Turning on SCR

Discussion in 'The Projects Forum' started by unfettered, May 4, 2014.

  1. unfettered

    Thread Starter New Member

    May 4, 2014
    Circuit I am working on has been taken from this site -

    Aim of this circuit is to turn on the SCR( i am using C106mg) with adjustments by a variable resistor of 100Ω , so that the current will flow through the coil and trip the circuit ( from NC to NO ) in case of overload .For load , i am using a 12 V LED .

    Problem I have faced so far -
    1.) Appropriate rating of the relay I should use in the circuit for 10-12V dc supply .I was usig a 6v relay but i think i should replace it with a 10v relay .
    2.)The SCR has not been turn on despite configuring the circuit as instructed .

    I am pretty much confused regarding the scr , variable resister arrangement .So far when i turn on the switch , circuit is working in normal condition i.e. LED is glowing .Varying the Variable resistance affects the glow of the LED . Despite this , SCR dosen't turns on when i try to short circuit at load .

    My question are -
    1.) is the circuit given is correct ?
    2.) do i need to modify the circuit 's scr arrangement ?
    3.) as a variable resistor , what I got is a carbon-linned trimpot . Is grounding of 3rd pin necessary ?
  2. bertus


    Apr 5, 2008

    The given circuit shows the relays in the wrong position.
    When the relays is not powered (as shown) the contact should be in the NC position.

    The scr will trigger when the voltage on the gate will reach about 0.6 volts.
    See the datasheet for more info: