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#1 |
Member
![]() ![]() Join Date: Jul 2004
Posts: 44
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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. ![]() |
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#2 |
Lifetime Supporting Member + Moderator
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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 |
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#3 |
Member
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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.
Hope this helps Paul P.S I see Steve replied while I was busy typing one fingered ![]()
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There are 10 types of people in this world.. Those who understand binary and those who don't! |
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#4 |
Member
![]() ![]() Join Date: Jul 2004
Posts: 44
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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 |
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#5 |
Member
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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 |
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#6 |
Guest
Posts: n/a
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problem with conversion
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 |
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#7 |
Lifetime Supporting Member
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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
__________________
Regards Dave "When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity." Albert Einstein (1879-1955) |
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