Triac Triggering

[mkh]

hi... What happens if i give a constant dc voltage , say 5 V to the gate of a triac when it is connected across line supply? say if i increase this voltage to 10V , is it that the triac will start conducting only after the supply waveform also reaches 10V?

 

[Hero999]

A TRIAC will turn on when the gate voltage rises by 0.6V above or below MT1.

Also the gate current needs to be limited to prevent the device from being damaged.

So your TRIAC will just turn on if you put 5V on the gate and it will stay on until the current through it drops below the holding current.

 

[Bob Scott]

hi... What happens if i give a constant dc voltage , say 5 V to the gate of a triac when it is connected across line supply? say if i increase this voltage to 10V , is it that the triac will start conducting only after the supply waveform also reaches 10V?

If 5V is applied to the gate of a triac, it will damage the gate junction. It's like trying to applying 5V forward voltage to a diode. The diode will conduct, the current becomes infinite and the junction instantly blows. In order to prevent this failure, you must use a current limiting device in series, like a resistor.

Check the data sheet of the triac in question for triggering polarity etc. IIRC, some triacs trigger in more quadrants than others.

Bob

 

[audioguru]

He blows up triacs with unlimited current. Does he also blow up other semiconductors like transistors and LEDs?

 

[mkh]

He blows up triacs with unlimited current. Does he also blow up other semiconductors like transistors and LEDs?

It was a theoretical question... i have not built any circuit with a triac... But i have blown up a couple of transistors

 

[Papabravo]

It was a theoretical question... i have not built any circuit with a triac... But i have blown up a couple of transistors

Hmmm...do you suppose that there might be new physics being discovered on the subcontinent?

 

[Bob Scott]

He blows up triacs with unlimited current. Does he also blow up other semiconductors like transistors and LEDs?

I wouldn't know. I just know that if I attach the probes of a DMM across a single juction rectifier diode and, with a source of 5V, I am successful at applying a forward bias voltage of 5V on the diode's anode with respect to the cathode, the diode is porked.

You can use a similar method to test fuses. Using clip leads, connect the suspect fuse in series with a 12V automotive battery. If you see a flash, you know the fuse was good.

Bob

 

[mkh]

Hmmm...do you suppose that there might be new physics being discovered on the subcontinent?

http://www.hinduwisdom.info/articles_hinduism/146.htm
http://www.blonnet.com/2007/02/23/stories/2007022303310400.htm
http://en.wikipedia.org/wiki/Science_and_technology_in_ancient_India
https://www.electro-tech-online.com/custompdfs/2007/06/cons.pdf
**broken link removed**
http://arxiv.org/ftp/arxiv/papers/0705/0705.1192.pdf