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Very basic triac circuit problem:

Discussion in 'General Electronics Discussion' started by MidAtlantian, May 17, 2015.

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  1. MidAtlantian

    MidAtlantian

    36
    1
    May 12, 2015
    Hi,

    I am trying to use a triac in a very simple circuit. My circuit uses a MOC3041 isolator to trigger a BTA316 triac. I can wire the 3041 with a 9v dc circuit and an external LED and then I can see that the 3041 is turning on when I power the internal LED. But when I wire the triac to the 3041 - one side (pin 6) to the triac's gate (pin 3) , and the other side through a 150 ohm resistor to the load side of the triac, and turn on the 3041, the triac does not switch on. I am sure this must be as fundamental an error as one can make, but, well, here I am!

    Thanks for any suggestions,

    MidAtlantian
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,852
    Jan 21, 2010
    What current are you running the LED in the optocoupler at? And can you show us the circuit?
     
  3. MidAtlantian

    MidAtlantian

    36
    1
    May 12, 2015
    Hi Steve,

    I thought I had not posted this! I found my problem: I had the control loop going from the gate through a resistor into the load side of the triac. Wired to the supply side, it works fine. And yes, when the current through the LED was not high enough, that was a problem, but I'd got that far. :)

    However, thank you or your response. As far as posting a schematic, I do not have any software that makes that easy. Are there any you'd suggest? Especiallya more or less intuitive one, that I might not have to spend a lot of time learning.
     
  4. davenn

    davenn Moderator

    13,993
    2,019
    Sep 5, 2009
    Paintbrush in Windows is as good as any for doing quick schematics
     
  5. MidAtlantian

    MidAtlantian

    36
    1
    May 12, 2015
    Paintbrush? Yes, I guess you build a "master page" that you add to up as you need and create symbols. Easy. thanks.
     
  6. davenn

    davenn Moderator

    13,993
    2,019
    Sep 5, 2009

    yes indeed and here is a big start for you from my collection ...

    CCT_SYMB.gif


    cheers
    Dave
     
    Supercap2F likes this.
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,852
    Jan 21, 2010
    Digikey have an online schematic tool that I often use. You need to register for it but other than that it's free.

    Google "digikey schemeit" for more information.
     
  8. MidAtlantian

    MidAtlantian

    36
    1
    May 12, 2015
    Dave,

    Thank you!! That is quite a gift and saves me doing a lot of work. That looks like most of what I'd use.

    Funny, it is "just" one page, but there is really a LOT of stuff - and a lot of work - in it.

    MidAtlantian
     
  9. MidAtlantian

    MidAtlantian

    36
    1
    May 12, 2015
    Steve,

    That looks helpful, especially as it has an index of symbols with their names. Often I'll know the name of a component but not the correct symbol, but also, sometimes I'll come across a schematic where I don't know what the symbol means, so that should be useful. However, I'm some distance from telephone exchanges or optical cables, and my internet is often VERY slow, so relying on a link is not the best for me, but this looks very good too. Thanks.

    MidAtlantian
     
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