Gray encoder

pauly · May 9, 2006

I have an ssi encoder connected through a Stegman spa3 serial to parallel converter to my plc. I am converting the Gray inputs to an integer but the value instead of going to max and then to zero it is counting backwards from max to zero. I have had this problem before and I coudn't fix it then. Any ideas?

rdrast · May 9, 2006

The quickest, universal solution, is just subtract the actual count value (from the encoder) from the maximum count value.

If the encoder max count value is 1023:
1023 - Curr_Count = Direction_Inverted_Count

1023 - 0 = 1023
1023 - 1023 = 0
1023 - 1022 = 1 etc.

PLucas · May 9, 2006

Pauly

As you are using the SPA3 convertor you can very simply reverse the counting direction of the encoder by reversing the polarity of Pin10 on the 37 pin parallel connector, if you have this pin at 0V simply apply +VE to it and vice versa.

Paul

pauly · May 9, 2006

I should have explained a little better, the count goes from 0 - max and then instead of resetting to zero which I was expecting and counting to max again it counts down to zero from the maximum.
RDRast youre idea sounds good I'll give it a try.Thanks Plucas.

pauly · May 9, 2006

Gray encoder again

Hang on Rdrast if I subtract the actual count from the max count then the result will still be up and down surely??

bernie_carlton · May 9, 2006

Are you sure you have properly converted the Grey signal to an Integer? The description you gave is what an untranslated Grey signal, minus the MSB, kind of looks like.

SimonGoldsworthy · May 10, 2006

Post your Gray to integer conversion routine.

pauly · May 10, 2006

Gray conversion

This is the scheme I have followed but using 13 bits

SimonGoldsworthy · May 10, 2006

Your implementation for Gray code to binary is incorrect. I have edited your scheme below

panic mode · May 10, 2006

gray code conversion is very simple.
maybe this will help:
http://www.ab.com/sensors/support/reach/faq/archive/nov2000/1.html

pauly · May 11, 2006

Multi turn gray encoder??

Okay I get the conversion from Gray to binary, if I have a multi turn encoder how would that get converted? Same way or would you treat the "turns" bits differntly?
Thanks Pauly

Gray encoder

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