absolute encoders?

[ledieu]

ok - may be pushing my luck a bit but has anyone got the low down on absolute rather than incremental position encoders? I'm getting crazy data and too few options within the controller to adjust baud rates etc - do I need to zero it at start of moves?

 

[cutlunch]

I haven't used these but from my research different manufacturers do it differently. Are you able to post the make and model of the encoder also that info for the controller it is connected to?

Once I have this I maybe able to answer your question with some research.

I have also noted that depending on which encoder you use it may send the data in different formats ie grays, straight binary etc. Some of these encoders use a fixed method set at the factory others can be set on-site.

So if you look at the data does it make sense using some other encoding method such as Grays code. If it is Gray's code then as you move it small distances you should only see single bits change instead of multiple bits groups.

Something else I found in my research mentioned that in some cases the absolute position is set by mechanicaly positioning the encoder. In others a limit switch is used at the zero position so that when it is reached the encoder is then reset to absolute position.

I am sorry if this post has been no help and you already knew all I have said.

 

[ledieu]

Love your work cutlunch! You've just galvanised a whole bunch of unrelated info/research I have done into a coherant, logical format that I can understand (I dont speak German so the product docco is useless!). Its a TR electronic CEW58M. It does have an optional ability to perform site prograsmming but I haven't come across any drawings of how to make up the 422 cable - plus the program interface I downloaded is again in German so its a bit of a struggle. The controller is pure proprietry hard/software packege that stopped its development late last year - by the looks of it it stopped about half way through the absolute encoder interface section as the sections that deal with grays code, baud rate, bits setting etc all return that very comfroting command line message - "Parameter not currently supported". Always a joy reading that when you know no-one is aactually working on making it supported! I do get data but it suddenly jumps between blocks of positive and negative values for a linear motion device - side stage wagons. The controller only allows the 2 data and 2 clock lines as inputs. I've had a go at resetting with simulated limit switches at various voltages but dont seem to be getting any where.
I've got the wagons tuned up nicely with incremental encoders but really need to get to the bottom of the absolute encoders so i can cross reference signals in the next part of the job - stage lifts (two controllers, 2 VSD's, 4 encoders - one stage lift - who comes up with these stupid designs??)
Anyways - all really good info CL - thanks again

 

[cutlunch]

ledieu. The programming interface you use is that TRWinprog? If it is why aren't you using the english version? In case it is the same program we are talking about ( I downloaded it , Dial-up, took ages) I'll tell you how to switch to english. Just click on the menu heading called "Extra" then select "global" one line under the com port speed. It will currently show "GER" with a German flag next . Just change the option till it shows "ENG" which will show the Union Jack. If you click the option file automatic load box on the same page it will aways bring it up in English. This as well as the program changes the help menu.

If it is not TRWinprog but some other program they probably still have an english switch in the menu options.

Now to Rs422 issue from the help file I found that you need an adapter to convert the output from RS422 to RS232. Although you could build one buying a made up one would be quicker.
The interface should be fairly standard you can probably get it by trial and error.

I found these links which I think apply and are in English.
This one is shows different type of interfaces used on the CE-58. You just need to pick the right one.

http://www.trelectronic.com/index.p...aryEncoders/absolute/ce/ce58m/ce58m_index.htm

This one has the different interface manuals.

http://www.trelectronic.com/interfaces.php

The english homepage is

http://www.trelectronic.com
Hope this helps. Please let me know how you get on.

 

[ledieu]

There are some days you feel such a moron! Yes it is TRWinProg and, yes, by following you're instructions, turning it to english makes it a thing of beauty indeed!.
Next time you're passing through Malaysia (or wherever I am at the time) sing out and there will be several nicely chilled beverages with your name on them waiting on the bar!!!
I'll let you know how I get on. Cheers again.