Unable to connect Mitsubishi FX-3U PLC FX3U-485-MB To MPPT(Charge Controller) through MODBUS

[praty 0]

I am using Mitsubishi FX3u series plc with FX3u-485ADP-MB serial communicator.Now I have connect my PLC with serial communucator to MPPT Charge Controller through RS485.  I have looped Ra to Sa and Rb to Sb took two wire to Mppt. The basic operation would be like PLC will be working as Master and Mppt as slave, Plc will read and write the data from Mppt in order to program the MPPT.

For execution Firstly i have set Mppt modbus address as 2. After that i have written ladder code for setting plc as master with required data baud rate etc as mentioned in manual. After that i have used special instruction ADPRW for reading command code as follow.  |ADPRW| H2 |H3 |K38 |K1 |D0 |which means |H2=Modbus address 2 |H3= Read Holding register| K 38 Modbus coil address(mppt has aPDU address mentined as 0×0026 which represent a battery voltage which i need to read in plc)| K8=device count|D0 =Destination device head. After that i write ladder in plc but after that also their was light blinking in sending receiving indicator. I have check all wiring connection but no output.

Edited 7 Feb 2017 by praty

[Clear.Mind 18]

Which one of channel do you use? Check communication error registers D8402/8422 depending of used channel.

[praty 0]

I am using channel1 and accordingly i have set Data in D8400 

[kaare_t 155]

If it's blinking in send/receive LEDs you are at least sending data. But it's impossible to say if the MPPT is communicating with the PLC. Since you are using 2-wire connection, the PLC will receive all information it's sending as 'echo' hence both lamps will light up. As @Clear.Mind is writing, what is the content of the error register?

[praty 0]

Thank you very much for reply!!!!

I am getting 211(Communication Timeout) in error register. After the first trail with MPPT, now i am trying to have Modbus communication between two PLC, but still did'nt got any success.

only thing i have got is MASTER PLC is showing sending led blinking and SLAVE PLC is showing receiving led blinking. I have used sample code given in Modbus manual for setting up the master and slave.

Might be i am wrong somewhere.

[kaare_t 155]

Are you still using 2-wire RS485? If so you should see both LED's blinking on the master, and only receive LED blinking on the slave when the master sends data. The other way around, when the slave responds with data both LED's should light up, but only the receive LED on the master.

Are you getting the same error message when communicating between PLC's, or a different error code?

[praty 0]

Thank you @kaare_t

I am using two wire system and have successfully connected PLC to Mppt.

Only task now i want to do is to write a single coil through on/ off.

For that i have read  modbus manual which has mentioned (H5) is standard modbus command, but i just want know how to give respective coil HFF00(ON) and H0000(OFF)  command through ADPRW instruction.

I tried one command as follow:

ADPRW H1 H5 H2 K1 X000

Which was showing X000 as off in monitor mode.

Really didnt understood what to do.

Required Help..

[kaare_t 155]

I'm not sure I understand.

You are trying to write the content of X000 to your Modbus slave device (Mppt)? What is happening in your system when you try to change the value of X000, and initiate a send request? Do you get an exception code in the PLC or the Mppt or is the communication working as expected?

If you have communication with the Mppt, why doesn't X000 transfer to the Mppt?

[praty 0]

Thank you @kaare_tThank you @kaare_t

Problem is solved i write the specific coil and controlled the MPPT