Transistor advice

Discussion in 'General Electronics Chat' started by ajhoward, Nov 24, 2011.

  1. ajhoward

    Thread Starter Member

    Nov 16, 2011
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    How can I connect a pnp transistor with a switch at its base going to ground, which turns on when the switch is connected to ground which turns off a npn transistor. Then when the switch is open turns off the pnp which turns on the npn.
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    What are you trying to accomplish, a complimentary output switch of some sort?

    What are the voltages and currents to be switched?
     
  3. ajhoward

    Thread Starter Member

    Nov 16, 2011
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    I am using a reed switch to trigger a monostabe 555 timer, that triggers another astable 555 timer after a set period of time. I need something that when the reed switch open will pull the reset pin of the astable 555 timer to ground to silence the astable timer. I am using a 9V battery for a power source, not sure what the current values are.

    Take a look at what I have so far. Disregard the parts list and the back to front led (just threw that in haven't got that far yet), as I chopped and changed a few things, but I am talking about Q1 & Q2. Q5 is meant to power down part of the circuit after a short delay when the reed switch is opened again.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Since you are already using a relay, use a DPDT relay, so when the relay turns off, it holds the reset until the open switch starts the process over again?
     
  5. ajhoward

    Thread Starter Member

    Nov 16, 2011
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    I'm not using the relay in the parts list anymore, I ended up getting the solid state relay A210DN to keep the power consumption down. Thank you for your suggestion.
     
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