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Is it possible to make a PIR sensor turn a small electric motor? Answered

I need to have a PIR sensor turn a modded servo, but i can't get it to work. The servos electronics have been taken out, so its just a gearbox, and works like a normal motor. I have tried using a transistor as a switch for the servo, it works for an led, but when the motor is put in the leds place it just spins non stop. I have no clue what else to try, or why its acting to erratic. I have also tried just going straight from the PIR sensors output, but no luck there either. Does anybody know how to do this without a micro controller? and could you provide a schematic. Thanks.

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steveastrouk (author)2010-01-08

Add a resistor from +supply to the "output" pin, say 1K, NOW you'll have base drive.

Steve

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...as a note, the outputs of these sensors are often "open collector" transistors, so it needs to see a real load to change voltage when it switches.

Steve

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orksecurity (author)2010-01-07

Possible, yes. Complexity depends on what you want to do.

If you just want the motor to run when IR is detected, all you really need is an amplifier (or a threshold detector if you want on/off rather than speed depending on signal strength) driving an appropriate output stage (solid state or relay as appropriate.) That's basically what your standard motion-detector light fixture is doing.

If you want it to respond to patterned signals -- eg a remote control -- then you need something to decode that serial data. A microcontroller is probably the simplest solution for a hobbyist.

Given how many PIR projects are shown under "Related" at right, I suspect you can find something there which could be adapted to your project.

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adem70 (author)orksecurity2010-01-08

I am simply trying to get the motor to turn when it senses motion, I am using the diagram here.  IT works perfectly when the motor is replaced with an led, but the motor spin continuously. I am not sure on the values of the Sensor, I ahve it laying around. But the led is a 12v.

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adem70 (author)adem702010-01-08

it is a 2n2222 transistor so it should work, maybe i need resistance?

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Re-design (author)2010-01-07

You should be able to do that with just a transistor.  But you may have tried to use the wrong one.  What did you use? And which pir sensor did you try?

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adem70 (author)Re-design2010-01-08

I am using a 2n2222 transistor, I have a schematic for exactly what im trying posted as a reply to orksecuirty.

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gmxx (author)2010-01-07

 youre going to need a microcontroller.  

im going off the specs for the parallax pir sensor (seems to be the most common.) it should be the same for other pir sensors

it works by outputting a high or low signal on a pin. the current it outputs will not be enough to turn a motor.

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