Ryandevlin17

Micrologix 1400 recording off time of a DI

5 posts in this topic

Hi,

 

I'm pretty new to allen Bradley and wanted to know if there was a function that could help me out. I have a rotation sensor which feeds back to the PLC via a digital input, once every half second or second once machine is up to speed - I want to record the off time of this DI (how long it is off between pulses, essentially how long it takes for drum to rotate once). Is there some way to record this time and use this value for compare logic? any help would be greatly appreciated.

 

PLC: Micrologix 1400 series B

RSLogix 500 version 11.00.00 (CPR 9)

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You could use the bit (not bit), a timer, and some logic to store the time elapsed value from the timer

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Is there a way of getting elapsed time from timer in Allen Bradley - I am used to Tia portal and using the ET function of timer block, is there anything similar I can use here?

 

EDIT: I have written a short bit of logic here will this work or will the unlatch zero the ACC value before its written to F register?

 

 

rot_sensor.png

Edited by Ryandevlin17

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You could also use the RTO instruction. Run the timer while the input is off. When the input turns on, grab the timer accumulator to do your math and then RES the timer.

 

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Thanks very much both of you for your help I will try using the RTO as opposed to TON

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