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product url - Integrated Ultrasonic Proximity Sensor, Reversing radar, SR04T

Board Map, Dimension, Pins, chip info, Use Guide, Setup Jumper, etc.

The integrated ultrasonic proximity module provides non-contact distance sensing from 20 cm to 600 cm. The module integrates a transmitter/receiver transducer and control circuitry. The separate probe includes a 2.5 m cable.

Specifications

  • Supply voltage: DC 3.0–5.5 V
  • Operating current: < 8 mA
  • Probe frequency: 40 kHz
  • Maximum range: 600 cm
  • Minimum range: 20 cm
  • Long-range accuracy: ±1 cm
  • Resolution: 1 mm
  • Measurement angle: 75°

Inputs / Outputs

  • Trigger input:
    1. TTL pulse ≥ 10 µs
    2. Serial command 0x355
  • Echo output: pulse-width output (TTL)

Pins / Wiring

  • VCC: 3–5.5 V (power)
  • TRIG: trigger / control input
  • RX / ECHO: echo / output
  • TX: serial transmit (if applicable)
  • GND: ground (power negative)

Mechanical & Environmental

  • Dimensions: L 42 × W 29 × H 12 mm
  • Operating temperature: -20 °C to +70 °C
  • PCB color: blue

Pin Description

  • VCC: Power (positive)
  • TRIG / RX: Trigger input (send a high pulse ≥ 10 µs to start a measurement) / UART RX (receive)
  • ECHO / TX: Echo output — outputs a high pulse when a measurement completes; pulse width equals the ultrasonic round-trip time / UART TX (transmit)
  • GND: Ground (power negative)

Usage and Operating Modes

This module supports three selectable operating modes. Change the R27 resistor configuration to select a mode.

Mode 1 — Pulse/Trigger mode (R27 = open / no resistor soldered)

  1. Operation

    • Use the TRIG pin to trigger a measurement: apply a high pulse of at least 10 µs.
    • The module will automatically transmit 8 cycles of 40 kHz and listen for an echo.
    • When an echo is detected, the ECHO pin goes high; the high pulse duration equals the round-trip time of the ultrasonic signal.
    • Distance = (high_time × speed_of_sound) / 2 (speed_of_sound ≈ 340 m/s).
    • If no echo is received (out of range or probe not aimed at the target), the ECHO pin will automatically go low after 60 ms to indicate measurement end.
    • LED indicator: the LED is not a power indicator. It lights only when the module receives a trigger and is actively measuring.

  2. Timing diagram

Mode 2 — Auto-UART output (R27 = 47 kΩ soldered)

  • The module continuously outputs distance measurements over TTL serial at a 100 ms interval. Units: mm.
  • Serial settings: 9600, N, 8, 1.

Mode 3 — Command-triggered UART (R27 = 120 kΩ soldered)

  • On power-up the module enters standby and outputs TTL serial at 9600, N, 8, 1.
  • When the RX pin receives the command 0x55, the module performs a single measurement and sends a data frame on TX.
  • Frame format: 0xFF, H_DATA, L_DATA, SUM (4 bytes), where H_DATA and L_DATA contain the measured distance.

Operation (Modes 1–5)

Mode 1 — HC-SR04 compatible trigger mode

  • Trigger: apply a TRIG pulse > 10 µs.
  • Behavior: the module performs one measurement; the ECHO pin outputs a high pulse whose duration equals the ultrasonic round-trip time.
  • Distance calculation: distance = (ECHO_high_time × speed_of_sound) / 2 (speed ≈ 340 m/s).
  • Typical current (active average): ~6 mA.

Mode 2 — Low-power trigger mode

  • Trigger: apply a TRIG pulse > 100 µs.
  • Behavior: the module performs one measurement; ECHO outputs a high pulse while measuring. Distance is calculated the same way as Mode 1.
  • Standby current: ~10 µA.

Mode 3 — Auto periodic UART output

  • The module automatically sends a data frame every 100 ms over TTL serial.
  • Serial settings: 9600, N, 8, 1.
  • Frame format (4 bytes): 0xFF, H_DATA, L_DATA, SUM
    • 0xFF: start byte
    • H_DATA: high 8 bits of distance
    • L_DATA: low 8 bits of distance
    • SUM: checksum = (H_DATA + L_DATA) & 0xFF
  • Distance = (H_DATA << 8) | L_DATA (unit: mm).

Example

  • Example frame: 0xFF 0x07 0xA1 0xA8
    • H_DATA = 0x07, L_DATA = 0xA1
    • Checksum SUM = (0x07 + 0xA1) & 0xFF = 0xA8
    • Distance = 0x07A1 = 1953 mm
  • Typical current (active average): ~6.5 mA.

Mode 4 — Command-triggered UART / RX-trigger

  • Trigger: send a serial byte to RX or pull RX low once to start a single measurement.
  • After measurement the module outputs one data frame on TX using the same 4-byte format as Mode 3 (0xFF, H_DATA, L_DATA, SUM).
  • Serial settings: 9600, N, 8, 1.
  • Standby current: ~7 µA.

Mode 5 — ASCII serial output

  • Same trigger mechanism as Mode 4; the difference is the output format: ASCII text (human-readable) so distance can be displayed directly in serial terminal software.
  • Standby current: ~7 µA.

Applications, category, tags, etc.

Demo Code and Video

ref

Table of Contents

https://www.electrodragon.com