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I am using a 5V borescope analog camera (Sony CCD, PAL/NTSC) for visualization purposes. This camera has a 20 meter 4 core wire, which transmits power and video signal to and from the camera. Along with this, I am using a servo motor (Siemens V90, takes 3 phase 415V AC) which moves pulls and pushes the 20 m wire (in turn moves the camera inside a pipe).

Problem: The image fed by the camera has lot of noise. I could make out that, the noise disappears when the servo motor and driver is switched off. Since the motor takes 415V and the camera is operating at 5 V DC, there is a signal interference.

Can you suggest any possible solutions to avoid the noise in the image?

Note: I have added the wiring drawing of the camera and the TV that displays the live video from the camera. The green circle is the 4 core wire I m using (one unused wire). Please let me know if more information is required about the servo drive/motor and camera.

enter image description here

The below image shows the noise appearing in the screen

enter image description here

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  • \$\begingroup\$ What's the DC voltage at the camera (after the 20 metres of cable) and how does this voltage vary under load conditions of the motor. You need to do a bench test and use an oscilloscope. Or just guess solutions, try them out and keep guessing solutions until you get success. \$\endgroup\$ – Andy aka Jun 28 at 10:40
  • \$\begingroup\$ @Andyaka: Thanks for the answer. I have not measured the voltage variation under various load condition. I will try it. Guess solutions ? Sorry not sure about this. \$\endgroup\$ – Soma Sundaram Jun 28 at 11:55
  • \$\begingroup\$ @Andyaka: Fixing any filters in the servo driver or motor side , will it help ? \$\endgroup\$ – Soma Sundaram Jun 28 at 11:56
  • \$\begingroup\$ Find the route cause of the problem and then make sensible adjustments. Guessing is still a valid technique though. When all your guesses (and fixes) amount some some tangible improvement try removing some of the fixes to throw away those that don't bring anything to the party. \$\endgroup\$ – Andy aka Jun 28 at 12:05
  • \$\begingroup\$ Is your cable shielded? If so, how is the shield grounded? \$\endgroup\$ – Cristobol Polychronopolis Jun 28 at 14:44
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Try a common-mode filter on your camera cable to reduce the aggressor noise. Test a clamp-on ferrite bead to start with.

Try to route the servomotor wiring in pairs that cancel each other.

Make sure that there is no ground loop from the motor sneaking back through another path: isolate its return.

Apply filter caps across the motor phases to reduce transients / ringing. (Make sure the caps are rated for this.)

Look for ways to control the spectrum of the motor drive signal (e.g., reduce slew rate, filter PWM hash better, etc.)

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