On 08/10/2017 11:09 AM, Les Newell wrote:
I have been chasing a noise problem on my lathe for some time now. I am using a 7i29 2kw drive and am getting a lot of noise on the encoders, even with filtering enabled at a pretty low frequency. I have tried just about everything I can think of. I made a simple near-field probe and did a bit of poking around. The 20kHz drive switching noise was strong pretty much everywhere. After trying various things I found a common mode choke on each motor output dropped the 20kHz noise down so it was pretty much undetectable apart from right next to the chokes. However I am still getting noise on the encoders. I have a spare encoder input on a 7i33 so I moved one of the motor encoders to that input. I am getting zero noise on that channel even though I extended the encoder cable to reach the 7i33 with 6 individual wires instead of a screened cable. Even with filtering disabled I see no noise. Unfortunately I don't have any more spare encoder inputs for the other axis.


Has anyone else had noise issues with 7i29 drives?

Les



My CHNC uses a 7I29 and a single end encoder on the X axis, works fine. All the wiring goes through the same flex guide. Make sure your motor leads are twisted to cut the noise.

Ed.


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