Connect with us

Triac Problem

Discussion in 'General Electronics Discussion' started by Abdullah Badarneh, Feb 26, 2018.

Scroll to continue with content
  1. Abdullah Badarneh

    Abdullah Badarneh

    3
    0
    Feb 26, 2018
    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.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
    2,830
    Jan 21, 2010
    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?
     
  3. Abdullah Badarneh

    Abdullah Badarneh

    3
    0
    Feb 26, 2018
    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.

    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.

    no, it's not connected with anything
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
    2,830
    Jan 21, 2010
    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).
     
  5. Abdullah Badarneh

    Abdullah Badarneh

    3
    0
    Feb 26, 2018
    the trigger occurs regardless the type of device, I tried to connect Samsung charger that connected to phone, the same problem occurred
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
    2,830
    Jan 21, 2010
    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.
     
  7. Bluejets

    Bluejets

    4,744
    999
    Oct 5, 2014
    Floating pins usually cause many problems.
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    11,413
    2,619
    Nov 17, 2011
    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.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-