1734-IK Counting issue power off

[ronny_resistor]

Hello everyone a quick question that should have been asked already.


I have a 1734-IK counting card that can hold an entire length within itself. Great no resetting of count (rollover issues)so this is ideal 900 pulse = X # of inches / 12 gives me number of feet. Perfect.


So the internal count = 34789667 and we loose power on the machine. guess what.. my count is now zero (0) how do I retain the previous length count so that on a power up (FS, first scan) my program starts where I left off.


There are several hardware methods (none are really practical) including a Battery backup or UPS. I would prefer to do this in programming. Also I can be off by a couple of 1000 pulses.


We are using an L16 controllogix processor


Thank you in advance

 

[gclshortt]

http://www.plctalk.net/qanda/showthread.php?t=95865

The above thread may help you out.
"Every program scan, just read the value of the counter, subtract the value from the last scan, and add the result into a memory register."

Regards,

 

[Ken Roach]

The basic application is why absolute encoders exist; so you can retain the count value of an encoder through a power cycle.

Manually doing that function with the main PLC, over a network, is more complicated and requires more effort, as Lee found out in that thread five years ago.

If your machine is frequently powered down or can lose power abruptly, you should look into an absolute encoder.

If not (especially if the machine is stationary when powered down and the axis does not move) then you can use the stored value -> Configuration method investigated in that linked thread.

 

[sprek]

I couldn't find a straight answer to this question so i did some research and this is the code i got to work for me