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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.


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


...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.


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.

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.

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


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?

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


8 years ago

 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.