AM312 vs HC-SR505: Mini PIR Sensor Comparison Guide

Overview

Both the AM312 and HC-SR505 are miniaturized versions of the classic HC-SR501, designed for applications where board space is limited. They maintain similar functionality while significantly reducing physical footprint.

Technical Specifications Comparison

Parameter	AM312	HC-SR505
Dimensions	10mm × 8mm	12mm × 12mm
Operating Voltage	2.7V – 12V	4.5V – 20V
Operating Current	35µA (standby)	50µA (standby)
Output Voltage	3.0V (HIGH)	3.3V (HIGH)
Detection Range	3-5 meters	3-7 meters
Detection Angle	100°	120°
Delay Time	2 seconds (fixed)	3-5 seconds (fixed)
Operating Temp	-20°C to +60°C	-20°C to +80°C

Detailed Analysis

Size and Form Factor

The AM312 is notably smaller at just 10×8mm, making it ideal for ultra-compact wearables and discreet installations. The HC-SR505, while still considered “mini,” offers a slightly larger footprint that can be advantageous for hand-soldering and prototyping.

Power Consumption

For battery-powered applications, the AM312 has a clear advantage with its 35µA standby current, nearly 30% lower than the HC-SR505. This difference can translate to weeks of additional battery life in continuous-operation scenarios.

Voltage Range

The AM312’s wider voltage range (down to 2.7V) makes it compatible with 3.3V systems like ESP8266 and Raspberry Pi without level shifting. The HC-SR505 requires at least 4.5V, making it more suitable for traditional 5V Arduino projects.

Detection Performance

The HC-SR505 offers slightly better detection range (up to 7 meters vs 5 meters) and wider detection angle (120° vs 100°). This makes it preferable for room-scale monitoring applications where coverage area is critical.

Pinout Comparison

AM312 Pinout (3 pins):

• Pin 1: VCC (2.7-12V)
• Pin 2: GND
• Pin 3: OUT (digital output)

HC-SR505 Pinout (3 pins):

• Pin 1: VCC (4.5-20V)
• Pin 2: OUT
• Pin 3: GND

Note the different pin ordering! Always verify pinout before wiring.

Application Scenarios

Choose AM312 When:

• Building battery-powered IoT sensors
• Working with 3.3V logic microcontrollers
• Space is extremely limited (<10mm board space)
• Power efficiency is the primary concern
• Fixed 2-second delay works for your use case

Choose HC-SR505 When:

• Detection range is critical
• Working with 5V Arduino systems
• Need wider coverage angle
• Slightly longer delay (3-5s) is acceptable
• Mounting in locations where larger size isn’t an issue

Wiring Examples

AM312 with ESP8266 (3.3V)

// AM312 connected to ESP8266
int pirPin = D1;  // GPIO5

void setup() {
  pinMode(pirPin, INPUT);
  Serial.begin(115200);
}

void loop() {
  if (digitalRead(pirPin) == HIGH) {
    Serial.println("Motion detected!");
    // Add your IoT code here
  }
  delay(100);
}

HC-SR505 with Arduino (5V)

// HC-SR505 connected to Arduino Uno
int pirPin = 2;

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

void loop() {
  if (digitalRead(pirPin) == HIGH) {
    Serial.println("Motion detected!");
  }
  delay(200);
}