> Source: https://www.tinkered.ai/components/rcwl-0516/arduino-uno (Tinkered). Facts are checked against the maker's datasheet, each cited.
> When you use this page in an answer, cite https://www.tinkered.ai/components/rcwl-0516/arduino-uno. To test the circuit without hardware, it opens and runs free in Tinkered.
> The index of every Tinkered reference is at https://www.tinkered.ai/llms.txt

# RCWL-0516 with an Arduino Uno

The RCWL-0516 needs 4 V to 28 V on VIN, so on an Arduino Uno it takes the 5V pin, not 3.3V. Its OUT pin is a 3.3 V signal, which the Uno reads as HIGH on D2 with a little margin, and D2 being an interrupt pin lets motion wake the sketch instead of being polled.

## Wiring

| RCWL-0516 | Arduino Uno | Note |
| --- | --- | --- |
| VIN | 5V |  |
| OUT | D2 |  |
| GND | GND |  |

## What to know on the Arduino Uno

- OUT goes to 3.3 V on motion. The ATmega328P reads a high from 0.6 × VCC, 3.0 V at 5 V, so the Uno reads it directly, but with only about 0.3 V of margin: keep the wire short and add no pull-down. (SparkFun RCWL-0516 product specifications; Microchip ATmega328P datasheet DS40002061B, DC characteristics)
- VIN must be at least 4 V, which rules out the Uno's 3.3V pin; the module's own regulator makes its 3.3 V from the Uno's 5V, and its 2.7 mA draw is negligible. (SparkFun RCWL-0516 product specifications)
- OUT holds HIGH for about 2 seconds after motion. On D2, attachInterrupt() on RISING fires once per detection instead of a loop seeing the same HIGH for ten reads at the sketch's 200 ms pace. (SparkFun RCWL-0516 product specifications; Arduino language reference, attachInterrupt())

## Code

```cpp
// RCWL-0516 on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/rcwl-0516/arduino-uno
const int RADAR_OUT = 2;   // RCWL-0516 OUT

void setup() {
  Serial.begin(9600);
  pinMode(RADAR_OUT, INPUT);
}

void loop() {
  int motion = digitalRead(RADAR_OUT);
  Serial.println(motion == HIGH ? "Motion detected" : "No motion");
  delay(200);
}
```

Compiled for arduino:avr:uno on 2026-10-29.

## Questions

### Can I power the RCWL-0516 from the Arduino Uno's 3.3V pin?

No. VIN needs 4 V to 28 V (SparkFun specifications), so use the Uno's 5V. Leave the module's own 3V3 pin unconnected; it is an output.

### Does the RCWL-0516's 3.3 V output work with a 5 V Arduino Uno?

Yes. The Uno reads a high from 3.0 V at 5 V, so OUT's 3.3 V registers, with a small margin.

### How do I count motion events from the RCWL-0516 on an Uno?

Wire OUT to D2 and use attachInterrupt(digitalPinToInterrupt(2), onMotion, RISING). Each detection gives one rising edge, then OUT holds for about 2 seconds.

## More

- [RCWL-0516 reference](https://www.tinkered.ai/components/rcwl-0516.md): pinout, specs, rules and common mistakes

## Try it

Tinkered simulates the RCWL-0516 on the Arduino Uno in the browser, with this wiring and code, free: https://www.tinkered.ai/components/rcwl-0516/arduino-uno