AJ-SR04M Reversing Radar Waterproof Ultrasonic Ranging Module K02

AJ-SR04M is a waterproof ultrasonic ranging module designed with an integrated transceiver. It offers reliable distance measurement for various applications. It's compatible with HC-SR04 software.

Features

• 3-5V Power Supply
• Waterproof, suitable for harsh environments
• Ultra-low standby current
• 5 output modes
• 20cm minimum blind zone
• 20cm-450cm wide measurement range (flat surface)
• High resolution
• Operating temperature: -20°C - 80°C

Applications

• Smart car obstacle avoidance
• Object distance measurement, human height measurement
• Quadcopter altitude hold and obstacle avoidance
• Intelligent traffic control, parking space display

Performance Parameters

Interface Definition

Mode Selection

• Mode 1: Normal pulse waveform, minimum consumption 5mA
• Mode 2: Low power pulse waveform, minimum consumption 10uA
• Mode 3: Automatic serial port, minimum consumption 6.5mA
• Mode 4: Serial port trigger, minimum consumption 7uA
• Mode 5: ASCII code output, minimum consumption 7uA

Extended Range 6-7M Adjustment:

1. Replace with low residual vibration probe
2. Modify the following image to increase the gain resistance 124 -> 224

Measurement Operation:

(See images for Mode 1, Mode 2, Mode 3, Mode 4 and Mode 5 timing diagrams and explanations)

Mode 1 Timing

• Working Principle:

  Compatible with HC-SR04. Give the Trig pin a >10us high-level trigger signal, and the module will work once. The corresponding Echo pin will output a high level, and the duration of the high level is the distance from the module to the obstacle. Distance = high level time * sound speed / 2;

Mode 2 Timing

• Working Principle:

  Give the Trig pin a >100us high-level trigger signal, and the module will work once. The corresponding Echo pin will output a high level, and the duration of the high level is the distance from the module to the obstacle. Distance = high level time * sound speed / 2;

Mode 3 Timing

• Working Principle:

  The module automatically outputs a frame every 100ms, containing 4 8-bit data. The frame format is: 0XFF+H_DATA+L_DATA+SUM (Baud rate is set to 9600, none, 8bit, 1stop)

  1. 0XFF: Start of frame, used for judgment.
  2. H_DATA: High 8 bits of distance data
  3. L_DATA: Low 8 bits of distance data
  4. SUM: Data sum, used for verification. H_DATA+L_DATA=SUM (only low 8 bits).
  5. H_DATA and L_DATA constitute 16-bit data, which is the distance value in millimeters.

  Example Product Response: FF 07 A1 A7

  Checksum SUM=A8=(0x07+0xA1)&0x00ff

  0x07 is the high bit of the distance: 0xA1 is the low bit of the distance

  Distance value 0x07A1: Convert to decimal to get 1953: Unit is millimeters

Mode 4 Timing

• Working Principle:

  Send one of 11 data to the RX pin or set the RX pin low once, and the module will measure after triggering. It will output a frame of data, containing 4 8-bit data. The frame format is: 0XFF+H_DATA+L_DATA+SUM. Baud rate setting 9600, none, 8bit, 1stop

  1. 0XFF: Start of a frame of data, used to determine.
  2. H_DATA: The high 8 bits of the distance data.
  3. L_DATA: The low 8 bits of the distance data.
  4. SUM: Data and, for verification, H_DATA+L_DATA=SUM (only low 8 bits).
  5. H_DATA and L_DATA constitute 16-bit data, which is the distance value in millimeters.

  Example Product Response: FF 07 A1 A7

  Checksum SUM=A8=(0x07+0xA1)&0x00ff

  0x07 is the high bit of the distance data

  0xA1 is the low bit of distance data

  The distance value is 0x07A1: convert to decimal to 1953: unit is millimeters

Mode 5 Timing

• Working Principle:

  Mode 5 is the same as Mode 4, except that the output format of Mode 5 is ASCII code. The distance value can be directly displayed in the serial port software.

Module Workflow Diagram

(See image "68bfde39c9115f823c5d9c85" for module workflow)

• Module Power On
• Module Self-Check
• Check R27 Resistance Value to Determine Startup Mode
  • R27=open: Pulse Width Output Mode
  • R27=47K: Automatic Serial Port Mode
  • R27=120K: Trigger Serial Port Mode