On Off circuit

Discussion in 'Homework Help' started by dave_is_sexy, Jan 16, 2005.

  1. dave_is_sexy

    Thread Starter New Member

    Jan 16, 2005
    Hey guys. I did electronics last year and now want toimplement some into my major project. Only trouble is I've forgotton practically everything.
    I need to make a circuit which can turn a light on via a switch being pushed and relesed - leaving the light on, and a different switch used in the same way to turn the light off. Ideally the 2 switches should have a common pole.
    Anyone got any ideas? I'd like to avoid relays and stick with transistor based circuits cos there's gonna be fields all over the place. It's really hard! :(
  2. beenthere

    Retired Moderator

    Apr 20, 2004

    Just use a latching relay. P&B makes a nice line thereof. For safety, use one with a 12 volt coil. I use one to control lights in the basement from four stations with pushbutton switches.
  3. Maxx

    Active Member

    Oct 30, 2004
    If you are using a DC lamp you could use a thyristor.

    Use one pushbutton to trigger the gate to switch the lamp on.

    The off button can be done in one of two ways, a normally open switch used to short the anode and kathode of the thyristor out, or a normally closed switch in series with the lamp, so that when the button is pressed it removes the supply and the thyristor no longer latches.

    There will be lots of example circuits available on the net for using a thyristor as a latch. it will only work with DC though as AC will switch off the thyristor conduction when it reaches the zero crossing point.

    Other ways would involve using a flip-flop or latch circuit but they would be a little more complicated compared to the thyristor.
  4. dave_is_sexy

    Thread Starter New Member

    Jan 16, 2005
  5. mozikluv

    AAC Fanatic!

    Jan 22, 2004