I have a control system using iso RS-485 using ADM2682E - But someone wants to use it over a BNC link (standard video cable). We have managed it, but are there any recommendations we should be aware of for this? Is it just plain bad behaviour?
This is not an ideal application, but if you describe how you have this connected (a diagram would be helpful), we can try to give some recommendations? Are you using one or two BNC cables? How are the ADM2682E/87E bus inputs/outputs connected? What length is the cable?
Thankyou for the response! I’m well aware that it is not ideal! Some customers don’t seem to care, so long as it works.
I have the ADM2682E connected as full-duplex – the BNC cable (just the one COAX) is approx 100m, and is connected: CENTRE CORE to PL6-1 & PL7-1 (A,Y) : SCREEN TO PL6-2, PL7-2 (B, Z) according to the schematic below.
It worked over a short distance, but in order to get 100m, we had to link the BNC screen to 0V of the PCB (green trace in schematic)! The customer suggested this method as he had another piece of kit which worked the same way! Odd, but...
can you confirm that in principle that the ADM2682E should work over BNC (i.e. two wires) for a half-duplex two-wire connection since the isolated GND2 (pins 9 and 16) is just a receiver current drain to an earth ground (as in fast-ethernet), rather than a signal return? Or is it needed to establish a common mode reference?
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