Need some basic help...

Discussion in 'The Projects Forum' started by Berserk, Nov 13, 2007.

  1. Berserk

    Thread Starter New Member

    Nov 13, 2007
    3
    0
    Hi,
    My electronics knowledge is a little bit rusty, and I'm hoping someone can help me designing a small circuit.

    I have a switch controlled signal giving GND when switch is not active and -6,75V when active. As an output, I want GND when the switch is active and not connected (just something else than GND) when the switch is released.

    My problem is that the control voltage (-6,75V) can maximum give a current of 0,06 mA, making it impossible to run a relay directly. I would also like to avoid any external power supply, but if there is no other solution, it's okay to use external PS.

    Any suggetions for the curcuit in between the input and output???
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    We have no idea of what your switch is controlling. As to the relay question, put a source on one terminal of the coil, and let the switch send ground to the other terminal to pull in the relay. If you still need to isolate the control from the signal, use a double pole switch.

    Changing the switch voltage levels is just a matter of rearranging wires - or so it seems as we have no idea what is actually going on.
     
  3. Berserk

    Thread Starter New Member

    Nov 13, 2007
    3
    0
    Okay, I'll try to be a little bit more accurate.

    I have two wires from an input, giving me GND and the control signal (GND/-6.75V), and I want two output wires giving me GND and control signal (GND/NC). It is going to be used as an interface converter between two different radio types.

    Hopefully, the attachment will make it more clear.
     
    • PTT.pdf
      File size:
      10.5 KB
      Views:
      20
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Will this work?
    gndout.jpg
     
  5. ashokcp

    Active Member

    Mar 8, 2007
    50
    2
    Isnt the resistor be in the base of the transistor?
     
  6. Berserk

    Thread Starter New Member

    Nov 13, 2007
    3
    0
    That should work.

    Thank you very much!
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    No. But one could add a base resistor for transistors unable to tolerate 60mA base current.
     
Loading...