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Relay system for Halloween decorations

Discussion in 'Electronic Basics' started by [email protected], Oct 6, 2003.

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  1. Guest

    Hi...I wonder if this would be an easy project.

    I want to have a pressure switch under a doormat.
    When someone steps on the switch, I want a strobe light and cassette
    player to turn on, and run for approximately 30-60 seconds.

    Is this easily accomplished?
    I thought about a motion detector with X10 receiver and appliance
    module, but that would be over $100!
     
  2. Think more cheap PIR outdoor floodlight, the motion sensing ones, remove
    floodlight and use pir sensor and relay.
    Good place to look around:

    http://wolfstone.halloweenhost.com/HalloweenTech/MainHalloweenTech.html

    Adam
     
  3. Guest

    Thanks....I'm still on the lookout for a floodlight that would give me
    control over timing. I looked at the inexpensive Regent units today,
    and the minimum time before shutting off is 4 minutes.

    Regartding that subject: can I simply screw one of those
    light-socket-power receptacle adapters, or do I need to modify the
    unit?
     
  4. the Wiz

    the Wiz Guest

    As long as the device you're powering is within the current range of the
    controller, you're OK. If the floodlight unit is rated at 300 watts (two 150
    watt bulbs), then you can safely control about a 2 amp load.

    More about me: http://www.jecarter.com/
    VB3/VB6/NSBasic Palm/C/PowerBasic source code: http://www.jecarter.com/programs.html
    Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
    johnecarter [email protected] mindspring dot.dot com. Fix the obvious to reply by email.
     
  5. It should be simple and cheap to build, assuming you have the basic
    skills.

    You would trigger a 555 monostable with a -ve going input pulse. An
    improvised microswitch under the mat could be used, with appropriate
    connection to the DC supply to ensure correct polarity. Or, more
    expensive, a mat with inbuilt sensor, as used in commercial burglar
    alarm kits. The mono's output would drive an appropriate relay
    directly, assuming standard 555 with 200mA capability (100mA for the
    CMOS version). Mains to the strobe light and cassette player would be
    switched by the relay.

    If your trigger was a +ve going pulse, then you might use a circuit
    such as
    http://www.terrypin.dial.pipex.com/Images/555MonoEdge.gif

    You would of course need to change the RC values. In your case, for C
    you could use say a 68 uF electrolytic, and for R you could
    substitute a series combination of a fixed 220k with a 1M pot, to
    easily accommodate the range you specified. Or use any other Rs and Cs
    at hand, keeping the RC product constant.

    Alternatively (one of many) you could use the neat idea already
    suggested of a PIR, but add the 555 circuit to give you the variable
    timing. One approach would be to arrange for the mat to switch DC
    power to the alarm circuit, simultaneously triggering the alarm. A
    circuit using that approach is suggested at
    http://www.terrypin.dial.pipex.com/Images/555MonoByPU.gif

    Have you decided what you want to do about repetitive triggering?

    Please post back if the above is pitched at the wrong level.
     
  6. Guest

    I found a cheap Regent PIR.
    It has 3 wires: black, white, and red.

    I'm unsure which of the three wires is unused, assuming I'm using a
    2-prong extension cord (cut in half).
     
  7. Im in the UK and you realy want someone leaning over your shoulder to tell
    you exactly or the instructions must provide a pointer...
    But general scheme will be common neutral, live supply and switched live
    out, in Europe earth is common and three wire extensions.

    Adam
     
  8. JeffM

    JeffM Guest

    You've been watching too many movies
    where the bomb guy on the other end of a phone line says,
    "Cut the blue wire".

    The color coding might be white=neutral, black=hot, red=switched
    --then again , it may not.
    You'll have to take it apart to tell.

    Something else that no one has mentioned
    is that a solid-state switch (triac)
    generally has a minimum load requirement
    (has to pull at least X current, relative to full spec).
     
  9. Guess I'll assume it was then.
     
  10. Was trying to avoid allocating colours to connections, the instructions with
    the unit should help here...
    Most of the PIR floods I`ve encountered use a miniature relay, outside
    chance of welding it if relay operates jsut as strobe is firing, but very
    outside chance, if its a triac, use a ghost load out of sight, like a 40 w
    lamp.

    Adam
     
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