DFRobot URM15 75kHz Ultrasonic Sensor 30–500cm RS485

The URM15 uses the RS485 physical layer and communicates via the Modbus-RTU protocol. To connect it to an Arduino, you will need an RS485 to TTL/UART converter shield or module (e.g., MAX485). Connect the sensor's A and B lines to the converter, and the converter's RO and DI pins to the Arduino's serial RX and TX pins respectively. Use a Modbus library, such as ModbusMaster, to read distance registers (typically 0x0000).

The sensor has an internal temperature sensor for basic compensation. For higher accuracy in environments with rapid or extreme temperature gradients (e.g., near industrial ovens or in outdoor weather), you should enable external compensation mode. In this mode, you connect a separate, high-accuracy temperature sensor (like a DS18B20) to the designated input pins, and the URM15 uses this real-time data to calculate the precise speed of sound for its distance measurements.

Yes, you can daisy-chain multiple URM15 sensors on a single RS485 bus. Each sensor must be configured with a unique slave address (from 1 to 247) using the provided configuration commands over Modbus. Ensure the total bus length adheres to RS485 standards (up to 1200 meters at lower baud rates) and terminate the bus with a 120-ohm resistor at the farthest sensor to prevent signal reflections.

The sensor operates from a 5-12V DC supply. Exceeding 12V DC risks damaging the internal voltage regulator and circuitry. Always ensure your power source is stable and within this range. The sensor draws a maximum instantaneous current of 350mA during the ultrasonic pulse transmission; your power supply should be capable of providing this peak current.