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small circuit help needed

Discussion in 'Electronic Basics' started by Bob in PHX, Feb 20, 2005.

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  1. Bob in PHX

    Bob in PHX Guest

    To All,
    I have an interesting problem that I need to solve. I have an older
    electronic blackjack machine that has blown the coin hopper pay out circuit.
    No schematic of the board is available and the pcb has a 25 cent sized
    burned clean through it.... The good part is that I found a chip that puts
    out a 5 volt signal when the "jackpot" is hit and the coin hopper needs to
    start. This 5volt signal stops when the jackpot has been paid.

    I was thinking that a simple relay would work, but then I worried about
    pulling to much amperage out of the chip, which by the way is some sort of
    specialty chip, thus I don't know what the chip can stand. So, I figure that
    I need some sort of opto isolator chip that has a very small amperage draw.
    This chip would allow me to use a separate power supply to trigger the
    relay, with say a 2n3904 transistor.... I just don't know what chip to use
    that would isolate the 5v trigger lead from a separate 5v powered circuit.
    The two circuits would not share a ground.

    any ideas??????

    Bob in phx....
     
  2. John Fields

    John Fields Guest

    ---
    View using a fixed pitch font:

    +5V
    |
    +----+----+
    |K |
    [1N4001] [COIL]- - -|
    | | +--> |
    +----+----+ | |
    | O O--->TO COIN HOPPER
    C |
    5V TRIGGER>----[1000R]----B 2N4401 +-------->TO COIN HOPPER
    E
    |
    GND>------------------------+
     
  3. Bob in PHX

    Bob in PHX Guest

    AWSOME!!!!!!!! Only two questions. What is the [1000r]. I am guessing a
    1000 ohm resistor?????

    Second, the ground show comes from the second power supply or from the same
    ground as the trigger???

    Thanks for the design and in advance for the answers to my two questions!!!

    Bob in phx
     
  4. Rich Grise

    Rich Grise Guest

    For the circuit[0] to work as shown, both grounds (for the trigger source
    and for the relay supply) need to be common (connected together). Since
    the relay contacts are isolated, it doesn't matter where ground is in the
    payout circuit, as long as the difference doesn't break down the relay
    insulation, which is very unlikely.

    Good Luck!
    Rich

    [0]
     
  5. John Fields

    John Fields Guest

     
  6. Bob in PHX

    Bob in PHX Guest

    Thanks for all the help... Ill try it out this week and report back the
    results!!!!!

    Bob in phx
     
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