Input supply jerk of triac when power turned on

Thread Starter

abdullah8391

Joined Sep 6, 2015
92
Hi,
I implemented the circuit from this video. After implementing, I realized a mistake, whenever the main supply switch turns on, there is an initial jerk (also visible in the video, the link starts video video from that point of issue) then triac operates as per gate voltage level on gate. Is there any way to mitigate that initial jerk?
I used 68 pF capacitor in parallel to the gate resistor but it didn't work. I exactly can't narrow down the exact reason of initial jerk. Any help would be appreciated.
 

AlbertHall

Joined Jun 4, 2014
10,226
Probably the triac is being triggered by the rapid rise of voltage when the power is switched on (dv/dt triggering). To avoid this connect a snubber across MT1 and MT2. The snubber is a resistor in series with a capacitor. I would suggest values of 100Ω (carbon composition) and 100nF (it should be an X-rated capacitor. This means that it is suitable for permanent connection across the supply voltage).
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
92
I tried 100 ohm with 68pF capacitor and it didn't help.
Furthermore I narrowed down the issue, bulb connected with triac (no gate supply connected), there are jerks. Apart from that I used BTA16 and it didn't give any jerks. 12 watt LED bulb is used as load.
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
92
I want it to work with BT136, bit I can't comprehend the issue that is causing jerks.
I tried 100 ohm with 68pF capacitor and it didn't help.
Furthermore I narrowed down the issue, bulb connected with triac (no gate supply connected), there are jerks. Apart from that I used BTA16 and it didn't give any jerks. 12 watt LED bulb is used as load.
 

Audioguru again

Joined Oct 21, 2019
1,733
Another You Tube video from India with a dirty soldering iron!
It has the pot connected backwards, the light gets brighter when the pot is turned counter-clockwise.

I have an AC dimmer that I purchased. It does not blink the light when it is turned on. Its light gets brighter when its pot is turned clockwise.
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
92
Another You Tube video from India with a dirty soldering iron!
It has the pot connected backwards, the light gets brighter when the pot is turned counter-clockwise.

I have an AC dimmer that I purchased. It does not blink the light when it is turned on. Its light gets brighter when its pot is turned clockwise.
Can you share circuit or any more relevant details about it?
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
92
I tried 100 ohm with 68pF capacitor and it didn't help.
Furthermore I narrowed down the issue, bulb connected with triac (no gate supply connected), there are jerks. Apart from that I used BTA16 and it didn't give any jerks. 12 watt LED bulb is used as load.
Sorry I was wrong about BTA 16. After some testing it also showed same behavior.
At the moment I am studying about snubber circuits, will try to design and test it by tomorrow and will share the response details. In the meanwhile anyone has other suggestions, I will be happy to listen to them.
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
92
Google has hundreds of simple AC light dimmer circuits.
Ok.
But my main aim is to use triac as a switch (you may have noticed I have been talking about LED bulb). Since I didn't had proper recording tools and a video on dimmer representing my issue was available, that's why I started with dimmer.
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
92
Probably the triac is being triggered by the rapid rise of voltage when the power is switched on (dv/dt triggering). To avoid this connect a snubber across MT1 and MT2. The snubber is a resistor in series with a capacitor. I would suggest values of 100Ω (carbon composition) and 100nF (it should be an X-rated capacitor. This means that it is suitable for permanent connection across the supply voltage).
Thanks a lot mate. I tried to search for some theoretical designing of snubber but couldn't found any valid data, so after some hit and trial I found the right values. Again thank you for your time and help.
 
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