Forum Home › Forums › Communicating with Devices › Modbus › How to send command to rs485 Relay board
- This topic has 36 replies, 3 voices, and was last updated 4 years, 2 months ago by hethongscada62.
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January 10, 2020 at 12:59 pm #6363manjey73Participant
This relay works on Modbus RTU, just the author tried to connect it first through an Ethernet – RS485 Converter and got confused.
- This reply was modified 4 years, 3 months ago by manjey73.
January 10, 2020 at 1:09 pm #6365hethongscada62ParticipantHi Mikhail,
Yes, that is a screenshot in the last time that it was configured Modbus TCP. There are some parameters bellow
1.Description:
R421A08 8 channel Modbus relay module equipped with mature and stable 8-bit MCU and RS485 level communication chip,adopt standard MODBUS RTU format RS485 communication protocol. It can realize 8bit input signal detection and 8bit relay output. It can be used for digital detection or power control occasions.
2.Features:
1>.Support Modbus RTU protocol
2>.Support RS485/TTL UART interface
3>.Output indicator in multi mode
4>.Address can be set
5>.Support input reverse connection protection
6>.Relay switch output
7>.Support parameter memory function
3.Parameters:
1>.Item name: 8CH Modbus Relay Module
2>.Work voltage:DC 12V
3>.Baud rate:9600bps
4>.Set address:0x01~0x3F
5>.Delay time: 0~255s
6>.Load: AC 250V 10A or DC 28V 10A
7>.Protocol:Modbus RTU
8>.Interface:RS485/TTL UART
9>.Control channel: 8channel
10>.Operating Temperature:-20℃~85℃
11>.Operating Humidity:5%~95%RH
12>.Module Size:90*62*19mm
I hope these parameters can help you and me in the further.
Thanks
Han HoangJanuary 10, 2020 at 1:44 pm #6366MikhailModeratorCould you send communication line log again? Resize the application window to show more information.
What converter do you use to connect the module to a computer?
January 10, 2020 at 2:00 pm #6367manjey73ParticipantWhere did you get this template ?
January 10, 2020 at 2:18 pm #6368hethongscada62ParticipantDear manjey73,
That template was created by me.
Thanks a lotJanuary 10, 2020 at 2:52 pm #6369hethongscada62ParticipantDear Mikhail,
What converter do you use to connect the module to a computer?
RS485-RS232-USB converter. This converter connects to a computer. The relay board R421A08 was tested by Modbus Poll – MbPoll1 using this converter. Send commands from Mbpoll1, the relay works perfectly. You can see the screenshot:
https://ibb.co/c67893j
Now connecting a converter to computer using Communicatore to send commands. Configurations were sent to you. The relay can not work. Some screenshots were taken again:
https://ibb.co/dKLFqHP
https://ibb.co/FWLkvG6
Thank you so much
Han HoangJanuary 10, 2020 at 6:43 pm #6372manjey73ParticipantWhy didn’t you use my template ? It is checked since I used this relay Board
can’t you see the difference between what ModbusPoll sends and yours ? ModbusPoll adds the calculated Checksum to the query. You do not add a binary command when you send it. The relay works with HoldingRegisters requests, you are trying to work with Coils
- This reply was modified 4 years, 3 months ago by manjey73.
January 10, 2020 at 6:50 pm #6374manjey73ParticipantOnce again I offer my template for this relay
In the Communicator, disable the binding to the Server (Bounds), download my template and start the Communicator
Check Request Modbus RTU from ModbusPoll
01 06 00 01 01 00 D9 9A
and other
- This reply was modified 4 years, 3 months ago by manjey73.
January 11, 2020 at 1:21 am #6376hethongscada62ParticipantDear manjey73,
Thank you so much. I was tried again to use your template. The result get better. The communication between communicator and relay board was set up. But the status of relay is not changed when i send the commands (standard, binary, string, hexdecimal). Some screenshot are bellowing:
https://ibb.co/prXbJ5g
https://ibb.co/d2H2G5M
https://ibb.co/DwgNpQz
https://ibb.co/Kxq8z0t
https://ibb.co/JcDhnGH
Where is wrong? I did not understand. Can you check it again?
Thank you again
Han HoangJanuary 11, 2020 at 6:52 am #6377manjey73Participanthttps://ibb.co/JcDhnGH – Here you send the string again
https://ibb.co/DwgNpQz – Here in the first two lines you can see that the line went to ASCII-31 character code 1, 20-the code of the space character
https://ibb.co/d2H2G5M – Here you are trying to send a command with the wrong CRC, try 01 06 00 01 02 00 D9 6A
January 11, 2020 at 6:56 am #6378manjey73ParticipantShow part of the log Communication Line State
Also try sending a Standard command, command number 1-8, value 256, 512 or 768
- This reply was modified 4 years, 3 months ago by manjey73.
January 11, 2020 at 10:32 am #6382hethongscada62ParticipantHi manjey. Because it did not work so I tried to test all types. Not at all
Thinking now.
Thank you againJanuary 11, 2020 at 12:16 pm #6383manjey73ParticipantSo you were able to turn on and off the relay ?
January 11, 2020 at 1:05 pm #6384hethongscada62ParticipantHi manjey.
Stil can not. Where is wrong i can not find.
Very triedJanuary 11, 2020 at 1:54 pm #6385hethongscada62ParticipantDear manjey73,
The problem was resolved. I can to control On-Off of relay now. The rapid Scada was great.
Thank you very much.
Han Hoang -
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