Friends have a simple circuit a switch on off using triac BTA24600B, The strange fact is that when I turn off my led lamp keeps flashing fast, this is not the case with other types of lamps, only with LED lamps, the problem is only when it is Off when turned on works perfect. Has anyone ever experienced this?


  • 2
    \$\begingroup\$ Could you draw a schematic? It's annoying to have to figure out connections from that video. A datasheet for that module your TRIAC is mounted to would be useful too. \$\endgroup\$
    – user133493
    May 10, 2017 at 3:00
  • \$\begingroup\$ LED lamps often have low current draw and the leakeage/circuit current on the dimmer circuit is enough to charge the LED driver capacitors and then turn on for a moment. You need to use an LED compatible dimmer if you have to control small load. \$\endgroup\$
    – KalleMP
    May 10, 2017 at 5:04
  • \$\begingroup\$ Hi KalleMP, thanks for your help, today I tested 4 types of tria the smallest is the BT134 and unfortunately the same problem occurs. \$\endgroup\$ May 10, 2017 at 19:47
  • \$\begingroup\$ Do you have a snubber (series R and C) across the triac MT1 to MT2? \$\endgroup\$ Dec 8, 2019 at 16:26

2 Answers 2


Your Triac has excessive leakage and the LED AC_DC SMPS charges up and then discharges and repeats like a unijunction relaxation oscillator.

Either reduce the leakage or reduce the load impedance to the LED with a 4W AC bulb (Xmas or chandelier light) or put an X-rated plastic film cap 0.022uF to 0.047uF in parallel with the LED or triac load output to shunt some leakage which may not be enough.

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    \$\begingroup\$ X-Rated? You must have seen a different video. \$\endgroup\$ May 10, 2017 at 6:34

I've experienced this on several LED bulbs, usually the cheaper ones, but not always. There is some leakage though the triac. IGBTs tend to "close the gate tighter" and not flicker those cheap bulbs. Sometimes having more cheap bulbs on the circuit helps, but the qty varies widely in my unscientific experimentation.

If you're stuck with what you have, place a small dummy load on the circuit with the LED bulb. Old AC/DC adapters (heavy, non-switching) work well without heat, noise, or light (you don't even need to plug in the DC part). I use that method the most. Regular tungsten light bulbs are good as well; nite-lights included (as tony mentions). Or you could build some fancy circuit; i'm sure the experts around here have some suggestions.

  • \$\begingroup\$ Hi Dadavis, thanks for your help. Do you believe that IGBTs can work? Can you tell me some specific model, I'll buy it today. \$\endgroup\$ May 10, 2017 at 19:50
  • \$\begingroup\$ Hi dandavis, I did a test with Old AC / DC adapters and it worked, on the multimeter it measures 074.0V before adding the ac / dc, then it drops to 010.5v, and the lamp stops blinking, thanks for the tip, but I will need to solve This in the circuit because we will use in many places. I will try to solve using IGBTs. \$\endgroup\$ May 10, 2017 at 22:06

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