Dark Activated Switch

Discussion in 'The Projects Forum' started by donnierod, Mar 20, 2012.

  1. donnierod

    Thread Starter New Member

    Mar 18, 2012
    Okay, I want to build another dark activated switch. The first one I built 2 years ago works fine and still in use.

    What I have use is the schematic on the left what I want to build is the one on the left.

    I started thinking, would this circuit work without the use of a relay?
    I don't know because I haven't tried it.

    So do you think it would work without the relay? Leaving the circuit as is, removing the relay and just hook up the LEDs with resistors to where the relay is, do you think this will work?

  2. #12


    Nov 30, 2010
    No. The LEDs need to be in series with each other...and you won't need the diode if there is no relay coil.
  3. wayneh


    Sep 9, 2010
    I agree on the diode, but differ on the LEDs. I think it can work, but I'd start with a higher value resistor until I could be sure not to ruin the LEDs. If you plan on 5-10mA each, your odds are OK. If you shoot for near the max current spec of the LEDs, your odds are low.
  4. donnierod

    Thread Starter New Member

    Mar 18, 2012
    Thanks for your responses.

    I put 100 Ohm, but should of put 150 Ohm, according to a resistor calculator I uses. The other thought was to add a 470 Ohm resistor to each LED and then hook up each leg one to the "+" side.

    I wasn't sure on the diode and now I am.

    Thanks for the info!