Servo Encoder to G320x Signal Problem

[pupfield]

Using Keling DC Servos with US Digital E4P Encoders connected to Gecko G320x drivers, we are having problems with the encoder signal getting lost. It appears the signal is not happy traveling on wires that run near the servo motor power wires. We have tried several types of shielding, grounding, and other common things that should fix this. It seems to be a capacitance problem but can't get it to go away without seperating the wires. Hopefully we're missing something easy. Any help would be great.

[Bubba]

pupfield,
there is a known problem with these encoders and and the 320x. Do a search of the zone or go to the Gecko web site and look in the documentation section as I believe there is information there.

[Dennis Bohlke]

You need to convert the encoder signals to differential signals to stop the cross talk.

It's more a factor of inductance than capacitance.

Dennis
www.super-tech.com

[pupfield]

OK Ladies and Germs, here is what we have found.

1- Even though US Digital E4P encoders have no documentation that shows they act like HEDS encoders, the fix for our signal problem was the same. Add a 1 uF capacitor between +5 and G at or near the encoders and add 1K resistors from ENC+5 at the Gecko to pull up the A & B channels. We also used CAT5 UTP and paired each signal line with a ground. Now, no more signal problems.

2- When an encoder is described as 300 CPR and it is a quadrature encoder, it actually provides 1200 positions per revolution. This must be secret information because it was very difficult to find. A quick change to from 300 to 1200 encoder lines EMC and all is well.

3- Just because someone sells you a 5 thread per inch screw, if it comes from Hong Kong, it may actually be a 5mm pitch screw. Again, a change EMC from 5 turn per inch to 5.08 turns per inch and all is well.

Thank you.