Why my lamp doesn't light up with my TRIAC? (See picture)

Thread Starter

Giuseppino Brandini

Joined Jun 20, 2021
5
So I'm using a TRIAC that is supposed to be activated through 3.3v from my ESP8266. But it's not happening.
problem circuit.png
I've measured everything with a multimeter and the problem is that the TRIAC isn't being activated and there's no passage between it's legs (A1 and A2). But I don't know why it's not being activated since its current gate is 35mA and Im placing 3.3/90 through it
 

LesJones

Joined Jan 8, 2017
3,570
You have no return path for the gate drive to the triac so there is no gate current to trigger the triac. This is a very dangerous way to drive the triac as the ESP8266 will be at mains potential. You should drive it using an optically isolated triac.

Les.
 

Thread Starter

Giuseppino Brandini

Joined Jun 20, 2021
5
You have no return path for the gate drive to the triac so there is no gate current to trigger the triac. This is a very dangerous way to drive the triac as the ESP8266 will be at mains potential. You should drive it using an optically isolated triac.

Les.
What if I put a ground connector from one of the TRIAC's legs, A1 or A2 to the ground of the adaptor?
 

Ian0

Joined Aug 7, 2020
3,752
What if I put a ground connector from one of the TRIAC's legs, A1 or A2 to the ground of the adaptor?
If it were still connected to the mains, it would trip your residual current circuit breaker.

Further notes:
1. Will the output pin really drive 35mA? Most microcontroller pins are limited to about 5mA
2. The triac requires a NEGATIVE current into the gate to trigger in all four quadrants.
 

Ramussons

Joined May 3, 2013
1,098
So I'm using a TRIAC that is supposed to be activated through 3.3v from my ESP8266. But it's not happening.
View attachment 241765
I've measured everything with a multimeter and the problem is that the TRIAC isn't being activated and there's no passage between it's legs (A1 and A2). But I don't know why it's not being activated since its current gate is 35mA and Im placing 3.3/90 through it
A very dangerous way to interface the ESP to a live Triac. Besides getting accidentally electrocuted, you may also burn out the ESP.
Use an Opto Isolater as suggested.
 
respectfully, your original ckt, as well as being dangerous, shows no thought as to how the gnd of the arduino is referenced to the triac you think you can drive that way, either use an opto to safely isolate the arduino, or have everything referenced to the neutral, which is then the 0v for the arduino -- but don't touch it, and evn then a high voltage xtor will still be needed as the arduino o/p pin simply cannot do what you want, it has no resistance to sources higher than 5v dc, and 3, an isolating gate drive transformer with at least 1kV isolation rating .....
 

Ian0

Joined Aug 7, 2020
3,752
respectfully, your original ckt, as well as being dangerous, shows no thought as to how the gnd of the arduino is referenced to the triac you think you can drive that way, either use an opto to safely isolate the arduino, or have everything referenced to the neutral, which is then the 0v for the arduino -- but don't touch it, and evn then a high voltage xtor will still be needed as the arduino o/p pin simply cannot do what you want, it has no resistance to sources higher than 5v dc, and 3, an isolating gate drive transformer with at least 1kV isolation rating .....
If you do connect your arduino directly to the mains, making it's 0V reference mains live, then think about what may be connected to the arduino inputs. They will then also be mains live.
 
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