PIR Motion Sensor

[FrankT]

I'm trying to get one of those cheapy PIR motion sensors to work but I am struggling.

I've gone through about 3 now and they all seem to die the same way.

The module is similar to this...
http://www.ebay.com.au/itm/HC-SR501-PIR-Motion-Sensor-Module-Arduino-Raspberry-Pi-ESP8266-/191621495655

And from what I've been able to determine the module has a 3.3v regulator to power the board, a BISS0001 controller, and a 1k resistor between the Out connection and pin 2.

I want to drive a couple of relays, so I run the output directly into the base of a NPN transistor (PN100), emitter to ground, and collector is 12v + 1k resistor + LED, to start with.

The first problem is the LED never goes fully off.

So I remove the LED and run the output through an 800k resistor to ground and just measure the voltage - and it looks correct, about 3.2v when on.

Because I can't find any detailed data on what the BISS0001 output circuit looks like, I start playing around.  Direct driving the LED from the output.  I even tried using a pull up resistor.

After the fiddling, things start going really wrong.  Now, the voltage on the output pin is showing 11v.  Given the circuit runs on the 3.3v regulated supply, I can only imagine I have somehow toasted the voltage regulator.  I have the current limited to about 50mA so I don't think it was a short.

So, I guess the first question is, does anyone know what is the output driving circuit of the BISS0001?

[StillTrying]

The output of the BISS0001 is the output of it's op amp, ~10mA.
The good news is that its supply can be up to 20V. 

Google BISS0001 or HC-SR501 PIR until you find your board.

https://www.mpja.com/download/31227sc.pdf

[Kilrah]

I want to drive a couple of relays, so I run the output directly into the base of a NPN transistor

Umm, what about a base current limiting resistor?

[FrankT]

Thanks, that pdf seems to describe my board.

The circuit already has a 1k resistor inline with the output, so the base current should be limited to max 3.3mA.

[StillTrying]

I want to drive a couple of relays, so I run the output directly into the base of a NPN transistor (PN100), emitter to ground, and collector is 12v + 1k resistor + LED, to start with.

The first problem is the LED never goes fully off.

If the output doesn't go below 0.5V the transistor will stay partially on of course, - easily fixed with a resistor, or diode + resistor.
If you get as far as trying the relay make sure there's a back emf protection diode across the relay coil.