how to use transistors circuit as DPDT relay

Discussion in 'General Electronics Chat' started by Adam King, Nov 19, 2009.

  1. Adam King

    Thread Starter New Member

    Nov 19, 2009
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    Hi guys, i've been trying to build a circuit that would substitute a DPDT relay using transistors with full isolation, yet i am still no where.....any idea ???

    thanks
    Adam
     
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    How much voltage / current are you switching?
     
  3. Papabravo

    Expert

    Feb 24, 2006
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    What do you mean by "full isolation"? Normally you isolate either the inputs or the outputs, but not both.

    I don't think you can get behavior equivalent to a relay with a BJT. You might have better luck with a FET, or a BJT controlling the gate of a FET.

    Would some kind of opto-isolator possibly fulfil your requirements?
     
  4. Adam King

    Thread Starter New Member

    Nov 19, 2009
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    Well, I have a DPDT relay; one of the poles is connected to the positive lead of a capacitor “47MF- 16V” and one of the throws is connected to the positive of 12 V DC power supply, the third throw is connected to a transistor, the capacitor charges itself when the relay is OFF then when the relay turns ON the capacitor discharges itself into the transistor, so what I really want is to replace this mechanical relay with transistors circuit.

    Thanks
     
  5. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    A flasher? Helpful to post a schematic.
     
  6. Adam King

    Thread Starter New Member

    Nov 19, 2009
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    like Flip Flop?? it would be a good idea, i might get some hint, thanks
     
  7. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Ok then post YOUR schematic. What's it controlling? What's it's purpose?
     
  8. Papabravo

    Expert

    Feb 24, 2006
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    What about the other pole, and why the need for isolation?
     
  9. hobbyist

    Distinguished Member

    Aug 10, 2008
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    Is this any where close to what you have right now?

    dpdt.jpg
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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  11. hobbyist

    Distinguished Member

    Aug 10, 2008
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    This is just something to get ideas rolling.



    trelay.jpg
     
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