1. Product Overview
The eletechsup N4DSB03 is a dual-channel RS485 DS18B20 adapter board designed for collecting temperature data. It can simultaneously acquire temperature readings from two DS18B20 sensors and convert them into MODBUS RTU format. This module is suitable for applications such as PLC analog IO expansion, thermostat systems, and smart home integrations.
2. Specifications
| Feature | Specification |
|---|---|
| Working Voltage | DC 6-25V (with reverse polarity protection) |
| Working Current | 6-7mA |
| Acquisition Channels | 2 channels |
| Protocol | MODBUS RTU (03, 04 read commands; 06, 16 write commands) |
| Serial Port Baud Rate | 9600 (default), configurable from 1200-115200, N, 8, 1 |
| Cascading Capacity | Up to 247 modules (R485 repeater recommended for more than 16 modules) |
| Adapted Sensor | DS18B20 Temperature Sensor |
| Temperature Measurement Range | -55°C to +125°C (-67°F to +257°F) |
| Module Dimensions (No terminal) | 32.6 X 25.8 X 3.5MM |
| Module Dimensions (With terminal) | 32.6 X 25.8 X 12MM |
| Module Weight (No terminal) | 3.6g |
| Module Weight (With terminal) | 7.6g |
| Output Current | 8MA |
| Output Frequency | 1 |
| Output Power | 1 - 50W |
| Output Type | DUAL |
3. Pin Description
Refer to the module layout image for visual identification of pins.
Image: N4DSB03 Module Layout with Labeled Components (Channels, Power, RS485, RES jumper)
- VCC: Positive power supply input (DC 6-25V)
- GND: Negative power supply input
- A+: RS485 A+ data line
- B-: RS485 B- data line
- CH1 DS18B20 Connections:
- GND: DS18B20 negative power supply
- D1: DS18B20 DATA line for Channel 1
- 5V: DS18B20 positive power supply for Channel 1
- CH2 DS18B20 Connections:
- GND: DS18B20 negative power supply
- D2: DS18B20 DATA line for Channel 2
- 5V: DS18B20 positive power supply for Channel 2
4. Setup and Wiring
Careful wiring is crucial for proper operation. Ensure all connections are secure and correctly polarized.
4.1 DS18B20 Sensor Connection
Connect your DS18B20 temperature sensors to the respective channels (CH1 and CH2) on the N4DSB03 module. The recommended lead length for the DS18B20 sensor is within 15 meters.
Image: DS18B20 Temperature Sensor with Wire Details (DATA, VCC, GND)
4.2 Power Supply Connection
Connect a DC power supply within the 6-25V range to the VCC and GND terminals of the module. The module features reverse polarity protection.
4.3 RS485 Bus Connection
Connect the RS485 A+ and B- lines from your master device (e.g., PC via USB to RS485 converter, PLC, TP) to the A+ and B- terminals on the N4DSB03 module. The recommended RS485 bus length is within 100 meters.
4.4 Wiring Diagrams
Below are detailed wiring diagrams for single and dual-channel configurations, as well as a multi-module bus setup.
Image: Wiring Diagram for Single Channel DS18B20 and RS485. Shows connections for one DS18B20 sensor to Channel 1 (GND, D1, 5V) and RS485 (A+, B-) to a DC 6-25V power source. Recommended DS18B20 lead length is within 15 meters, and RS485 bus length is within 100 meters.
Image: Wiring Diagram for Dual Channel DS18B20 and RS485. Illustrates connections for two DS18B20 sensors to Channel 1 (GND, D1, 5V) and Channel 2 (GND, D2, 5V), with RS485 (A+, B-) connected to a DC 6-25V power source. Lead length recommendations remain the same.
Image: RS485 Bus Connection Diagram with Multiple N4DSB03 Modules. Shows how multiple N4DSB03 modules can be connected to a single RS485 bus, allowing up to 32 modules and 64 temperature measurement points. A USB to RS485 converter (UD48501) is shown connecting to a PC, PLC, or TP.
5. Operating Instructions
The N4DSB03 module communicates using the MODBUS RTU protocol. It supports standard MODBUS functions for reading and writing data.
- Read Commands: Use MODBUS function codes 03 and 04 to read temperature data from the connected DS18B20 sensors.
- Write Commands: Use MODBUS function codes 06 and 16 for writing configurations or control signals, if applicable.
- Baud Rate: The default serial port baud rate is 9600. Ensure your master device is configured to match the module's baud rate. It can be adjusted from 1200 to 115200.
- RS485 Address: Each module on an RS485 bus must have a unique address. By modifying the RS485 address, up to 247 modules can be cascaded. For systems with more than 16 modules, an R485 repeater is recommended to maintain signal integrity.
6. Maintenance
The N4DSB03 module is designed for reliable operation with minimal maintenance. Keep the module clean and free from dust and moisture. Ensure proper ventilation if installed in an enclosure.
7. Troubleshooting
7.1 Communication Failure
If you experience communication failures or unexpected behavior, try the following:
- Check Wiring: Verify all power, DS18B20, and RS485 connections are correct and secure.
- Baud Rate Mismatch: Ensure the baud rate of your master device matches the module's configured baud rate.
- RS485 Address Conflict: Confirm that each module on the bus has a unique RS485 address.
- Restore Factory Settings: If communication issues persist, you can restore the module to its factory default settings. To do this, short the RES jumper on the board for 5 seconds. Refer to the module layout image in Section 3 for the location of the RES jumper.
8. User Tips
Based on common inquiries and usage patterns:
- Software Integration: For advanced users, integrating the MODBUS RTU protocol with custom software or existing PLC systems requires knowledge of MODBUS addressing and function codes. Consult MODBUS documentation for detailed protocol information.
- Sensor Placement: For accurate temperature readings, ensure DS18B20 sensors are placed in locations representative of the temperature you wish to measure and are protected from direct heat sources or drafts that could skew readings.
9. Warranty and Support
For technical support, troubleshooting assistance beyond this manual, or warranty inquiries, please contact eletechsup customer service through your purchase platform. Provide your product model (N4DSB03) and a detailed description of the issue for faster resolution.
