light dimmer using triac-bt151

Sensacell

Joined Jun 19, 2012
2,544
You need something to control the triggering of the triac to effect dimming.
Triac dimmers operating on AC use phase control to adjust the power delivered to the load,
that's what the diac does in the circuit, along with the RC network.

So no, it won't work without a diac.
 

Dodgydave

Joined Jun 22, 2012
8,683
A diac is just two 30V zener diodes back to back, it ensures that the capacitor charges upto approx 27V then it fires the triac.
 

Lestraveled

Joined May 19, 2014
1,946
A diac is just two 30V zener diodes back to back, it ensures that the capacitor charges upto approx 27V then it fires the triac.
This is an incorrect statement. While it is true they both will not conduct until a breakdown voltage is reached, this is where the similarities end. A zener diode will stay at the breakdown voltage, the Diacs voltage will drop. It kind of acts like a spark plug.

https://en.wikipedia.org/wiki/DIAC
 

Dodgydave

Joined Jun 22, 2012
8,683
In the past i made i dimmer using two zeners and it worked just as well, its better to use it with the diac as its designed for that purpose.
 
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