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Triac problems

Thread starter #1
I am having a problem with a triac BAT16, when I trigger it with an optocoulpler it turns on but the voltage is half of what it should be, Im trying to make a switch for 12 to 24 vac, I have tried a Q4006l triac but still have the same results
 

gophert

Well-Known Member
Most Helpful Member
#3
I am having a problem with a triac BAT16, when I trigger it with an optocoulpler it turns on but the voltage is half of what it should be, Im trying to make a switch for 12 to 24 vac, I have tried a Q4006l triac but still have the same results

Because a triac generally viewed as two SCRs placed head to tail. One SCR is triggered when the AC is positive and the other SCR is triggered when the AC current is in the negative half of the sine wave.

You are trying to trigger with an optocopuler (DC) and that can only trigger one of the two SCRs so you essentially create a half-wave rectified power and measure half of the voltage you expect.

In other words, you are only triggering in two of the four quadrants described in the Wikipedia article...

https://en.m.wikipedia.org/wiki/TRIAC
 
Thread starter #4
Here is the schematic, I figured it out last night I changed the 150 ohm resistor to 100 ohms works good now, thanks,
but I was wondering if I could trigger the gate with a transistor other than a optocoupler, or would it latch and just stay on
 

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crutschow

Well-Known Member
Most Helpful Member
#6
I was wondering if I could trigger the gate with a transistor other than a optocoupler, or would it latch and just stay on
You could, but you need the opto for isolation of the control signal from the 230Vac line voltage.
 

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