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SCR Calculations

Discussion in 'Homework Help' started by jlacharite, Dec 1, 2007.

  1. jlacharite

    Thread Starter New Member

    Dec 1, 2007
    3
    0
    Hey everyone, I'm new here so bear with me ;).... I've got some calculations to do on an SCR firing circuit, I need to determine V_in based on the criteria given in the attachement. I don't know how to solve this circuit, any help is always greatly appreciated. Thanks

    J
     
  2. Nara Shikamaru

    Active Member

    Nov 24, 2007
    92
    3
  3. jlacharite

    Thread Starter New Member

    Dec 1, 2007
    3
    0
    hmmmm, i read your posts but I didn't see any calculations, Im trying to solve for V_in based on the two resistor values and Vcc @ 15v. How do you apply V_gt, I_gt and I_h to solve for V_in. Thanks again.
     
  4. Nara Shikamaru

    Active Member

    Nov 24, 2007
    92
    3
    if you have a R680ohms and you need minimum Ig =9mA so…
    Vin = 9mA* 680ohms = 6.12V

    That’s the voltage you need across the gate and the cathode….to activate the scr....i already prove it in my protoboard...and it works....i triggered a 12VDC Fan motor...so i hope its what you nedd....if not then dont hesitate to post again...see ya
     
  5. Nara Shikamaru

    Active Member

    Nov 24, 2007
    92
    3
    heres an schematic of what i did with your circuit....
     
  6. jlacharite

    Thread Starter New Member

    Dec 1, 2007
    3
    0
    Hey thanks a lot, I wasnt sure.... but that was the value I calculated too (without knowing it ;)) That really helps, what would the value of Vcc (15v) have to be to turn the SCR off? thanks again!

    Jesse
     
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