1794-VHSC to replace PLS

So I have a customer that wants to replace an outdated PLS (Programmable Limit Switch). The current system uses a resolver and 2 outputs in a stitching pattern started off a photoeye. Looks like a VHSC will work nicely. I've used them before, but never the integrated outputs and count tables, so want to make sure what I'm reading is correct. It appears the 4 outputs can be assigned up to 4 on/off window counts, and the count mode can be set to reset and start on a gate input, in this case the photoeye. If I need more than 4 count windows(not sure yet what the pattern is), I assume that I can use the two counters in the VHSC and just parallel the encoder, giving me 8 windows to work with? There are two sets of these 2 outputs (4 total), but the counts might run concurrently (two different parts of machine), so there should be no problem with TWO 1794-VHSC modules running in the same flex rack?

So in summary,

1) Parallel encoder can give me 8 windows

2) no issues running TWO 1794-VHSC modules in a single rack

We have replaced several of our Autotech Mini-PLS's that operate on a 360 degree cycle. We use one high speed counter module connected to the encoder and add an output module to the PLC chassis to replace the PLS's built in outputs. We convert the machines full cycle pulse count to 360 in the PLC program. Then use a limit test instruction to create the output windows. This way you could add more output windows if needed with additional output modules.

mjp123gp said:

We have replaced several of our Autotech Mini-PLS's that operate on a 360 degree cycle. We use one high speed counter module connected to the encoder and add an output module to the PLC chassis to replace the PLS's built in outputs. We convert the machines full cycle pulse count to 360 in the PLC program. Then use a limit test instruction to create the output windows. This way you could add more output windows if needed with additional output modules.

Click to expand...

Yep....that's what I'm replacing is the Autotech. Unfortunately, I'm having to reuse an existing CLX processor that's already running other equipment so my concern with going with discrete outputs in a 1794 chassis was RPI update to the rack and scan time. The stitching pattern is on/off in 60 to 100ms. That's why I was interested in the compare tables and outputs built into the 1794-VHSC as they operate outside of the RPI/scan time. And the local rack is too far away.