controlling lots of channels

[ngoodman]

Not so much of a question but something I have found.

I have a system with around 300 channels from several plastic extrusion machines and other datacapture equipment. some OPC some modbus - controlling data capture from all of these was difficult and gave errors as channels sometimes read at busy times - when the OPC was polling for example. The system frequently fell over on start up as well. Altering timing in the channel view was difficult and time consuming

how I solved this was to set each channel and offset to zero and create a sequence that read each channel in turn one machine at a time with a gap to allow the opc to poll between each machine read

result

Reliable operation and start up and FASTER data capture times.

any comments?

[AzeoTech]

Its hard to say without knowing more detail about how things are setup. If, for example, all your devices were on the same 485 chain, but you were using DF Modbus and OPC at the same time to communicate on this chain, you definitely would see problems. For one thing, often with 485 multidrop devices, you have to add a small delay when switching from one device to another. This is because the transceiver on the first device hasn't released the line and so the second device doesn't get the signal.

Your solution did two things and is a good solution: first, by putting all your polling in a single sequence, you ensure that the polls don't try to occur on top of each other. Second, you were able to add the delays your hardware apparently requires.