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One Light, Two Supplies

Discussion in 'Electronic Basics' started by No. 1 Novice, Aug 14, 2006.

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  1. No. 1 Novice

    No. 1 Novice Guest

    I have recently installed an outside light which is switched usind a
    pir, however I want to install a second pir at the other end of my
    garden to also switch the same light on when movement is detected. the
    second pir has a power supply right next to it so I was wondering can I

    use the 2 suplies, 2 pirs and one light safely, my main concern is that

    whe pir 1 is on then if pir 2 switches will the two seperate supplies
    conflict with each other? any advice is greatly appreiciated. Thanks

    Reply »
     
  2. Tom Biasi

    Tom Biasi Guest

    I have recently installed an outside light which is switched usind a
    pir, however I want to install a second pir at the other end of my
    garden to also switch the same light on when movement is detected. the
    second pir has a power supply right next to it so I was wondering can I

    use the 2 suplies, 2 pirs and one light safely, my main concern is that

    whe pir 1 is on then if pir 2 switches will the two seperate supplies
    conflict with each other? any advice is greatly appreiciated. Thanks

    Reply »

    Are the PIRs actually supplying the power or just switching?
    If they are just switching there is no problem with parallel open contacts
    working together.
    If they are supplying power you could isolate each with a diode.
    Tom
     
  3. default

    default Guest

    Are these both 120 or 240 VAC mains supplied lights, or DC supplied
    lights?

    It can be done no problem but the way to do it will depend on what
    types of PIR and the supply voltage(s) in each case.

    They should be on the same supply (same circuit breaker) if they are
    working from the power mains - Then there still might be a a problem
    with the electrical code.

    A way around would be to add a relay from one of the PIR's to switch
    the light on in parallel with the other PIR.

    Low voltage DC lights would be different. LV AC lights different
    again.
     
  4. No. 1 Novice

    No. 1 Novice Guest

    Both Pirs are fed from the same lighting circuit, each PIR I believe
    are simply switching the power to the light (each has 3 cores, mains
    240v supply, neutral and switched supply) on both PIRs I've wired the
    switched supply and neutral to the light. So if either PIR detects
    movement the light will come on, will this be OK if the second PIR
    detects movement (and the switch closes)whilst the light is already on
    (from the first PIR detecting movement)?
     
  5. Tom Biasi

    Tom Biasi Guest

    Sounds good, if the switches are in parallel. Could you "draw" a diagram or
    point to one?
     
  6. default

    default Guest


    This is a 240 volt light? What function does neutral serve? Hot is
    240 and neutral is zero? Plus a ground for safety?

    Here we have a center tapped transformer - 120 volts to neutral. Hot
    to hot is 240 VAC - ordinary appliances are 120 as are most of the
    outlets. Neutral and Ground are brought out to all 120 V switches and
    outlets. Neutral and ground are connected to earth ground at the
    circuit breaker panel.

    If both PIR's are switching the same source of power, there should be
    no problem in parallel switching and allowing either to turn on the
    lamp. A very good idea - before hard wiring a connection - would be
    to put a lamp load on both PIR's (to acertain that they are both
    working and to give them both a load in case they use triac outputs -
    relay outputs wouldn't be a problem) Wire an AC volt meter between
    both switched outputs - with both PIR's activated, at the same time,
    there should be zero volts between both switched outputs.

    If you get zero volts with both on - I'd go ahead and hard wire them.

    Potential problems:

    They make a replacement PIR lamp fixture that has a feature that
    allows one to flip a switch inside the house off and on and that
    leaves the fixture turned on indefinately - ignoring the PIR - no
    telling how that might behave if you are using one of that type of
    fixtures . . .

    There is another concern . . . when you parallel circuits this way -
    with two PIR's apart in diffrerent locations - each supplied with
    voltage - someone working on a pir circuit or the lamp circuit may
    disconnect the hot wire from one PIR and figure it is safe to work on.
    If the other pir is activated it would back feed voltage to the
    supposedly "safe" circuit.
     
  7. jasen

    jasen Guest

    should be ok as long as both PIRs are connected to the same circuit

    But, check the documentation for the devive you have.
    if it's allowable to parallel the PIR with a switch what you plan is OK too.

    Bye.
    Jasen
     
  8. No. 1 Novice

    No. 1 Novice Guest

    THANKS TOM, I'VE GOT A DIAGRAM BUT NO E-MAIL ADDRESS TO POST IT TO. CAN
    YOU SUPPLY ONE FOR ME?
     
  9. Tom Biasi

    Tom Biasi Guest

    Just reply to this post. Remove anti-spam marks.
     
  10. No. 1 Novice

    No. 1 Novice Guest

    Sorry Tom I really don't know how to do that.
     
  11. Tom Biasi

    Tom Biasi Guest

    Doesn't you browser have a 'Reply' button? If you hit 'Reply' instead of
    'Reply group' you will open an email to me. It will be obvious that I added
    marks to thwart spam.
    Tom
     
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