The product is a wifi enabled smart switching device. One device has 4 different channel for four different appliances to be connected to the product. Each channel has a pair of optocoupler and triac for switching and dimming. The gate of the triacs are controlled by a microcontroller through a optocoupler.

The issue is misfiring of triacs. The circuit has a common line(220v) for all four triacs and whenever there is noise on any of the triacs, some of the other misfire for a fraction of second. As an example, if I connect a fan to one of the triacs, the fan being an inductive load, passes noise on the common line. Sometimes, one of the other triacs connected to LED lights misfire and a flash of light is seen on the LED lights. My assumption is that this is due to the power supply picking up even the smallest wave and converting it dc for the LED. This also happens if the fan, for example, also has a regulator in series. When the speed of the fan is changed on the regulator, for the brief split second for which the regulator knob is floating between steps, there are flashes of light on the LEDs. Sometimes these noises are so severe that the triacs are damaged.

How to remove this noise from the circuit?

  • 3
    \$\begingroup\$ What circuit? Where is it? \$\endgroup\$ – Andy aka Feb 13 '18 at 18:22

You need a snubber circuit to avoid these false turning on.

A second option (easier) is use a less sensitive triac. They called them "snuberless" triacs, actually. I had the same issue and changed from BTA600 to BTA600BW, and everything worked fine!

  • \$\begingroup\$ I did some reading and I think this will work. But as per my reading, what I understood was that if I put snubber across triac then the triac stays protected but chances are that the LED light will allow the snubber charge to drain and will give flash. If I put snubber across the load, then the LED won't flash but triac stays at risk due to transient noises. So what I was thinking was, what If i put a snubber across line and neutral, close to the triacs and their outputs??? That should solve for both cases, right? \$\endgroup\$ – Ujjwal Syal Feb 14 '18 at 10:35
  • \$\begingroup\$ So I ran the experiment. The snubber neighter works across triac, nor across line and neutral. Any ideas? \$\endgroup\$ – Ujjwal Syal Feb 17 '18 at 12:11

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