit - are my values correct?

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floobydust:
Well, you seem to have the curse of the triac.

The whole circuit works on the premise that the triac turns on - if it doesn't, then the load gets power through the potentiometer/diac and it smokes.

Check the triac pinout you don't have MT1 and MT2 flipped, and that you are not using counterfeit triacs. There are many dud triacs out of china that are fakes. You could make a test circuit keeping the 70W light bulb and just a resistor from gate to MT2.

The only thing I could be wrong about is the delay/trigger cap is too small for low-sensitivity triacs and 0.1uF is better, but there is well over 50mA gate-trigger pulses from a 0.047uF at 32V. Check the diac should do nothing until around 32V when it turns on, if you have a shorted diac then there would be no gate current pulses.

Between MT1 and G you should read a diode junction I think, no resistance.

ExtraThiccBoi:

--- Quote from: floobydust on March 09, 2020, 08:20:24 pm ---Well, you seem to have the curse of the triac.

The whole circuit works on the premise that the triac turns on - if it doesn't, then the load gets power through the potentiometer/diac and it smokes.

Check the triac pinout you don't have MT1 and MT2 flipped, and that you are not using counterfeit triacs. There are many dud triacs out of china that are fakes. You could make a test circuit keeping the 70W light bulb and just a resistor from gate to MT2.

The only thing I could be wrong about is the delay/trigger cap is too small for low-sensitivity triacs and 0.1uF is better, but there is well over 50mA gate-trigger pulses from a 0.047uF at 32V. Check the diac should do nothing until around 32V when it turns on, if you have a shorted diac then there would be no gate current pulses.

Between MT1 and G you should read a diode junction I think, no resistance.

--- End quote ---
I thought MT1/MT2 can be flipped since the current runs both directions? Well anyways, I tried to do the math and me dumbass didn't take the resistance change after removing the 470k into account. This means the timing was kinda f'ed. I rebuilt it with the 470k, will check the mt1/mt2 and try tomorrow bulb test again. It's most likely not counterfeit. I buy my parts from a local store and never had an issue with fakes, they do look very real with all the respectable STM markings (both diacs and triacs are STM).

ExtraThiccBoi:

--- Quote from: floobydust on March 09, 2020, 08:20:24 pm ---Well, you seem to have the curse of the triac.

The whole circuit works on the premise that the triac turns on - if it doesn't, then the load gets power through the potentiometer/diac and it smokes.

Check the triac pinout you don't have MT1 and MT2 flipped, and that you are not using counterfeit triacs. There are many dud triacs out of china that are fakes. You could make a test circuit keeping the 70W light bulb and just a resistor from gate to MT2.

The only thing I could be wrong about is the delay/trigger cap is too small for low-sensitivity triacs and 0.1uF is better, but there is well over 50mA gate-trigger pulses from a 0.047uF at 32V. Check the diac should do nothing until around 32V when it turns on, if you have a shorted diac then there would be no gate current pulses.

Between MT1 and G you should read a diode junction I think, no resistance.

--- End quote ---
So yeah, the first triac is dead, coz i rewired the circuit and it didn't work. Ill build it with the second one. Hopefully it will work this time.

floobydust:
If nothing happens at 1/2 way on the potentiometer, don't crank it up until you find out what is wrong.

ExtraThiccBoi:
Learned the hard way :DD Yeah I always put it to max resistance before plugging it in.

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