Help needed: Issue on Triac switching 230V AC 700W vacuum cleaner

Thread Starter


Joined Dec 6, 2008

With internet help I made one Triac circuit to switch on my 230V AC portable vacuum cleaner.

It works with some issue. When switch on the socket power, though I have not given 5v power at MOC side, the load gets ON for about ½ second and turns off.


I’m using

BT136 600D , MOC3062 , 700 watts 230v AC vac.cleaner.

Once it turns off (after ½ second) I’m able to switch on or off via s1 at MOC side.

MOC3062 already has zero crossing. I already have the snubber with 0.1uF/600v(code 104) with 100 R 1W.

But I’m not getting why it doesn’t work.

Any chance that snubber part doesn’t work?
Or is it due to the capacitor [may exists] in vacuum cleaner?

Please help me, I greatly appreciate the help.

Thanks in advance.


Joined Jun 26, 2012
Switching 240V on with a mechanical switch generates lots of transients until the contacts settle down.

One possibility is getting switching noise into the the gate of the power triac and it is triggering. Usually, some kind of resistor between the gate and low terminal and/or capacitor filtering on the gate is present to prevent this.

You also might be getting dV/dT triggering of the opto triac (or the power triac if the snubber is not right or not working.)

Open the line between the opto and the triac and see if it still does it. Then proceed accordingly.
Its a wild guss, Keep a 1k between input pins of MOC3062 and try. Similar issue I face once we desined SS voltage stabilizer, We could not solve the issue and finaly went with relay

Thread Starter


Joined Dec 6, 2008
Hi thanks for the suggestion.

Opening the lines between the opto and gate has no effect. I added 1K 1W res between gate and T1 also doesn't sove the problem. I dono if this is because of snubbers caps 600v insted of 400v ?

I might have to try changing the snubber R C values (thanks for #12 on those pdf files)

as of now not solved.

once again thanks for all helping on this.

Thread Starter


Joined Dec 6, 2008
hi thanks for files.

but I'm not so good in electronics to understand this level.

anyway I'll try reading many times to get it.

thanks once again