Triac Problem

[Abdullah Badarneh]

Hi,
I'm tired of trying search about this problem, and I didn't find any topic help me,
I made a circuit as in this image with keeping terminal 3 disconnected,

https://www.dropbox.com/s/xoxt8i2sheqcty0/Triac Problem.png

the problem is the lamp is flickering once I put/remove the plug in/from the power socket, as in this video

https://www.dropbox.com/s/xahbzf2li6c5su0/Triac Problem.mp4

I tried with two another triac bt136&bt138, but the same problem occured, any one can help me?

Thank you in advance.

 

[(*steve*)]

Is that an LED bulb? What happens if you use a regular filament bulb?

What are you trying to do? Do you intend to connect something to the gate later on?

Is there anything connected to the gate now? Even just a wire that's not connected to anything else?

 

[Abdullah Badarneh]

Is that an LED bulb? What happens if you use a regular filament bulb?

I don't know,but I think it's filament bulb, I will be sure when I back to home, thank you for this note.

What are you trying to do? Do you intend to connect something to the gate later on?

I tried to to control AC by connecting the triac with arduino using moc3021, but the problem occurs whether I connect the triac with moc3021 or disconnect it.

Is there anything connected to the gate now? Even just a wire that's not connected to anything else?

no, it's not connected with anything

 

[(*steve*)]

I suspect it's a LED bulb and that leakage through the TRIAC charges up a capacitor in the bulb until it turns on briefly before repeating again and again.

You probably can't use a TRIAC to dim a LED bulb (especially if it's behaving how I suggest above).

 

[Abdullah Badarneh]

I suspect it's a LED bulb and that leakage through the TRIAC charges up a capacitor in the bulb until it turns on briefly before repeating again and again.

You probably can't use a TRIAC to dim a LED bulb (especially if it's behaving how I suggest above).

the trigger occurs regardless the type of device, I tried to connect Samsung charger that connected to phone, the same problem occurred

 

[(*steve*)]

A Samsung charger is likely to be a switch mode device, and as such it may be very similar to a LED bulb.

At this point we haven't established whether the problem is due to leakage or false triggering of the TRIAC.

I have checked and these TRIACs are sensitive gate devices, so false triggering is a higher probability.

Assuming it is false triggering, a snubber across the TRIAC (a resistor in series with a capacitor across the MT1 and MT2 terminals) should help stop dv/dt triggering. However this will also increase leakage which may increase the problems for LED bulbs. Of the top of my head, a 47Ω resistor in series with a 0.1μF cap may be ok. Ensure the capacitor is mains rated.

A resistor between the gate and MT1 may reduce false triggering caused by any signals being coupled to the gate. Try a 4k7 resistor.

 

[Bluejets]

Floating pins usually cause many problems.

 

[Harald Kapp]

Floating pins usually cause many problems.

A 10 kΩ resistor from gate (in 3) to A1 (pin 1) should remedy that point.
The correct setup for using an MOC3021 with a triac is shown e.g. here.