[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.

[H.O]

I know most people experience no problems with USDIgital but personally I've had nothing but trouble. This app uses another drive but I thought it might be worth mentioning anyway.

I was constantly losing position when using the USDigital encoder (E7P). Measuring the output of the encoder indicated it was fine (voltage level, symetry, phase shift etc) but it simply refused to work in the application.

I switched motors, tried three different E7P's, I switched drives, I shielded, grounded, filtered, terminated, bypassed, tried powering the encoder with a battery, I tried long cables, short cable, single ended, differential - you name it I tried it.

I also tried three other encoders (Hengstler, AMT and Renco) and they all worked fine just fine even with 15 meters of cable rapped around a running VFD - no problems at all.

Just my experience....
/Henrik.

[scrambled]

Tero-

I am using GDtool to see the encoder count. Is there a better option?

I have a 4 ch o-scope that I will connect to the encoder. I will try to take a picture of the screen and i will post it.



Steve

[chamsodick thai]

i don't know:withstupi

[scrambled]

H.O-


I may need to change encoders, what type do you like?


Update-

ok went to the shop tonight and started to figure stuff out. I connected my o-scope to the EXT connector on the VSD-E drive. This was the easist for me, and this way I could see what the VSD-E reads from the encoder. I did not have any resistors or cap. installed.

Now before anyone jumps on me for having a setting wrong on the o-scope, I am not an expert, but I can get basic information out of it

When I checked the two x axis I would read the a,a-,b,b-. The i,i- would never change. I am not sure if this is normal.

It appears that the y and z encoders are dead. The a,b and the a-,b- would read either positive 5 vdc or 0 volts, but they would never switch positions when I would spin the motor by hand.

I am going to call US Digital on Monday? Any ideas what caused them to die?

Something else I found. There is alot of noise on the encoder voltage. When the HV power to the drives was connected to the drives the noise was there. if I e-stopped the system, and removed the HV, the noise went away.

I am attaching some pictures. On some of the pictures, I changed the voltage settings so that the pictures were larger and clearer

One two of the pictures that show noise, one is from the VSD-E and the other is from the power supply

Let me know what you think


Steve

[Al_The_Man]

The cheapest ones I have had the most success with are Renco.
The I or index pulse is hard to catch as it is only once/rev.
As regards the noise on the 5v, a 5uf across the supply at the encoder end may clear it up.
Is your 5v source from the PC? if so I would bond the power supply common externally to the ground plate, rather than rely on the M.B. screws to ground.
Al.

[scrambled]

Al-

The VSD-e uses 12 v and then converts the 12 to 5 volts.

I will look at the renco encoders.

Do you think the noise might have killed the encoders?


Steve

[H.O]

H.O-
I may need to change encoders, what type do you like?

Well, anything except USDigital...
I'm using Renco R35i and they are working perfect. Only doenside is they're using a not so common connector but that's not really a problem if you get the cables from Renco. They are more expensive than USDigital but they work in real applications.

[Karl_T]

The cheapest ones I have had the most success with are Renco.

I need to order encoders. Allways with USdigital before. Think I'll try Renco.

http://www.renco.com/index.php?WCMSGroup_4_3=8

I need differential with index, I assume this is the gating option? I assume i should order one of the 300 kit numbers, they all look the same, any differences?

Where do you go for encoder connectors and cable, look like renco doesn't supply.

karl