adccommunitymod (AutomationDirect) asked a question.
Created Date: March 16,2018
Created By: JeffreyH
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Click Ethernet Basic PLC C0-10DRE-D Click power supply C0-00AC for PLC power input devices are normally open PNP sourcing position sensors. If an input is specified as a pulse catch input (min pulse .010ms) what happens if the input pulse length should be longer than the system scan time? For example: the input pulse length is 50ms but the scan time is only 20ms. When the pulse occurs it will get latched in for 1 scan. But what happens when the next scan comes around and the input is still on? Is the input ignored? Does the click think its another pulse and latches it in for another scan? Does the input have to go off and then on again for it to be acknowledged at all (sort of like an edge detector)? The help file says that in normal operation (input pulse length shorter than scan time) "the circuit latches the Input event on the selected Input for one scan and turns OFF after the scan. " But does it if the input signal is still there? I ask this because I have a situation where the input pulse length may be very short and need to utilize the pulse catch feature but it is somewhat unpredictable and sometimes can be longer.
Created Date: March 16,2018
Created by: JeffreyH
Click Ethernet Basic PLC C0-10DRE-D
Click power supply C0-00AC for PLC power
input devices are normally open PNP sourcing position sensors.
If an input is specified as a pulse catch input (min pulse .010ms) what happens if the input pulse length should be longer than the system scan time? For example: the input pulse length is 50ms but the scan time is only 20ms. When the pulse occurs it will get latched in for 1 scan. But what happens when the next scan comes around and the input is still on? Is the input ignored? Does the click think its another pulse and latches it in for another scan? Does the input have to go off and then on again for it to be acknowledged at all (sort of like an edge detector)?
The help file says that in normal operation (input pulse length shorter than scan time) "the circuit latches the Input event on the selected Input for one scan and turns OFF after the scan. " But does it if the input signal is still there?
I ask this because I have a situation where the input pulse length may be very short and need to utilize the pulse catch feature but it is somewhat unpredictable and sometimes can be longer.
Created Date: March 17,2018
Created by: bcarlton
Lacking documentation or an good reply here just wire up an input source of your own and try it.
Created Date: March 17,2018
Created by: a agnone
I agree, just do it and see what happens. I had a co-worker who use to get so hung up on scan times. He almost would freeze up in panic before even writing code. i can only remember one time where scan time was an issue. turned out it was more of rung order than scan time. Don't be afraid to try it. I have a setup plc in my office I can do things like this before actually committing to it. Actually have a couple Allen Bradley plcs, a DL205 rack and a BRX rack, 6 " C-More and a C-More Micro on the wall I use to test things.