Simple Light Activated 12V 2 Amp Switch

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.

Reply to
BeeJ
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It happens that BeeJ formulated :

Maybe some parts I can pick up at Fry's.

Reply to
BeeJ

Can you go inside the receiver and tap some signals? You could drive a logic-level mosfet gate with just a few volts.

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Reply to
John Larkin

  1. Replace LED with an opt-isolater.

Google for opt-isolater and you can find the rest.

Reply to
hamilton

Maybe just some sort of relay for the final switching? How many times will it turn on and off?

George H.

Reply to
George Herold

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.

Reply to
BeeJ

We have plan for using this chip:

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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.

Reply to
Edward Lee

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.

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Reply to
Peter Heitzer

Maybe you could canibalise parts from one of those solar powered garden lights.

You could drive an optocoupler in place of the regular white LED, but bear in mind the lower Vf.

Sometimes they're discrete component so you can get at the transistor that controls the LED drive inverter, the last one I pulled apart was a "black blob" chip - but it would be just as easy to hook up an opto coupler/SSR.

They're usually run from a solar panel charged single AA NiMh - I've seen a

2x AA with an impressive solar cell, but that also had UV LEDs & a bug-zapper.

Obviously the LED/opto coupler/SSR is on when there's no daylight falling on the solar cell.

Reply to
Ian Field

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?

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Reply to
Jasen Betts

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

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Reply to
Jasen Betts

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