Wiring differential encoder

[scrambled]

I am wiring my differential encoder and I have a question about which resistor to use. According to the manual--

For long cable lengths (beyond 3 meters), it is may be necessary to terminate
differential pairs with 120 Ohm resistors (connected from A+ to A-, B+ to B- etc). A 10
nF capacitor can be connected in series with termination resistor to reduce encoder current
consumption. Terminators can be soldered inside D-Sub connector housing or connect them
externally to EXT connector.

My local Radio Shack only has 100 Ohm and 150 Ohm resistors. Which of these should I use, or do I have to order a 120 Ohm resistor?

Is it ok to use ceramic disk capacitors ?


thanks



Steve

[Al_The_Man]

What make of encoder specifies this?
Usually the differential driver used is RS422/RS485 which is good for 4000ft.
If you really want to go ahead with it, 150 should work out OK. It is not that critical an application.
I have never seen this in all the differential types I have used.
Al.

[scrambled]

Al-

The encoder is an E5 1250 CPR from Us Digital. Here is the link.

http://usdigital.com/products/encode...5/#description

Do you think this is not needed? I am just trying to make sure I am not going to have noise problems.


Thanks


Steve

[Al_The_Man]

I have never used US digital, But I have installed many many differential encoders and not had a problem so far, I would try without the r/c first, you can always add it if you find it necessary.
Al.

[Xerxes]

Al is right. Try it without termination first, and 150 or 100 ohms will be fine if you decide to add line termination.

[scrambled]

Al-the-man---

Tero-

While I was flashing my servo drives, I discovered that two of my encoders have either failed, stopped working, or I let the smoke out.

The Specs for the USdigital encoders are here. It is a 14 page pdf file.
http://usdigital.com/assets/general/...atasheet_1.pdf


These two encoders are at the farthest point from the servo drives. I ordered 40 foot encoder cables, and I only trimmed about 2 feet from these two axis.

When I tried to monitor the encoder using GDtool, I only get a 0 for the encoder count.

So far I have tried moving the encoder cables and that did not help. I also plugged encoders mounted on other motors to the cables of the non working encoders, and I could read the non mounted encoders. So I am thinking the wiring is ok.


Tomorrow I am going to remove the encoder from the motor and remount it and see if that helps. I am also going to try to discover what part went bad by mixing two encoders and trying to get 1 reading.


Any ideas on what to do or not to do? So far I have not added any resistors or caps, so that is not the problem



Steve

[Karl_T]

I'll soon be doing the same thing on my 6x10 plasma table with USdigital encoders. let me know what you end up with.

Karl

[Xerxes]

Steve,

Sometimes encoder outputs bad signal or nothing if its little bit incorrectly aligned to optical disk. You may want to try adjusting readhead's position and test again. I would also add termination to 40 foot cable. 100-150 ohm resistors between A&B + and - outputs at drive end should be enough.

[keebler303]

I've found the US Digital encoders go together in a pretty foolproof manner. There isn't any real adjustment to the readhead, not on the ones I have used anyway (including E5).

I would try using a real short wire on the encoder to see if it is working with a short cable. Also check to make sure your connector is good and no pins are bent or damaged. I have had problems before with cheap connectors not making good contact if the pins are even the slightest bit bent.

Matt

[scrambled]

keebler303-

I checked all the connectors, and they look fine. I also made sure that the connector was fully seated in the encoders.

Tero-

I added the 100 ohm resistors to the y axis, and nothing changed.

I also removed the encoder cable to the y axis, and there was not a mark on it. I also used a meter and checked all the wires in the cable, and everything checked out.

I moved pieces and parts around, and I could not find anything bad.

Now one of the x axis encoders has stopped working. So now I have three not working
I am going to call US Digital tomorrow and see what they say.

Is it possible that the encoders and the VSD-E's are not compatible?

How can I test the encoders and not have them connected to the VSD-e???


Thanks for the help


Steve

[Al_The_Man]

You can check the outputs on a 'scope, alternatively if you use a meter from common to each output and turn as slow as possible you can see the transition 0-5v of each output, and the complements A, /A etc.
Al.

[Xerxes]

I have used several USdigital encoders (differential & single ended) with VSD-E without problems. There are rumors about weird problems with recent USdigital encoders (search for example Geckodrive forum).

If someone wants to donate problematic USdigital encoder, I would be glad to check it.

BTW, don't trust GDtool encoder counter too much as it gets updated as very low priority task. I have seen it freeze sometimes.