Electronic Solid State Relay Circuit

Discussion in 'General Electronics Chat' started by Kiks, Feb 24, 2011.

  1. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
    0
    [​IMG]
    from this circuit,
    What is the purpose of Q1 and R4 & C1? TIA.
     
  2. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    R4/C1 form a snubber across the triac to minimize switching noise and prevents turn-on surges across the triac.
     
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  3. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    The LED current passes through R1. When the LED current is about 15ma or so, there will be 0.6 volts across the B-E junction of the transistor (E = IR = 0.015 * 43) which turns it on. This causes its C-E junction to begin stealing current from the LED. As the current through the LED drops, less voltage will be developed across the BE junction, turning the transistor off which allows the LED to receive more current. This repeats itself continuously. Long story short, its a 15ma current regulator.
     
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  4. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
    0
    with the R2 and R3, how they come up to these value? same question goes to R4/C1 snubber. TIA.
     
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