PIR motion detector

Discussion in 'The Projects Forum' started by allenpitts, Aug 12, 2011.

  1. allenpitts

    Thread Starter Active Member

    Feb 26, 2011
    Good morning All About Circuits,
    Using motion detector to fire timer cicuit to operate LED display.
    LED displays are beautiful and reliable.
    Finally figured out the 555 timer and have two circuits that I have adopted to accept the two second signal from the motion detector and extend the operation of the LED display to one minute. They are both timer circuit kits: the Velleman P2579 and the Can Kit CK002.
    A crude diagram of the system can be seen in
    motion_detector_w_LED_display_c.gif, attached.
    More data on the system can be found at
    Every thing works fine except the motion detectors. I have had four of the cheaper Quoruam G6547 PIR and they have all worked for a while and failed. So I purchased a more expensive Honeywell IS215t. It also worked for a while and quit working. (In fainess I think I fried one of the G6547 by connecting it to an unregulated power supply.) Begnning to think
    something about the system is killing the moption detectors. Bought a new Honeywell IS215t. I have read that when one is operating a relay with a signal it is a good idea to put a diode across the signal output. I was going to try that this weekend. Then I realized that I already have a diode, a light emitting diode, across the output. So I am out of ideas.
    Any ideas why the PIR motion detectors keep giving up the ghost?
    Allen in Dallas
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    I didn't find a wiring diagram for the Honeywell PIR. Could you provide it?

    In the datasheet it says it has an alarm relay, so there shouldn't be a problem with driving your relay, since it will probably be driven through relay contacts.

    The LED with the resistor in series can't work as a freewheeling diode. You'd need to connect a diode on the relay coil, it's cathode connected to the + pole of the DC-relay.

    Why are u using a 5V relay?
  3. HarveyH42

    Active Member

    Jul 22, 2007
    I've never fried Quoruam PIR, and have used/abused several. Always wanted to find a way to make use of the wireless portion... Anyway, they run off a 9volt battery, and believe they have a regulator to drop that down to 5volts. Haven't tried, but would probably survive a higher voltage. Don't think the output was intended to drive a load, but just to provide an alarm signal. Haven't messed with them in years, but kind of glad I bought several at $4.99... The new sales price is $8.99, last weeks flyer.
  4. allenpitts

    Thread Starter Active Member

    Feb 26, 2011
    Good afternoon praondevou,

    Searched everywhere for more info on the Honeywell IS215t. The data sheet is the only thing I can find.
    I assume a diode like a 1N4148 will work with cathode connected to the + pole of the DC-relay.
    The 5 volt relay is used because it is small enough to be tripped by the signal from
    motion detector.