Keeping a Transistor on.

Discussion in 'The Projects Forum' started by Zatnikitelman, Jun 6, 2009.

  1. Zatnikitelman

    Thread Starter Active Member

    Jul 17, 2005
    I've got an interesting problem. I'm working on a project which will rely on one momentary N.O. pushbutton to activate two systems in order, then another N.O. pushbutton to reverse the first system.
    So it works like this:
    1. Press N.O. Button, system1 activates.
    2. Press N.O. Button, system2 activates and can reactivate whenever button is pressed.
    3. Press second N.O. button, system1 goes in reverse.

    I know it's possible to wire a relay back on itself so there is a constant flow of current to its coils and it stays energized unless the loop is broken. I need to know if it's even possible to do this with standard NPN or PNP transistors and how to do it.
    Don't worry about what the systems are, just assume they're simple on-off.
    I've been using the circuit simulator at (brings up Java applet) to try to work this out myself, but can't seem to attach the wire in the right place using the Circuits->Transistors->Switch circuit provided.

    If you're now curious what it is, it's my namesake, a Zatnikitel from Stargate SG-1 which only has two buttons: fire/activate and close. System1 is the motor or solenoid used to raise the Zat, and system2 is a sound effects board from RadioShack that has a simple on/off switch I can wire into this thing.

    Thanks for any help,
  2. PRS

    Well-Known Member

    Aug 24, 2008
    I'm not quite sure what you want. A normally open switch activates system 1. That's easy enough. But here's my question: now you press that same switch again and it activates system 2? And if it is pressed again it keeps reactivating system two which must be a one shot deal, huh?

    But what do you mean by pressing button 2? What constitutes system1 going in reverse? You need to be more specific.
  3. mbohuntr

    Senior Member

    Apr 6, 2009
    Will this work? button one = count up, button two = count down. use the binary number to activate/de-activate relays. Or SCR's using the second relay to break the current.
  4. hobbyist

    AAC Fanatic!

    Aug 10, 2008
    From his description of what it's used for it sounds like he wants to use the
    one button to open a door, then use the same button to fire his sound effects, as many times as he pushes it, then use the second button to close the door.