Overview

The HC-SR501 is an automatic pyroelectric infrared (PIR) motion sensor module based on the BISS0001 micro-power PIR processing IC. It detects motion by sensing changes in infrared radiation (heat) emitted by human bodies, animals, or objects passing across its field of view.

The module features a hemispherical white Fresnel lens that focuses IR radiation onto dual internal pyroelectric sensor elements. Onboard potentiometers allow users to adjust detection sensitivity (3 m to 7 m range) and output delay time (0.5 s to 300 s), while a jumper selects between single and repeatable trigger modes.

Quick reference

Supply voltage (VCC)4.5 V to 20.0 V DC (5 V nominal)
Output logic level3.3 V TTL (HIGH when motion detected, LOW when idle)
Quiescent current<50 μA< 50\text{ }\mu\text{A}
Sensing distanceAdjustable 3 m to 7 m
Sensing angle<120∘< 120^\circ cone angle
Delay timeAdjustable 0.5 s to 300 s
Trigger modeJumper-selectable: Non-repeatable (L) / Repeatable (H)

Pinout

Standard 3-Pin Header

PinNameTypeDescription
1VCCPowerSupply voltage (+4.5 V to +20.0 V DC)
2OUTDigital OutputMotion detection output (3.3 V HIGH on motion, 0 V LOW idle)
3GNDPowerGround (0 V)

Controls & Jumpers

  • Sensitivity Potentiometer (Sx / SENS): Turn clockwise to increase sensing distance (up to ~7 m); counter-clockwise to decrease (~3 m).
  • Delay Time Potentiometer (Tx / TIME): Turn clockwise to increase output pulse duration (up to 300 s); counter-clockwise to decrease (~0.5 s).
  • Trigger Mode Jumper (L / H):
    • H (Repeatable / Retriggerable): Output remains HIGH as long as continuous motion is detected within the delay period.
    • L (Single / Non-repeatable): Output goes HIGH for the set delay duration, then goes LOW regardless of ongoing motion.

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVCCV_{CC}4.55.020.0VDC
Output HIGH VoltageVOHV_{OH}—3.3—VMotion detected
Output LOW VoltageVOLV_{OL}—0.0—VIdle / no motion
Quiescent CurrentIQI_{Q}—5065µAVCC=5.0 VV_{CC} = 5.0\text{ V}
Detection Angleθ\theta——120°Cone angle with Fresnel lens
Detection Rangedd3—7mAdjustable via potentiometer
Output Delay Timetdt_d0.5—300sAdjustable via potentiometer
Inhibit / Block Timetblockt_{block}—2.5—sDead time between triggers

Wiring

HC-SR501 Pin→Microcontroller (Arduino / ESP32)Notes
VCC5V (or 4.5V–20V external supply)Onboard 3.3V LDO requires ≥4.5 V\ge 4.5\text{ V} input
OUTDigital Input Pin (e.g. GPIO4)3.3V TTL signal (safe for 3.3V ESP32 / Pi GPIO)
GNDGNDGround
Note

Warm-up / Initialization Period: Upon initial power-up, the HC-SR501 requires 30 to 60 seconds to calibrate to background thermal radiation. During this period, the output pin may toggle randomly 1 to 3 times. Ignore sensor readings during the first minute after powering on.

Common mistakes

  • Powering from 3.3V rail: The module contains an onboard 3.3V LDO regulator (e.g. 7133). Supplying 3.3V to VCC causes the regulator to drop out, producing erratic triggers or a completely non-responsive output. Always feed VCC with ≥4.5 V\ge 4.5\text{ V}.
  • Ignoring the 2.5-second block time: After outputting a LOW signal, the BISS0001 IC enforces a ~2.5 second inhibit time during which no motion can trigger the sensor. Rapid motion testing will appear to miss triggers.
  • Placing near heat / draft sources: Air conditioners, direct sunlight, heating vents, or high-power warm components can create thermal air currents that false-trigger PIR sensors.

Notes

  • The 3.3V output level makes the OUT signal directly compatible with 3.3V microcontrollers (ESP32, ESP8266, Raspberry Pi) without needing level shifters.

Assets & downloads