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seabiscuit101

Square Wave Problem With Micrologix

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Hello all, this is my first post. I am using an AB Micrologix 1400 (1766-L32BXB Ser C FW 21). I was trying to generate a pulse train using the PTO instruction. I have modified PTOX funct. file. The ladder is just a simple XIO followed by PTO, (The Quick Start ladder from 1766-RM001). When I looked at the output waveform on my oscilloscope, I noticed that it wasn't a square wave. I decided to run it at several different frequencies to see how the wave form would change. At 10Hz i got a square wave. As I increased the frequency the falling edge became sloped and almost horizontal. Is this how the output should behave? The data sheet indicates a max frequency of 100kHz, but at frequencies over 150 Hz. The wave form looks like the output of SMPS. 

Edited by seabiscuit101

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Did you connect the dc common to the comm2 terminal? Also do you any load on your output or are you just looking at it not connected?

 

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