10 Bit Encoder Decoder/ GE90-30

[Control Freak]

Anyone have any simple ways to decode the 10 bit grey scale code from an absolute encoder? My customer spec'd this unit and now I get to figure it out. I know some PLC's have decoder functions, however I know very little about them. In this case I'll be using a GE series 90-30 with an IC693APU305 (some processor module), also spec'd by the customer.
Silly me, doing it the easy way with Prog Limit Switches all this time. Way too easy, I suppose.

[Steve Bailey]

Think of the APU305 as a programmable limit switch module for the 90-30. It can accept absolute encoder input, so there should be no need to decode anything. It's a special version of the High Speed Counter module.

The manual for the module is publication number GFK-1028, available from the GE Fanuc website.

http://www.geindustrial.com/cwc/gefa...IO/s9030-m.htm

[PLucas]

Control Freak

I use grey code absolute encoders on our cranes, these input into a GE series six PLC. This is the code I use for decoding our gray scale inputs, I am sure this will translate straight into a 90-30, or be very close.

 GREYCODE                              BINARY

  BIT 10                               BIT 10

---| |----------------------------------(   )





 GREYCODE     GREYCODE                 BINARY

  BIT 9        BIT 10                  BIT 9

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 9        BIT 10    |

---|/|-----------| |-----+



 GREYCODE     GREYCODE                 BINARY

  BIT 8        BIT 9                    BIT 8

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 8        BIT 9     |

---|/|-----------| |-----+



 GREYCODE     GREYCODE                 BINARY

  BIT 7        BIT 8                    BIT 7

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 7        BIT 8     |

---|/|-----------| |-----+



 GREYCODE     GREYCODE                 BINARY

  BIT 6        BIT 7                    BIT 6

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 6        BIT 7     |

---|/|-----------| |-----+



 GREYCODE     GREYCODE                 BINARY

  BIT 5        BIT 6                    BIT 5

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 5        BIT 6     |

---|/|-----------| |-----+



 GREYCODE     GREYCODE                 BINARY

  BIT 4        BIT 5                    BIT 4

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 4        BIT 5     |

---|/|-----------| |-----+





 GREYCODE     GREYCODE                 BINARY

  BIT 3        BIT 4                    BIT 3

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 3        BIT 4     |

---|/|-----------| |-----+





 GREYCODE     GREYCODE                 BINARY

  BIT 2        BIT 3                    BIT 2

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 2        BIT 3     |

---|/|-----------| |-----+



 GREYCODE     GREYCODE                 BINARY

  BIT 1        BIT 2                    BIT 1

---| |-----------|/|-----+--------------(   )

                         |

 GREYCODE     GREYCODE   |

  BIT 1        BIT 2     |

---|/|-----------| |-----+

Hope this helps

Paul

P.S I see Steve replied while I was busy typing one fingered

[Control Freak]

Thanks guys.
The parts aren't here yet, but I want to stay ahead of the game rather than playin ketchup. Hopefully the APU unit is as easy to use as it appears. I've never worked with the GE platform at all, so this should prove to be an interesting experience. banghead
John
"there are 10 people..." <--- clever

[Doug_Adam]

I had this problem a little while ago as well.
Using a truth table I worked out that this converter was a series of XOR gates.
I then found an old text book with the same information in it.
If you notice, PLucas has also given the same answer.

Doug

I see a small problem with the gray to binary conversion diagram that was drawn out by PLucas. Please correct me if I'm wrong.

The first XOR has to be the next bit of the gray code XOR'd with the first decoded Binary Bit and so on. Like this:


Gray MSB Bin MSB
---||-----------------------()---


Bin MSB Gray Bit6 Bin Bit6
---|/|------||--------------()---
|
Bin MSB Gray Bit6 |
|
---||-------|/|---------

Bin Bit6 Gray Bit5 Bin Bit5
---|/|------||--------------()---
|
Bin Bit6 Gray Bit5 |
|
---||-------|/|---------


And so on.

Hope this helps

[504bloke]

JohnW has a logix 500 attachment for an slc 505 prog here

http://www.plctalk.net/qanda/showthr...ight=gray+code

It may be helpful