RCWL-0516 is a radar sensor which is used for motion detection, just like PIR motion sensor. But unlike PIR motion sensor, instead of sniffing the black body radiation from a moving person, this sensor uses a “microwave Doppler radar” technique to detect moving objects. That's why it is much more effective and precise than the PIR sensor.
Unlike the PIR motion sensor it can detect object all around it (360 degree). And as it is based on microwave, the signal can penetrate through walls.
When motion is detected, its "OUT" pin will switch from LOW (0 V) to HIGH (3.3 V) for a finite timebefore returning to its idle (LOW) state.
Supply Voltage: 4–28 VDC (tested with 5 V)
Operating frequency: ~3.2 GHz
Transmit power: 20 mW (typical)/30 mW (max)
Sensing Distance: 5–7 m
CDS — Sensor disable input (low = disable)
VIN — 4- to 28-V DC supply input
OUT — HIGH (3.3 V) motion detected/LOW (0 V) idle
GND — Ground/0 V
3V3 — Regulated DC output (100 mA max)
Applications: burglar alarm, automatic staircase light and other motion sensor based projects.