Momentary to constant switch

Discussion in 'The Projects Forum' started by Sn95stang, Feb 2, 2013.

  1. Sn95stang

    Thread Starter New Member

    Feb 2, 2013
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    I need to make a switch that takes a momentary signal(I would have to scope the signal to get details) 12 volts, 200milliamps and output a constant 12 volt 2amp signal. I would also like to have the same momentary signal turn off the constant signal.
    I have accomplished this with 4 relays that latch and unlatch. That setup was unreliable. I am thinking the way to go is to use a logic module and drivers to accomplish this.
    Any thoughts? I have never built a circuit board before, I'm thinking this would be a simple project to start with. Thanks for any help in advance
     
  2. #12

    Expert

    Nov 30, 2010
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    I was playing with this a couple of weeks ago. It might not fit your need perfectly, but you can post more questions after you examine it.
     
  3. Sn95stang

    Thread Starter New Member

    Feb 2, 2013
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    Thanks for the help, give me a min to research how this works
     
  4. Sn95stang

    Thread Starter New Member

    Feb 2, 2013
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    I guess my first question is how do you get a transistor to stay on with a single pulse of power?
     
  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    You can do it with a flipflop and a p-channel Mosfet. In the below picture I used 15V but 12V work too. Every rising edge of the input signal will change the output signal. Note that in this circuit the Source voltage and the power supply voltage of the IC must have the same voltage.
    [​IMG]
     
  6. #12

    Expert

    Nov 30, 2010
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    In the circuit I posted, the third transistor (counting from the left) turns on the pnp transistor which provides positive feedback to the base of the third transistor.
     
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