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Simple sleep timer circuit - how?

Discussion in 'Hobby Electronics' started by Michael, Sep 25, 2004.

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  1. Michael

    Michael Guest


    I would like to build a *very simple* "sleep timer" circuit to incorporate
    into a stereo system. It should switch the mains, and could even be in a
    separate small box. The idea is to press a button to give me power for one
    hour only.

    Anybody built/seen anything like this?

  2. Joerg

    Joerg Guest

    Hi Michael,

    In the US these are sold in hardware stores. A knob is turned to
    whatever time you want it on and it directly switches mains. Not much in
    there except a mechanical timer and a switch. Possibly they also have
    electronic ones. Mostly this is used to keep a fan on in the bathroom
    after a, well, you know, or to keep a spa pump motor running for a
    desired time.

    Should be available in Australia as well.

    Good Day, Joerg
  3. Ms_Squiggles

    Ms_Squiggles Guest

    Years ago I had a clock radio that the radio had failed..... I removed the
    radio circuit board and fitted a relay switching the mains, also a 3 core
    mains lead. The relay coil was 12 volt, to suit the
    switched DC voltage output from the clock circuitry. Where the speaker
    used to be, I fitted a small size power point outlet....

    Set the alarm and it would turn the hifi on at that time....
    set the snooze to play the hifi for an hour....
    use the radio on function switch to turn the hifi on for an indefinite
    period of time.

  4. Michael

    Michael Guest

    Thank you. :)

    Unfortunately the power outlet is hidden, but maybe the guts of the thing
    could be put in a box with a power cord.

  5. Michael

    Michael Guest

    What a fantastic idea!

    Thank you...

  6. Martin

    Martin Guest

    I would think that a simple 555 timer circuit would do this - set up as a
    one shot timer. Plenty of circuits on the internet, just Google for 555
    timer, and all parts available from Dick Smith/Tandy/Jaycar, etc, etc....
    The timer circuit can drive a relay - if you use a relay with suitably rated
    contacts then you could switch the AC....

    I built a 24v timer to turn the light in the back of a rescue truck off
    after 10 minutes - press a button and the timer starts, 10 minutes later it
    turns the relay off and the light goes off. Ran the circuit straight off
    the 24VDC power using a 12 volt regulator to run the IC and relay... You
    could do similar for 240VAC as the curcuit doesn't use much power so a very
    simple regulated power supply could be built to run the thing, if absolute
    precise timing isn't needed (i.e. 1 hour +/- 1 - 2 minutes..)

    To save some trouble I actually used the Jaycar timer kit and modified the
    circuit a little to suit my needs. Probably have the schematic here of the
    changed circuit, but try the Google trick first because 555 timer circuits
    aren't very difficult at all..


    Martin, VK2UMJ
  7. Theres a HUGE home autopmation industry that does this sort of thing.
    Its a big seller in the US at

    For 240V you can try

  8. Lord-Data

    Lord-Data Guest

    $29.95 at officeworks for a Belkin TimerCube ..

    these have gone sellthru, which means end of line .. but most stores
    probably still have stock at this point ..
  9. Unbeliever

    Unbeliever Guest

    Or maybe on the end of an extension cord? Look in the electrical section at
    Bunnings, maybe even at Kmart. Leave the guts behind the safety rated
    enclosure where they belong.

  10. Michael

    Michael Guest

    I have been away for a week, and have come back to all these replies. :)

    Thanks all for your suggestions. Ultimately I modified a clock radio by
    replacing the dial lamp (9VDC) with a relay, switching 240V to a socket on
    the back.

    This works a treat, and gives me all the clock radio functions, but I am a
    little uneasy about the safety rating, and will try some of your other ideas
    as well. (instead).

    Thanks again all of you,
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