Overview

The HC-SR505 is a miniature automatic-sensing passive infrared (PIR) motion detector module. Featuring a slim cylindrical Fresnel lens cap mounted on a narrow 40 mm×10 mm40\text{ mm} \times 10\text{ mm} PCB, it provides reliable human presence detection across a 100∘100^\circ cone up to 3 meters3\text{ meters}.

Operating across a wide supply voltage range (4.5V4.5\text{V} to 20.0V20.0\text{V} DC), the HC-SR505 includes internal automatic re-triggering logic: as long as motion continues within range, the 3.3V digital output (OUT) remains held High. Once motion ceases, OUT returns Low after a fixed 8-second delay.

Quick reference

Operating voltage (VCC)4.5 V to 20.0 V DC (5.0 V nominal)
Quiescent current<60 μA< 60\ \mu\text{A} static idle
Detection distanceUp to 3.0 meters (10 feet10\text{ feet})
Detection angle<100∘< 100^\circ cone angle
Output logic level3.3V Active-High (3.3V3.3\text{V} High during motion, 0V0\text{V} Low idle)
Output delay time (tdelayt_{delay})~8.0 seconds (±30%\pm 30\%) automatic repeatable delay
Form factorCylindrical lens diameter 10 mm10\text{ mm}, total module length 40 mm40\text{ mm}

Pinout

Standard 3-pin 0.1" (2.54 mm) header:

PinNameTypeDescription
1 (+)VCCPowerPower supply input (+4.5 V to +20.0 V DC)
2 (OUT)OUTDigital OutputActive-High digital output (3.3V logic HIGH during motion)
3 (-)GNDPowerGround reference (0 V)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVCCV_{CC}4.55.020.0VDC
Quiescent CurrentIstaticI_{static}—5060µAIdle state
Output High LevelVOHV_{OH}3.03.33.6VMotion detected
Output Low LevelVOLV_{OL}0.00.00.2VNo motion
Motion Hold Delaytdelayt_{delay}6.08.010.0sRepeatable trigger hold time
Lens DiameterDialensDia_{lens}—10.0—mmCylindrical white Fresnel lens

Automatic Repeatable Triggering Mode

Unlike older modules with manual jumper selects, the HC-SR505 operates strictly in automatic repeatable trigger mode:

  • If motion is detected at second 0, OUT goes High (3.3V).
  • If additional motion is detected at second 4, the 8-second internal timer resets automatically.
  • OUT remains High until 8 seconds after the LAST detected movement.

Wiring

HC-SR505 Pin→Arduino UnoESP32Notes
VCC (+)5V5VRequires ≥4.5V\ge 4.5\text{V} input
OUTDigital D2GPIO 43.3V logic output (safe for ESP32)
GND (-)GNDGNDSystem ground
Warning

Minimum 4.5V Supply Requirement:

  • Unlike the AM312 (which operates down to 2.7V), the HC-SR505 internal voltage regulator requires at least 4.5V on VCC. Supplying 3.3V to VCC causes continuous false triggering or complete failure to detect motion.

Example

cpp
const int pirPin = 2;
const int ledPin = 13;

void setup() {
  Serial.begin(9600);
  pinMode(pirPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  int pirState = digitalRead(pirPin);

  if (pirState == HIGH) {
    digitalWrite(ledPin, HIGH);
    Serial.println("MOTION DETECTED (HC-SR505)");
  } else {
    digitalWrite(ledPin, LOW);
  }

  delay(200);
}

Common mistakes

  • Powering from 3.3V rails: Always power HC-SR505 from a 5V (or higher) power rail.
  • Mounting behind glass: Pyroelectric infrared sensors cannot detect thermal IR through glass windows, as glass reflects/absorbs long-wave infrared radiation (9.4 μm9.4\ \mu\text{m}).

Notes

  • HC-SR505 vs HC-SR501: HC-SR505 is significantly smaller, lacks manual adjustment potentiometers, and features a fixed 8-second delay time.

Assets & downloads