Analog Input as Multiple Digital Input

Mike Lamond · Jul 6, 2010

Plastic said:
At the 11th hour when functionality is added to the original design, we all scramble to make it work with what we have in hand.

One came to mind regarding this issue. Years ago we implemented one of the first generation Micrologix 1000 digital I/O only. The customer added a 2nd product model to the existing machine that needed different machining positions. We added a linear transducer O-10v to measure the axis, but were stuck as no analog expasion was available yet for the ML1000. We found a third party DIN rail module that was a analog-to-freq converter, and fed the frequency into the ML100 Digital Input 0 which was capable of high speed counting.

The axis moved slowly, so we merely interrogated how many counts happened in a given period, and found our anaolg actual position.

We once found a DIN-rail A/D converter that supplied the 12-bit output as a pulse train to a single digital input. The system needed more DI/DO that the Modicon Momentum combo base offered and we couldn't add a second I/O base for analog inputs. By setting the converter and the 984 ladder logic to the same fixed scan time, the PLC could sense the start pulse then reassemble the bits into the analog word.

Analog Input as Multiple Digital Input

Mike Lamond

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