Need advice on A1SJ71AT21B

[ckkhin]

I have this 2nd hand machine which uses 4 of this A1SJ71AT21B to communicate between 3 A1SCPU (1 as master station and 2 as local station) and 1 A1SCPU(S1).

I have no previous experience with this network module. The only reference I got is IBNA-66478 which I got from Mitsubishi website. To my surprise, the connection differs from what the machine originally had.

The original connection of the machine for SDA/RDA and SDB/RDB are the same as manual. But the twisted pair cable shield are connected to SG(L) instead of FG. Also, there is no 110ohm,1/2W resistor connected in between SDA/RDA and SDB/RDB for the first and last station.

Anyone with experience on this?

[tgoulding]

Hi ckkhin,

Worked on Mitsubishi PLC's with MELSECNET network many moons ago. Ideally the shield should be connected to the FG terminal for proper screening and end resistors should also be in place to prevent reflection and errors.
I have however seen this type of network work without end resistors. What is the problem with your application? I assume that the PLCs are communicating with each other? If more help needed come back and I'll see if I can disturb the codwebs more.

[ckkhin]

It was communicating until I changed the connection to follow the manual.I used 2 resistors of 1W each to get 110ohm as I'm short of resources and it caused the last station datalink unit hardware faulty.

So, I replaced the datalink unit and revert to original wiring. To my dismay, the datalink unit of the last station hardware faulty again.

Do you know what is the different between LG and FG for A1S61P power supply unit? The last station wiring for A1S61P is different from other station. The Earth wire is connected to FG instead of LG.

To reduce down other possibility, I already clean up all the A1S38B base units and the modules of the machine. Now I am waiting for the datalink unit and already placed order for 110ohm, 1/2w resistor.

Hopefully everything will is fine by following the manual exactly.

[ckkhin]

For your information, this control is used for Crabtree 1290.

[tgoulding]

It was communicating until I changed the connection to follow the manual.I used 2 resistors of 1W each to get 110ohm as I'm short of resources and it caused the last station datalink unit hardware faulty.

So, I replaced the datalink unit and revert to original wiring. To my dismay, the datalink unit of the last station hardware faulty again.

Is there any chance you mixed up the cables when reconnecting or that the resistors are not on both ends but somewhere in the middle. Or is there a possibilty that two nodes have the same address.
Can you specify what LED's are on, cable distance approx. between nodes and what speed network is set to.

Do you know what is the different between LG and FG for A1S61P power supply unit? The last station wiring for A1S61P is different from other station. The Earth wire is connected to FG instead of LG.

As per the manual LG is grounding for the power supply filter and FG is the grounding terminal connected to the shield pattern of the printed circuit board. In any of the applications I've worked on the mains earth has been connected to the LG terminal. Maybe somebody else here knows better.

Generally the MELSECNET is pretty straight forward, once the cabling, resistors, addressing and speed are correct then it should work. Maybe replacing the troublesome network card or switching with a healthy one may help in narrowing down the problem.

[ckkhin]

There isn't any error LED. But when I diagnose with MELSECNET, the BWY from master station Unreceived. The 2 faulty datalink unit also gave the same outcome. Distance from master to last station less than 100m. Baud is set to 3. The 4 stations are set to 00, 01, 02 and 03. Double confirm the ohm before connecting it in (somewhere between 106-107 ohm).

Now I am connecting exactly as what shown in the manual and changed the FG to LG for power supply grounding. Also replaced with a new datalink unit. Everything is fine and hopefully it won't have any problem.

Having trouble modifying 1 of the PLCs program. I'm not sure why. Is there any write protect mode dip switch for A1SCPU? It is using A1SMCA-8KE memory cassette. Do you know the website where I can find user manual for A1SCPU PLC?

Thanks for helping.