Encoder with Gray code


#1

Does anyone have experience using encoders with Gray code output? Can I use an IDC5Q module with an encoder that uses Gray code or reflected binary?


#2

I used to have good luck with the old (and very reliable) first generation (G1) IDC5Q for reading binary inputs. We then wrote our own decoder logic. One issue with the IDC5Q is that it wants over 10vdc on the input so it is not great with TTL levels. How fast is the grey code changing in your application?


#3

I don’t expect the shaft will be rotating very fast, probably in the range of 5 to 10 RPM. However, I have not seen the equipment yet and don’t know how many pulses per revolution the encoder is putting out.


#4

Ok, I guess I wanted to clarify that you are talking about an IDC-5Q and not a SNAP-IDC5Q which is a different animal. The IDC-5Q is what I have used to look at binary inputs. A SANP IDC5Q is a quadrature input module that I don’t think will work with gray code. What controller are you thinking about to read the inputs? Is it your own or one of the SNAP-PAC’s ? There are other 4 channel Snap modules that might also work if you are using a PAC controller.

Norm


#5

We would use a SNAP-PAC-R1. This encoder is just a small part of the project. We’ll have more than 100 digital inputs as well as a dozen or so analog inputs that we’re monitoring. There will likely be more than one rack of I/O so we expect to also use and EB-1 on another rack.


#6

Great, If you are on the PAC platform then there are several lower voltage (like SNAP IDCFAST) modules that might work even if the encoder uses TTL logic. The IDC-5Q you mentioned at the beginning will not work on a SNAP PAC rack.
Once you get the encoder you will know more about what module to use. Working out the decoder logic should be easy with Opto Script in PAC Control.
I would recommend a dedicated 4 channel module like the SNAP IDCFAST (depending on encoder outputs) for the encoder inputs and then look at the High Density modules with SNAP TEX break out boards for the less time critical inputs (SNAP IDC-32. etc…)


#7

Ok, I found the answer I was looking for. I need to use a SNAP-SCM-SSI module for encoders with Gray Code.


#8

I think that is right and I have used that module with ssi and it is really fast. Capable of 1 megabit inputs. Great for use on absolute encoders like magnerestrictive style linear units.