| Pin | Name | Function | |-----|------|-----------| | 1 | VCC | +5V DC (regulated) | | 2 | Trig | Trigger input (active high, 10 µs min pulse) | | 3 | Echo | Echo output (PWM width = time of flight) | | 4 | GND | Ground |
1. Overview & Key Differentiators The AJ-SR04M is an improved, industrial-grade variant of the popular HC-SR04. Unlike the standard HC-SR04, this module is enclosed in a waterproof, IP67-rated housing , making it suitable for outdoor, dusty, or humid environments (e.g., tank level sensing, outdoor robotics, car reverse sensors). aj sr04m datasheet
void loop() digitalWrite(TRIG, LOW); delayMicroseconds(2); digitalWrite(TRIG, HIGH); delayMicroseconds(10); digitalWrite(TRIG, LOW); | Pin | Name | Function | |-----|------|-----------|
AJ-SR04M is the best all-rounder for outdoor/wet applications needing short-range detection (2 cm blind zone). JSN-SR04T has longer range but larger blind zone (20 cm). HC-SR04 is indoor only. 10. Application Circuit & Code Examples 10.1 Arduino (Standard) #define TRIG 9 #define ECHO 10 void setup() Serial.begin(9600); pinMode(TRIG, OUTPUT); pinMode(ECHO, INPUT); sound speed changes with temperature:
delay(60);
// Add 1kΩ resistor from Echo to ESP32 pin, and 2kΩ from pin to GND. // Then code same as Arduino but use pulseIn() or interrupts. 10.3 Raspberry Pi (Python) import RPi.GPIO as GPIO import time GPIO.setmode(GPIO.BCM) TRIG = 23 ECHO = 24 GPIO.setup(TRIG, GPIO.OUT) GPIO.setup(ECHO, GPIO.IN)
For tank level sensing, ensure no obstructions inside the beam cone. For obstacle avoidance, mount multiple sensors to cover blind spots. 6. Temperature Compensation & Accuracy The datasheet specifies ±1% accuracy at 20°C. However, sound speed changes with temperature: