Timer Switch

Discussion in 'General Electronics Chat' started by King Amada, Jun 5, 2014.

  1. King Amada

    Thread Starter New Member

    Jun 15, 2013
    Good day, Please i have 2 bulbs/leds, one is green and the other is red. I want to put a time switch between them so that after 10 minutes the red switch off and the green lights up and vice versa till i switch it off. So do you know of any switch that i can use for that purpose, that will operate under 12v, like 5v. Please thanks.
  2. pwdixon


    Oct 11, 2012
    How about a 555 timer?
  3. samuel.whiskers


    Mar 17, 2014
    A 555 astable circuit will do it, one LED wired from the 555 output to GND, one to Vcc and they will alternatley flash as you have asked. 10 minutes might be a stretch for a lone 555....

    Use the 555 output on the clock input of a binary counter like a 4020, wire the leds to one of its outputs and you can have almost any time you want within reason....
  4. ScottWang


    Aug 23, 2012
    If you only want to using one 555 then you can choosing 7555 CMOS type, don't use the normal NE555, if you need some more time then you can using NE555 + CD4020 or CD4040.
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
    I think a 20 minute cycle is a stretch even for the CMOS 555. Capacitor tolerance and stability will be difficult issues, and calibration will take forever.

    OTOH, a 4060 running at 13.65 Hz will do this, or two 4060s to get a higher freq clock. Rather than have three transistors to drive the LEDs, you could use a 555 as a bipolar driver to meet the forum requirement.

    But I don't think the OP is asking about a circuit; I think he wants advice about a purchasable device such as an industrial cycle timer. Expensive, but off the shelf.

  6. inwo

    Well-Known Member

    Nov 7, 2013
    absf likes this.
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
    Or, another old trick that will have more closely matched currents:

    Pick LEDs with different Vf's, such as 1.8V for red and 2.1V for green.
    Single bias resistor from V+ to both anodes.
    Green cathode directly to GND.
    Red cathode to the drive transistor collector or 555 output.

    When the Red LED lights up, it starves current away from the Green one.

  8. MrCarlos

    Active Member

    Jan 2, 2010
    Hello King Amada

    There is not a simple switch that can produce the effect you want.

    It all depends on how much current is required by LEDs to light.
    And how long each should make the change.

    You say you want to make the change every 10 minutes and has a switch to turn it off

    The 555 can not work at that range. According to the manufacturer National Semiconductor. </SPAN>

    For that reason recommends: samuel.whiskers, to use a binary counter 4020.
    This is to achieve the amount of time you are requiring.

    The 7555, Recommended by: ScottWang , could be helpful but you are in the highest range (10 minutes ) according to manufacturer's specified INTERSIL .

    In addition to the circuitry to achieve the times you mention, you will require a power supply to power the circuitry.

    But, I think, that there are some devices that can achieve what you intend.

    You can check eBay.com , as INWO recommends.
    Or others, surely there are more providers of these types electrical-electronic devices.