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Freigegebene technische Dokumentation veröffentlicht; Text-only und noindex

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'''Documentation notice:''' This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.

== Summary ==
Concise technical guide for the Waveshare Modbus RTU 8-channel relay module with RS485 bus, V3 protocol, and safety guidelines.

== Related products at JW Tech ==
* [https://shop.jw-tech.eu/p/WSAL17658 WSAL17658 – Industrial Modbus RTU 8-ch Relay Module with RS485 Interface, Multi Isolation Protection Circuits, 5V Power Supply]
* [https://shop.jw-tech.eu/p/WSAL25739 WSAL25739 – Industrial Modbus RTU 8-ch Relay Module (B) with RS485 Interface, Multi Isolation Protection Circuits, 7~36V Power Supply]

== Technical overview ==
* The module provides 8 relay channels over an RS485 interface using the Modbus RTU protocol.
* Two variants exist: WSAL17658 with a 5 V power supply and WSAL25739 (variant B) with a 7–36 V power supply.
* From September 2024, the V3 development protocol is used; it is backward compatible with V2 and adds new features.
* The serial interface uses standard parameters: 9600 baud, 8 data bits, no parity.
* For computer interfacing, SSCOM can send hex commands with Modbus CRC16 checksum, or Modbus Poll can read/write relay states.
* Demo environments are described for Raspberry Pi, STM32 (NUCLEO-F103RB), Arduino (UNO PLUS), and PLC (SIMATIC S7-200 SMART).
* RS485 must not be connected directly to a Raspberry Pi serial port; an RS485 level converter or the corresponding HAT/shield module is required.
* The relay environmental specification is -15 °C to +70 °C at 40–85 % relative humidity.

'''Commands and examples – verify before use:'''
<syntaxhighlight lang="text">
sudo raspi-config
sudo reboot
enable_uart=1
#dtoverlay=pi3-miniuart-bt
sudo apt-get install unzip
wget https://files.waveshare.com/wiki/Modbus-RTU-Relay/Modbus_RTU_Relay_Code.zip
unzip Modbus_RTU_Relay_Code.zip
cd Modbus_RTU_Relay_Code/Python3
sudo python3 main.py
</syntaxhighlight>

== Notes and version constraints ==
* All statements regarding compatibility, electrical values, commands, prices, stock, certifications, warranty, or safety require confirmation by a qualified professional, as they may be version-sensitive.
* The exact register addresses and function codes of the V3 protocol are only listed as headings in the source; concrete values are missing from the provided text.
* The 'Development Protocol V3' section contains no complete tables or command examples in the excerpt; these must be supplemented from the original source.
* Command formats such as 'Control Single Relay' or 'Set Baudrate Command' appear only as topic headings in the source; exact byte sequences are not included here.
* Power consumption figures (0.18 W standby / 2.9 W active at 5 V) refer to the 5 V variant; no comparable figures are available for the 7–36 V variant.

== Source and revision record ==
* [https://www.waveshare.com/wiki/Modbus_RTU_Relay Modbus RTU Relay - Waveshare Wiki]
* Source revision: 107667
* Captured: 2026-08-31T04:28:43+00:00
* SHA-256: <code>6511a0398311bf916805f224a92ffef4268876b19c222d34788c6e7dd9a36863</code>

WSAL17658 – Modbus RTU Relay/en - Versionsgeschichte

JWTechPublisher: Freigegebene technische Dokumentation veröffentlicht; Text-only und noindex