RCWL-0516 Microwave Radar Motion Sensor
Microwave radar motion sensor that detects movement through walls, glass, and plastic enclosures.
A microwave Doppler sensor that detects motion through glass and thin plastic, often used where PIR sensors are blocked by enclosures.
Specifications
| Sensor type | RF microwave Doppler radar, operating at 3.18 GHz (unlicensed ISM band) |
| Detection range | ~5-9 meters, depending on target size and PCB antenna orientation |
| Operating voltage | 4V–28V DC input, with an onboard regulator providing a 3.3V rail (~100mA available) for external use |
| Output | 3.3V digital HIGH on the OUT pin while motion is detected |
| Output hold time | ~2 seconds by default after last detected motion, adjustable by modifying the onboard Cds/R-GN solder pads |
| Penetration | Passes through non-metallic materials — glass, thin plastic, drywall — unlike PIR sensors, which these materials block |
| Power draw | Continuously transmitting RF — not a low-power sensor; no sleep state like PIR modules have |
| Interface | Digital output (OUT) — simple HIGH/LOW read, no bus protocol |
Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | VIN | Power input, 4-28V DC |
| 2 | GND | Ground |
| 3 | 3V3 | Onboard 3.3V regulator output — usable to power other low-current logic, not just an input |
| 4 | OUT | Motion detection output, 3.3V HIGH while triggered |
| 5 | CDS | Light-sensitivity gate input — pairs with an external photoresistor to disable detection above a chosen light level (often left unconnected) |
This sensor never sleeps — unlike PIR, it's continuously emitting and listening for RF reflections, so it draws power the whole time it's on. Avoid it for battery-only, low-power designs; PIR is dramatically more efficient for that use case.
Keep metal away from the antenna trace — the sensing element is a PCB trace acting as an antenna. Nearby metal enclosures, wires bundled too close, or even a metal screw near the board can detune it, causing false triggers, reduced range, or a sensor that never stops reporting motion. Give it several cm of clearance from metal on all sides where possible.
Hold time is fixed on stock boards — the ~2 second output-hold behavior after motion stops is set by an onboard resistor/capacitor pair (labeled R-GN / Cds pads on most boards). Changing it requires a physical component swap, not a software setting.
CDS pin is optional — if you want the sensor to only report motion in darkness (e.g., a nightlight trigger), wire a photoresistor to the CDS pad per the module's silkscreen; most projects leave this pin unconnected and it works fine at full sensitivity regardless of ambient light.
Variants
Choose the RCWL-0516 specifically when the sensor has to be hidden behind a sealed enclosure, glass panel, or thin plastic wall — that's the one scenario a PIR sensor can't handle. If the sensor sits in open air with a clear view of the room, the HC-SR501 PIR is usually the better default: it's less prone to false triggers from things like curtains, fans, or nearby metal objects vibrating.
| Variant | Temp range | Hum range | Accuracy | Protocol | Price |
|---|---|---|---|---|---|
| RCWL-0516 | ~$1-2 | ||||
| HC-SR501 (PIR) | ~$1-3 |