NT18B07: 7 Kanal RS485 Temperatur Sensor with Modbus RTU

The NT18B07 is a 7-channel NTC temperature sensor interface board/module that uses the MODBUS RTU communication protocol over an RS485 interface for industrial and automation applications. Requires external B3950 10K 1% NTC thermistors

NT18B07 Description

• Operating current ranges from 8 to 13 mA, depending on external connections.
• The device supports MODBUS RTU commands using function codes 03 and 06.
• By adjusting the R485 address, up to 247 modules can be cascaded; if exceeding 16, an R485 repeater is recommended.
• A maximum of 8 temperature sensors can be connected at once.
• Temperature measurement spans from -55°C to +125°C (-67°F to +257°F), with an accuracy of ±0.5°C between -10°C and 85°C.
• Resistance value: 10K
• Resistance accuracy: ±1%
• Resistance B value: 3950 ±1%
• Wire specification: 2651 26# parallel resistance, temperature resistance 105°C
• Connector model: XH2.54-2P
• Probe: without mounting holes
• Supply voltage: 6-24V

• Product type: NTC 10K / B3590 1%
• Temperature range: -50°C to 125°C (-58°F to 257°F)

Default settings: SlaveID: 1, 9600 baud, parity: N,8,1

The NT18B07 is a 7-channel NTC thermistor temperature acquisition module that communicates via RS485 Modbus RTU. Unlike the MAX31865 (which is SPI-based), the NT18B07 requires an RS-485-to-TTL converter (e.g., a MAX485 module) to interface with an Arduino.

Wiring Diagram

To connect the NT18B07 to an Arduino Uno using a standard MAX485 module:

• NT18B07 A+ to MAX485 A and NT18B07 B- to MAX485 B.
• MAX485 VCC/GND: 5V and GND.
• MAX485 RO: Arduino Pin 2 (RX).
• MAX485 DI: Arduino Pin 3 (TX).
• MAX485 DE & RE: Tied together to Arduino Pin 4 (Direction Control).
• NT18B07 Power: DC 6V–24V.

Arduino Example Code

This code uses the ModbusMaster library to read temperatures from the first 7 channels.

#include <ModbusMaster.h>
#include <SoftwareSerial.h>
 
#define MAX485_RE_DE 4
SoftwareSerial rs485(2, 3); // RX, TX
 
ModbusMaster node;
 
void preTransmission() { digitalWrite(MAX485_RE_DE, 1); }
void postTransmission() { digitalWrite(MAX485_RE_DE, 0); }
 
void setup() {
  pinMode(MAX485_RE_DE, OUTPUT);
  digitalWrite(MAX485_RE_DE, 0);
 
  Serial.begin(9600);
  rs485.begin(9600); // Default NT18B07 baud rate
 
  node.begin(1, rs485); // Default Slave ID is 1
  node.preTransmission(preTransmission);
  node.postTransmission(postTransmission);
}
 
void loop() {
  // Read 7 registers starting at 0x0000 (Channels 1-7)
  uint8_t result = node.readHoldingRegisters(0x0000, 7);
 
  if (result == node.ku8MBSuccess) {
    for (int i = 0; i < 7; i++) {
      int16_t rawTemp = node.getResponseBuffer(i);
      // Temperature is stored as raw value x 10. Handle negative values.
      float celsius = (rawTemp > 32767) ? (rawTemp - 65536) / 10.0 : rawTemp / 10.0;
      Serial.print("CH"); Serial.print(i+1);
      Serial.print(": "); Serial.print(celsius); Serial.println(" C");
    }
  } else {
    Serial.print("Modbus Error: 0x"); Serial.println(result, HEX);
  }
  delay(2000);
}

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