Building a PIR Motion Sensor Circuit on a Breadboard

[@captainprototype187]

I cannot be the only one who discovered these great tutorials.

[@alessandrog5261]

Thanks. It would be very interesting a circuit about how to build a timer for this kind of sensor. Keeping the lights on for a certain amount of time like 2-5 minutes

[@quickstartworkbook1532]

Some motion sensors enable you to set the amount of time the signal stays high for. I've got one set up in my shed so that the LEDs stay on for about 3 minutes. I used a 12v battery with 4 LEDs and no resistor.

[@tscherer1982]

I don’t understand the transistor…doesn’t the PIR already act as a switch like in the first circuit?

[@quickstartworkbook1532]

The problem with the first circuit is that the output from the pir sensor wasn't really powerful enough to properly illuminate the LED. If I remember correctly, it was only about 3mA, and you need something more in the region of 10mA at least. So what I decided to do was to use the 3mA is switch on a transistor which then allows current to flow directly to the LED without going through the sensor. Basically, the sensor isn't capable of driving a device itself, but is perfect for providing a small current to switch on a transistor.

[@hello2803]

My circuit isn’t working and I can’t figure out why

[@quickstartworkbook1532]

Which of the two circuits are you trying to build?

[@hello2803]

@@quickstartworkbook1532 Ive tried both, think it’s my sensors that aren’t working