Electrical noise

#1

My motor is mounted on two load-cells so that I can measure the amount of force being produced. However, I am reading a lot of noise on my load cells, and it appears to be related to my motor or encoder. Below is a sample of the voltage measured after amplifying the signal from my loadcells. The blue line is the voltage measured by the Odrive at GPIO1, which is the output of the amplifier comparing the loadcells. The red line, only barely visible at the bottom of the graph is the motor current odrv0.axis1.motor.current_control.Iq_measured.

At the mid-way point in the graph i call odrv0.axis1.requested_state = AXIS_STATE_CLOSED_LOOP_CONTROL. This leads me to believe that my motor and/or encoder is the source of the noise.

The earth pin from my encoder shares earth with the amplifier & loadcells. The motor is also conductively connected to the load-cells. What is the best way to get rid of this noise?

image

#2

Hi Riewert, I think the load cell cable might be acting as a giant antenna picking up noise which is made worse by the amplifier. Maybe shorter shielded cables can help?

#3

I was able to remove the primary source of noise.

There is an electrical connection between this sensor and the motor through the aluminum CNC parts. I isolated the motor by using a plastic motor mount instead. Seems similar to what Oskar describes at Encoder error ERROR_ILLEGAL_HALL_STATE .

I did not need to add shielding or capacitors, though it is probably a good idea moving forward. First I need to replace all my cnc motor mounts with plastic parts though.

#4

Thanks for posting your solution I didn’t know metal frames can be a problem like that. btw cool looking project, hope to see more of this.