Re: [CAD_CAM_EDM_DRO] Re: Major encoder trouble, need advice.

As I recall, you have tried at least two encoders with, more or less, the
same results. Is it possible the problem isn't with the encoder at all, but
the control or driver?

If I read your reply correctly the cable is quite short, only 300 mm or
around 12 inches, that shouldn't be long enough for any real cable problems in
any case. I have run cables for 5 volt encoders for well over 50 feet with no
problems most of the time.

In some cases where I was not getting the voltage swing from zero to a good
positive voltage, I used either pull up resistors, 10K or even in some cases
as small as 1K. One of the best solutions I use when I have a problem with
the voltage is to fabricate a small interface board with simple NPN bipolar
transistors, such as a 2n2222 or 2n2222a to clean up the signal and drive the
square waves to the full positive voltage. It isn't a fancy integrated
circuit, just some transistors and resistors, but it works. This way, if you have
any noise on the cable this simple circuit will pretty much clean that up as
long as it isn't enough to falsely trigger the transistors.

In a perfect situation, you would have some spare encoders and
driver/controllers to swap out and make a definite diagnosis as to which is the problem.

If the signals you are getting at the driver/control end are clean, and I
think you indicated they were, then it should work and that would also tend to
eliminate any problem with the cables.

Randy Abernathy
Industrial woodworking machinery installation, design, repair and servicing
Over 24 year experience with factory training
Fax: 770-974-5295
Phone: 770-974-5295


In a message dated 9/26/2008 10:45:45 A.M. Eastern Daylight Time,
henrik-olsson@... writes:

Hi Randy,

Your $0.02 is as appreciated as anything else!

All measurements have been made at the connector where the signals enters
the drive electronics. I haven't looked at them at the encoder end, partly
because it's hard to access them there.... ;-/

The cable I'm using for the USDigital E7P encoder is 300mm long and is sold
BY USDigital to be used with THIS encoder so I'll be damned if it isn't the
correct one... I initially used this cable which was then extended with my
ordinary cable but when that didn't work I thought I'd use the USDigital
supplied cable until I get THAT working - that's almost four weeks ago :-(

The shield of the encoder cable is now connected at the star-point GND but
was previously connected to GND in the encoder connector on the drive - and
there only. It made no difference moving it.

Thanks!
/Henrik.

-----Original message-----
Henrik:

I see that you have checked the signals with your oscilloscope but you
didn't mention at which points you made the tests. Is there any difference
in what the signals look like at the encoder and what they look like at the
other end where they are input to your controller?

Did U.S. Digital specify twisted pair to be used with their encoders? I
have always used normal shielded cable, not twisted pair. Many of the
encoder manufacturers I have used actually specify twisted pair NOT be used,
these are much higher priced units that U.S. Digital and that may be the
reason.

Another thing to keep in mind is to not attach both ends of the shield,
only connect one end of it to ground or the negative side of the power
line, I didn't see where you said how you had attached the shield.

Now, none of this may help but I thought I would put in my "two cents"
worth.

Randy Abernathy
Industrial woodworking machinery installation, design, repair and servicing
Over 24 year experience with factory training
Fax: 770-974-5295
Phone: 770-974-5295



------------------------------------

Addresses:
FAQ: http://www.ktmarketing.com/faq.html
FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com

Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...,
timg@...
Moderator: pentam@... indigo_red@... davemucha@...
[Moderators]
URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO

OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
http://www.metalworking.com/news_servers.html

http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.

NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
bill
List Mom
List Owner

Yahoo! Groups Links









**************Looking for simple solutions to your real-life financial
challenges? Check out WalletPop for the latest news and information, tips and
calculators. (http://www.walletpop.com/?NCID=emlcntuswall00000001)


[Non-text portions of this message have been removed]