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Sensor light protection

Discussion in 'Electronic Repair' started by F Murtz, Nov 18, 2012.

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  1. F Murtz

    F Murtz Guest

    What would the cheapest way to protect a sensor light from spikes?
    I live out of the city and when the power drops out every so often the
    sensing portion of sensor light blows, But the spikes are not enough to
    damage anything else.Keep replacing sensor lights.
    This time I might investigate sensor circuit and see what is faulty.
  2. N_Cook

    N_Cook Guest

    PIR sensor ?
    There is some safety routine that applies to some such PIR in the event of a
    powercut , they have to be reset, find the instruction manual
  3. F Murtz

    F Murtz Guest

    These are cheap and nasty thingos.when you switch them on once they set
    themselves, if you switch them twice in quick succession they stay lit,
    if you switch them off,wait 10 sec.then switch them on once they revert
    to pir operation, tried this and they do not work in sensing mode.
    I was thinking of some suppressor to put in circuit to protect against
  4. Leif Neland

    Leif Neland Guest

    F Murtz formulerede spørgsmålet:
    That is not a bug, it is a feature (tm)

    If you want to have the lights on permanently, you turn the power off
    and on again quickly.

    If you want to revert to normal operation, turn off for 10 seconds and
    turn on again.

    They are ment to work that way.

    What do you mean by "tried this and they do not work in sensing mode."?

    It is not spikes, which cause the trouble, it is the dropouts, which
    turns the lights on.

    Which means you either have to modify the lights to remove the feature,
    or power the lights from an UPS.

  5. F Murtz

    F Murtz Guest

    That is what I said, but it does not work that way any more

    After the drop out the light ceases to function as it is supposed to,
    none of the usual switch on once after 10 seconds for detector use or
    switch twice for permanent on works it is either permanently on or off.
    the light just acts as if it had no sensor in circuit.

    This is the third one I have to replace, all blowing up after supply
    May be I should fit a more expensive one but I would rather have some
    suppression or protection that works.

    I know how they are supposed to work but these dont.

    To date I have just chucked them and replaced but I will keep this one
    and dismember it and figure what is blowing.
  6. nesesu

    nesesu Guest

    I have seen two basic types of circuit: one is powered via a step down transformer [usually the fairly old designs] and the newer ones seem to be powered directly off line. In either case, a suitable "Transorb" Zener across the internal power rail of the sensor circuit should protect against transients damaging that part of it. The other sensitive part is the SCR/Triac that controls the lights. If it is blown, then replace it with a 800-1000V rated part and add a good sized 140V MOV across it. If the MOV fries, it will only turn the light on and not cause a fire.

    Neil S.
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