Distributing line tracking encoder pulses

Hello everyone! First post, long time lurker.

We have a conveyor/paint system that has an odd way of distributing the line tracking encoder pulses(at least to me anyway ).

The 'A' pulse from an encoder is fed into an input of a micrologix 1100 1763-L16BBB. Every 8 pulses it outputs a pulse which I'm assuming is per inch of travel. This output pulse is fed to the input of 3 separate micrologix 1400's running paint reciprocators in other panels spread out.

The outputs from the 1100 used are 0/0 and 0/1 which I believe are solid state outs. Yes, two 1400's are fed from output 0/0 and one from 0/1 .

I get a nice clean raw signal from the encoder on my scope, but the output from the 1100 pulses are varying frequency and time period. We believe this is causing an issue with painting in the wrong areas of our product.

The output of the 1100 travels through shielded blue hose to the 1400's panels.

Is this an acceptable way of distributing the line tracking pulses?

varying frequencies? assuming the encoder is tracking the conveyors per inch of travel, depending on the encoder type if absolute or incremental (read manual), will have s resolution, through which you can use to get your frequency, usually if this is a tracking application you would probably have a shift register.

I would suggest to see if your double counting or better known as "debounce". Sometimes you can have chatter that can cause a double pulse when their should have been just one. You can do this simple test with a counter on the encoders input.

You might be running into scan time issues as well. I'd give a shot with an external dedicated divider, and just feed that output to all three PLC's.

http://www.erma-electronic.com/english/signal_converters/selection_signal_converters/ft9003_en.html

for example

Do you have access to the 1100's program?
If possible, I would look at what it is doing before I tried to change things.

The encoder is an incremental, 300 PPR Accu-coder. Not sure of the conveyor rate of travel, but it is fairly slow. The pulses on the output of the 1100 jump around alot, hard to get a trigger on them. Seems they should be more consistent. Also, their pulse width varies. This is in contrast to the input (encoder) signal which displays on the scope as a pulse train as expected.

cncsparky said:

The encoder is an incremental, 300 PPR Accu-coder. Not sure of the conveyor rate of travel, but it is fairly slow. The pulses on the output of the 1100 jump around alot, hard to get a trigger on them. Seems they should be more consistent. Also, their pulse width varies. This is in contrast to the input (encoder) signal which displays on the scope as a pulse train as expected.

Click to expand...

Are you certain that the output of the 1100 is intended to be a rate divider of the encoder? You've seen this in ladder logic?

You would need to know the ratio of conveyor pulley revolutions to encoder revolutions and the conveyor pulley diameter to determine the pulse per inch