Micrologix 1500 HSC

I have a machine that I'm thinking about installing a PLC to control it's functions.

The machine uses a single output pulse generator attached to a shaft that the PLC would have to engage a clutch count the pulses till preset then remove the power to the clutch so I'm thinking High Speed Up Counter.

The other section of the machine would use a Quadrature encoder to determine machine angular position and turn on outputs based upon machine position.

Here is the thing I have a Micrologix 1500 out os use at the moment that is available. The base I have for it is the 24BWA base which from the documentation has 4 (20KHz) high speed inputs but the processor has two High Speed Counters. I was also reading somewhere that implied that inputs 0-3 are HSC0 and inputs 4-7 are HSC1; if this is correct would I then need a different base or would I be able to use the 4 inputs that I have for both counters?

Where do you see that there are only 4 high speed inputs? I show there being 8.

Even so, you can do it with 4. Setup your quaduture encoder on inputs 0 + 1 but don't set it up for hold in reset in function file. Then setup an EII on input 2 for your pulse

Check that manual and verify whether you have 4 or 8 high speed inputs first

Rockwell's Micrologix 1500 User Manual Page 1-2
1764-24BWA has 8 24VDC Inputs 4 Fast VDC inputs

But thank you for your info on using four high speed inputs.

Here is the thing I was reading The Micrologix 1500 instruction set and it says for mode 6 which is the Quadrature encoder, HSC0 is I1:0.0/0 - /3 and HSC1 is I1:0.0/4 - /7 so if these two documents are correct could you tell me further how do I share my 4 high speed IO for these two counters. I hope I'm not pulling my hairs out on this one.

You are right. I was looking at page A-4

Mode 6 would be correct and hook your encoder to inputs 0+1. Normally the hold and reset are assigned to inputs 2+3 but by not setting the mode to 7, they have no effect on the HSC.

Then assign an EII to input 2. Unlike the HSC, it triggers a routine. Make it a lean routing. For basic counting I usually have a simple add statement with an integer or long integer as source a, a 1 as source b, and the same integer or long integer as my destination.

Don't forget to lower your input filters in the I/O configuration for inputs 0-3

Ok that sounds workable I would give it a try but since I only need one HSC this way then maybe I can even use a ML1200 that I have. Thanks for the info prevented me from pulling out a hair.

Yes I have done it many times with the 1100, 1200, and 1400. I've never done it with the 1500 but it should work exactly the same

Just don't forget to lower those input filters!

Tim,
That is the second time in this thread that you mention the input filters, have you been bitten by that? I know I have.

YES! And the worst part is that you can't change them online.

I've got a machine right now that I need to lower them on. It worked find during testing a low speed, but it's having trouble at full speed. I can connect to it for a download through the VPN but don't want to take the chance of it crapping out being 4 hours away