Arduino Human Infrared Sensor
Blue - Ground, connect to Arduino GND
Brown - Power, connect to external 12V source.
Red - 12 V output. Connect via a diode to arduino input pin. Enable pullup on arduino pin.

This way when the sensor output is low it will pull the arduino pin low. When the output is high the diode blocks the 12V from frying the arduino while the internal pullup ensures the input pin goes to a safe voltage for a high pin.

Don't put the diode the wrong way around or things will go bang.







simulate this circuit &ndash; Schematic created using CircuitLab