wrap counter

Hi folks, this is my first time posting. I am a part time programmer and I am having issues with a wrap counter on a wire draw machine. Without getting into too many details, here is a description of what I want to do. My application has two proxys. If the following conditions are met, I want to increment a counter:
1st proxy comes on
Then second proxy comes on (first proxy is still on)
then first proxy shuts of (second proxy still on)
then second proxy shuts off
increment count
I also need to decrement the counter when the conditions are reversed.
Any help would be greatly appreciated. Just as a side note, my version of RSLOGIX 5000 only has ladder logic capabilities.

welcome to the forum.

you have done a great job with your description.

may i suggest either using an integer register and step through your logic or latch in a series of bits.

step 0 - bit 0 - enable logic
step 10 - bit 1 - prox 1 made
step 20 - bit 2 - prox 1,2 made
step 30 - bit 3 - prox 2 on, 1 off
increment counter or latch a bit
keep going in reverse order.

there are many ways to do this as you will learn.

hope this helps.
james

What you describe is the function of a common dual channel incremental encoder that operates by frequency phase discrimination. You don't need to write any code for this. All serios PLC makes have counter/position modules that handle this. Like Allen Bradley ControlLogix 1756-HSC (High Speed Counter).
Some PLCs like the Simatic S7-1200 has even integrated High Speed Counters where you can configure a pair of inputs to be High Speed dual channel incremental.

The phase relationship between two signals you describe is called 'quadrature'. Google it (and 'incremental encoder') for a lot of additional information.

Often the signals are presented too quickly for standard inputs and the scan of ladder logic to interpret so 'High Speed Counter' inputs (or individual cards) are used. But from your description the signals in this application are slow enough for evaluation.

You are asking for a 'times 1' or 'X1' count. X2 and X4 - with two and four counts per full cycle - are also possible.

First create a leading edge pulse (OSR) and lagging edge pulse (OSF) of the second prox.

Now create two additional rungs ...

If falling edge pulse AND the first prox is OFF then increment the count.

If leading edge pulse and the first prox is OFF then decrement the count.

To implement the X2 interpretation you would add two more comparison rungs looking at the edge pulses when the first prox is ON.

To implement the X4 interpretation you would create leading and falling edge pulses from the first prox then create 4 rungs comparing those edges to the ON or OFF state of the second prox.

Attached is the printout from a Micrologix program for reference. You should be able to implement an RSLogix 5000 version.

Thanks for your help guys, I will dig in and let you know how it goes...

just as you say you can use software for this (or selfmade or in oscat.de) for example, however if the speed is higher as 1 kHz you will miss pulses as the software can not keep up.
if this happens you will need a hardware counter. (in old wheelmouse there is this built in.

Got it working guys, thanks again for your help!