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Switch on a light box for 45 seconds

Discussion in 'Electronic Design' started by [email protected], Feb 20, 2005.

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  1. Guest

    I work at a museum and would like to hook-up a light box to some kind
    of switch that would have the box stay on for about 45 seconds and go
    off. Any ideas?
    Thanks
     
  2. Guest

    I am assuming you want it to work like this: the user pushes a button,
    the light box comes on, stays lit for 45 seconds, then turns off until
    the user pushes the button again. I am also assuming that the light box
    operates on regular wall-socket voltage from a regular wall socket, and
    that you have someplace to put the control circuit.

    If the above is true, then what you probably want is a "delay on break"
    or "delay on release" relay. This is a relay (an electrically operated
    switch) with an internal timer. There is a knob on top of the relay
    that sets the time it stays on. These relays are usually designed to
    plug into a standard socket, so you'd need to get a socket as well. You
    also want to make sure you can get one that can be triggered by an
    external (pushbutton) switch. You'll probably want to use a fairly
    beefy pushbutton (like the ones used on arcade games) so it will last.

    At the local electronics distributor, I can get a suitable relay and
    socket for about US$65. Add another US$20 or so for a pushbutton, wire,
    etc. The relay and socket will fit in a 3" (75 mm) cube. You'll have
    a plug, a cord, the relay socket, the wiring to the light box, and the
    wiring to the pushbutton.

    If you're not familiar with wiring up things that plug into the wall,
    get someone that is to help you with it. It's not that hard to do, but
    the consequences of getting it wrong can be severe.

    Matt Roberds
     
  3. Dan Mills

    Dan Mills Guest

    Over here you can get light switches that do exactly this (intended for use
    on staircases) maybe possible?

    The other thought I have is that a photographic enlarger timer does what you
    need.

    Regards, Dan.
     
  4. Might also look into using a motion detector wall switch, aimed as would
    need to wave hand in a space to activate it. Not sure if can get one
    with the exact time period you want or be adjustable to that.
     
  5. Chris

    Chris Guest

    If you'd like a store bought solution, stop by a camera store and look
    at their darkroom timers. Gra-Lab is a good source for this in the
    States.

    If you'd like something a little less expensive, get a 12VDC wall wart
    and the Velleman MK-111 Interval Timer kit. It uses a 555 and a relay
    to give you exactly what you need. It includes circuit board and all
    components except the wall wart. The relay will switch up to 3 amps at
    120VAC.

    Questions of this type usually receive a better response on
    sci.electronics.basics.

    Good luck
    Chris
     
  6. Alan Turner

    Alan Turner Guest

    I'd go to a hardware store and ask for one of those timers which runs a
    bathroom extractor fan for a fixed period after the light is turned off.

    An off-the-shelf solution will almost certainly be cheaper than a
    homebuilt one once you factor in the cost of putting it in a box,
    providing a power supply for the electronics, etc.

    Alan
     
  7. It's not clear which of these you want:

    a) a ready-made, shop-bought circuit just requiring careful
    connection (by someone qualified, possibly yourself, as presumably the
    box is mains-powered)

    b) a circuit you can build

    If the former, then you've had several recommendations.

    If the latter, then you could base it on these circuits:
    http://www.terrypin.dial.pipex.com/Images/555MonoByPU.gif
    http://www.terrypin.dial.pipex.com/Images/555OneShot.gif
    http://www.terrypin.dial.pipex.com/Images/555Mono+Driver.gif

    with suitable Rt and Ct. For example, combinations such as
    500k 82uF; 1M 39uF; 2.7M 15uF etc
    give the required delay.

    You haven't specified power supplies, or switch type, so adapt as
    necessary.
     
  8. Kim  Sleep

    Kim Sleep Guest

    A1 electronics in Toronto sells a 555 timer kit that will do what you need,
    with all components, circuit board etc, for $11.00, and a enclosure for
    another $4.00. It is adjustable from seconds to hours with a on-board pot.
    All prices are Canadian $, and you can find them on the web.
     
  9. Fred Bloggs

    Fred Bloggs Guest

    This is a straight forward application of a timer relay. Press the
    momentary switch, the relay applies power to the load for 45 seconds and
    then removes power- regardless of the state of momentary switch after
    the initial press. If you want the momentary switch to override the
    time-out, then jumper terminal 8 to 2. This will cause the power to be
    removed at the later of switch release or the 45 second time-out. There
    are so-called OFF-(MOM)-ON type switches where the push action can make
    it either momentary or permanently on which may be useful for that mode.
    If this is for a viewer activated display, then you would not want this
    mode of operation- do not jumper 8-2. Mate the line feed solid copper to
    stranded 14ga type to make the 0.25" crimp terminal connections- do this
    with wire nuts. All of this can mount in a standard wall mount switch
    box. Avoid any web based so-called electronic projects or hobby type crap.

    View in a fixed-width font such as Courier.





    NEMA ENCLOSURE
    +------------------------------------------------------+
    | |
    NTRL |(WHITE)
    | | to lamp
    | | +---|--->
    | | --------------- | |(BLACK)
    | | / /| | |
    LINE | +----HRDS4XX----+ | | |
    | | | | | | | | |
    | | +--------|---------+ | | | | |
    | | | | | _|_ _|_ | | | |
    | | | | | 8 1 | | | |
    | +-----------+ | | | | | |
    | | | | | +-------|3 2|-------X |
    | | | | | | | | |
    | | |o | | | | | |
    | | --| | | | | | |
    | | |o | | | |4 | | |
    | | | | | | screw | | |
    | | +--+ | | O | | |
    | | | | 5 | | |
    | +-----------+ | KNOB __ | | |
    | momentary | | | |
    | sw +---------------+/ |
    | |
    | ~ 3 x 2 x 1.5 inch |
    +------------------------------------------------------+

    X= wire nut junction

    See: http://www.ssac.com/catalog/HRDS1A01.pdf
     
  10. Fred Bloggs

    Fred Bloggs Guest

    I'll say- all that GraLab stuff is over-priced glitz, even a foot switch
    is $60- any kind of electronic timer $200.
     
  11. Fred Bloggs

    Fred Bloggs Guest

    I don't like that suggestion and I'll tell you why: you go buy that
    retail trash and what you end up with is an inferior imported knock-off
    product cashing in on the reputation of the American made product at the
    high price- plus the timing interval on those is in the 5-10 minute range.
     
  12. They're probably only making 10% of the quantity per year that they
    used to make. Maybe less with all the used stuff floating around.


    Best regards,
    Spehro Pefhany
     
  13. Rich Grise

    Rich Grise Guest

    They're probably only making 10% of the quantity per year that they
    used to make. Maybe less with all the used stuff floating around.[/QUOTE]

    There are a couple of Gra-Lab timers on ebay right now for about $25.00.

    Problem is, you'd have to preset it to 45 every time.

    Actually, Fred Bloggs's suggestion looks reasonable.

    Cheers!
    Rich
     
  14. Ken Moffett

    Ken Moffett Guest


    If yoe are interested in an off the shelf solution look at:
    http://www.cowlacious.com/TimerProd.htm
     
  15. Rswww.com part number 490-194 for example.

    Cheers
     
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