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Simple Light Activated 12V 2 Amp Switch

Discussion in 'Electronic Design' started by BeeJ, May 16, 2013.

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  1. BeeJ

    BeeJ Guest

    Looking for a way to build a Simple Light Activated 12VDC 2 Amp Switch.

    I have a motion detector that radios to an alarm. Both are battery
    operated. The alarm has a pizo speaker and LEDs that are active when
    motion is sensed.

    I would like a simple circuit something like a photo-transistor capable
    of handling 12 VDC at 2 amp switching to run a windshield wiper pump
    from a 12V gel battery. A diode across the transistor collector to
    emitter to protect from motor spikes.

    I could also use the the audio out as the trigger but I don't think I
    can find a cheap and simple microphone controlled switch that will
    handle the voltage and current.

    Suggestions please.
  2. BeeJ

    BeeJ Guest

    It happens that BeeJ formulated :
    Maybe some parts I can pick up at Fry's.
  3. hamilton

    hamilton Guest

    1. Replace LED with an opt-isolater.

    Google for opt-isolater and you can find the rest.
  4. Maybe just some sort of relay for the final switching? How many times
    will it turn on and off?

    George H.
  5. BeeJ

    BeeJ Guest

    BeeJ explained on 5/15/2013 :
    The transmitter and receiver are weatherproof so I do not want to mess
    with wiring.

    If I had a phototransistor connected to a power transistor I could use
    that to drive the pump. Looking for recommendations on parts to do
    this. Or some other non-hardwired way. also I could easily swap out
    the receiver for another unit easily.
  6. Edward Lee

    Edward Lee Guest

    We have plan for using this chip:

    TTL/CMOS logic in

    upto 15V 1.2A (3.8A peak) out

    You should be able to run it for a short time at 2A.
  7. Or he could put the LED of an optocoupler in series with the LED in the detector.
    If the detector is operated with more than 2 AA/AAA cells, the 1.3 V drop for
    the IR-LED would not harm. The transistor could drive a small relay.
  8. Jasen Betts

    Jasen Betts Guest

    Nah, you have to put the diode across the motor.

    can you open the receiver an connect directly to the LED, the problem
    gets about 20 times simpler if you can.

    what's this for, controlling other peoples pets?
  9. Jasen Betts

    Jasen Betts Guest

    perhaps not all that easily, maybe you'd have to paint the case black to
    keep stray light out etc...
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