G306 HMI to Unidrive SP comms

[ROAMER_AUS]

Not sure where to go with this, sorry. Not that it helps you, but I've daisy-chained 30 Modbus devices to a similar Redlion device without even terminating resistors.

You could try the isolator I suggested before. I've never needed it for Redlion equipment, but have needed it for other Modbus Masters.

Thats OK. Thanx for trying to help. As I mentioned I think unidrive comms port
has a hardware problem. I'l put some osciloscope signals screenshots when I get better. Still sick.

Thanx again.

 

[ROAMER_AUS]

Hi All,

Just to put closure on the topic as it may be useful to someone sometime. As suspected, Unidrive SP had some sort of hardware problem on comms port. Signal was noisy and was just below treshold of being reckognised as logical 1 (don't remember exact voltages from oscilloscope). I didn't have much hope nor time to do investigate / repair surface mount technology and PCB in question would cost me more than new drive since drive was smallest in the range. So the way I solved it (or rather patched it up), I added one RS232 to RS485 converter to communication bus with it's own supply and biasing resistors with nothing on 232 side. This helped smooth out the signal from Unidrive SP and raised signal level above treshold. Comms are working for about 10 days now without problem.

Thank you all for your help again!!!

 

[osmanmom]

the mystery still there.