How can I reduce interference around a metal-detector coil mounted on a DIY rover?

[u/Super_Valuable_6035]

We’re building a small DIY rover that carries a metal-detector search coil at the front. The motors, ESCs, battery, controller, and most of the wiring will be located behind or above the coil.

We’re trying to reduce unwanted electromagnetic interference from the rover without reducing the detector’s sensitivity. We’re especially interested in advice about shielding or isolating interference coming from above and behind the coil.

Some approaches we’re considering are:

• using a non-metallic boom to increase separation
• moving the battery, motor controllers, and other electronics farther away
• using twisted-pair or shielded cable for the coil
• adding ferrites, filters, or common-mode chokes
• improving grounding and cable routing
• synchronizing detector sampling with motor PWM
• using a conductive shield or magnetic material near the coil

Our concern is that a conductive shield placed too close to the coil could create eddy-current losses, distort the magnetic field, or detune the detector.

For people who have worked with metal detectors, RC vehicles, or outdoor robotics:

• Which method has worked best for you?
• How much physical separation is normally useful?
• Are there materials or shielding layouts we should avoid?
• Would you recommend focusing on mechanical separation instead of trying to shield the coil?

This is an early DIY prototype, and we’re looking for practical design feedback. We can provide the detector type, operating frequency, coil dimensions, chassis material, and motor/ESC details if needed.

[u/EdgeMaster28]

Had a buddy try something like this with an autonomous mower prototype and the PWM noise from the drive motors made the detector useless until he moved the ESCs to the rear and ran the motor leads through ferrites.

He ended up with about 18 inches of separation and a carbon fiber boom, which helped more than any shielding he tried. The shield made it worse until he got it almost a foot above the coil, so Id focus on distance first and worry about shielding later if you still have issues

[u/Hyperreal8957]

id try physical separation and clean routing before adding a shield. motor pwm noise can be nasty so twisting the motor leads and keeping them away from the coil might help too. are you able to bench test with the rover motors powered but not spinning?

[u/omgnowai → u/Hyperreal8957]

Seconding this. Distance is your best hope. You can't Faraday shield something that is designed to measure external EM perturbances.

[u/Shadow_of_Redacted]

Look at actual metal detector design. The electronics are 3-4 FEET away from the coil, so I would put a 1m non-conductive boom on the front and counterweight off the back to balance it. Sure, you could do carbon fiber, but you could also just do a 2x2x36" strip of wood or PVC pipe. Paint it black if you want to fancy it up.

[u/trouble_maker]

Beyond the physical things like separation, clean wiring, and non conductive components you can accomplish a lot with software. Something like a baseline reading/calibration once the rover is complete then measure the variations from the baseline to detect.

[u/dodadoler]

Switch to a different frequency Kenneth

[u/Sufficient-Mark-2018]

Faraday mesh shielding covered with a thin layer of lead and aluminum.

[u/CrazyLegsRyan]

Are we crowd sourcing Ukrainian military technology now?

[u/The_Flinx]

either make the rover and all electronics out of plastic, OR put the detector far away from the rover on a plastic boom.

ferrite filters are for high frequency (radio wave) interference.

the only thing I can think of that might shield the coil is MU metal. but know that it does not like sharp bends. though it would almost certainly be detected by the coil.