Timer circuit for relay

Discussion in 'The Projects Forum' started by zwalton, Oct 22, 2010.

  1. zwalton

    Thread Starter New Member

    Oct 22, 2010
    I am working on a project and could use some experienced help.

    The circuit need to do the following:
    1-Run off of DC battery source
    2-Have some kind of timer or clock
    3-At desired time or when timer expires, trigger the relay for at least 1 second
    4-Relay needs to fire some kind of motor or solenoid to open small door

    Anyone have any suggestions or advice?

  2. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    Yep. I have a great suggestion.

    Use the search function and look for 555 timer circuits.

    You WILL find exactly what you want.
  3. arunsjoshi

    New Member

    Oct 22, 2010
    My experience is that 555 based timers can work well only for short time delays of the order of a few minutes only, although the data sheet claim very long time intervals of even hours. The problem of getting long time delays is in finding a very good capacitor with low dissipation. Polypropylene capacitors work well but are not available in large values needed for long time delays.
  4. mbohuntr

    Active Member

    Apr 6, 2009
    555's can delay for hours fairly reliably, but if that won't work, try counters using "divide by (x) " IC's and a clock pulse. Calculate the necessary time required, and then use a 7555 as a monostable vibrator.
  5. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    From the OPs description he specify a period or time. Maybe he can tell us what it is actually going to be used for.
  6. marshallf3

    Well-Known Member

    Jul 26, 2010
    Period of time involved will have a lot to do with the best way of going about the design, but what he's asking is easily done if we know that.