HC-SR505 Mini PIR Motion Sensor Infrared Detector Module

The HC-SR505 outputs a digital 3.3V TTL high signal when motion is detected and 0V when idle. This makes it directly compatible with 3.3V logic microcontrollers like ESP32 or Raspberry Pi. For 5V systems like most Arduinos, the 3.3V signal is generally safe to read as a HIGH input, but a simple voltage divider or level shifter can be used for guaranteed compatibility.

The default delay time is fixed at approximately 8 seconds (±30%) and is not user-adjustable via onboard potentiometers like some larger PIR modules. The timing is controlled by the internal CMOS chip. For custom timing requirements, you would need to manage the output signal duration in your microcontroller code, ignoring the module's built-in delay, or source a variant specifically designed for adjustable delay.

Connect the module's three pins: VCC to your power source (4.5V-20V, often 5V from Arduino), GND to common ground, and the OUT pin to a digital input pin on the Arduino (e.g., D2). Since the output is 3.3V, it is typically safe to connect directly to an Arduino's digital pin. Monitor the chosen pin; a reading of HIGH indicates detected motion. Ensure your code accounts for the sensor's built-in output delay.

The HC-SR505 is configured in repeatable trigger mode by default. In this mode, when motion is detected, the output goes high and starts a delay timer. If another motion is detected within that delay period, the timer resets, extending the high output. This ensures continuous activation during ongoing activity. A non-repeatable mode would output a high pulse for the fixed delay period regardless of subsequent motion, requiring motion to stop completely before a new trigger can occur.