Radio and CIM motors

[jnelly]

If we place our radio only about a half inch from a CIM motor will we have issues with magnetic interference?

[cgmv123]

Don't put it that close if you can help it. Especially after the FMS issues last year, you are strongly advised to put it up high, not near a motor, and not behind any pieces of metal.

[DonRotolo]

Not magnetic interference, but metal has this way of not letting radio waves through it. The antennas need to be not near metal. Find somewhere else if you can, like on a piece of something not-metal and flat, up higher on the robot, and mount it with velcro.

[lior9999]

My team is mounting our wireless bridge inside of our electrical box at the bottom base of the robot (it's a rather tall machine). Do you think this could be an issue/cause us to have poor coms?

[Alan Anderson]

Originally Posted by lior9999

My team is mounting our wireless bridge inside of our electrical box at the bottom base of the robot (it's a rather tall machine). Do you think this could be an issue/cause us to have poor coms?

In a word: yes.

My advice is to keep it as high and exposed as you can without compromising the functionality of your 'bot and without risking having its wires snagged by other robots.

[DonRotolo]

Originally Posted by lior9999

My team is mounting our wireless bridge inside of our electrical box at the bottom base of the robot (it's a rather tall machine). Do you think this could be an issue/cause us to have poor coms?

Unless you have a non-metallic box and components (e.g., wires), yes.

Find some random space up high on the machine and velcro it there.
In past years we have lexan "sides" we use to display sponsor logos, we velcro it on the inside of one of those.

[jmiller18]

A simple sheet of aluminum, even as thin as aluminum foil, wrapped around the cim will lower the emi to negligible amount

[DonRotolo]

Originally Posted by jmiller18

A simple sheet of aluminum, even as thin as aluminum foil, wrapped around the cim will lower the emi to negligible amount

Electrical, yes, but this has no effect upon magnetic, since aluminum is not a conductor of magnetism.

[jmiller18]

Originally Posted by DonRotolo

Electrical, yes, but this has no effect upon magnetic, since aluminum is not a conductor of magnetism.

Ok then just go to your local osh or hardware store and pick up some dryer tubing, which is as close to steel foil you can get and rap it around ur cims

[Kevin Sevcik]

Originally Posted by jmiller18

Ok then just go to your local osh or hardware store and pick up some dryer tubing, which is as close to steel foil you can get and rap it around ur cims

Which will be entirely saturated by the large magnetic field of the CIM because it's so thin. Notice how thick the flux rings are on the BaneBots motors.

All of that is beside the point, however, because a CIM is still a big hunk of metal that is going to block radio from the field. Save yourself a headache and just put the radio somewhere away from metal and motors where it'll get good reception.

[Al Skierkiewicz]

While the CIMs are mostly steel the RFI from the brush assy. still will be emitted from the motor through the end bells and the wiring. Twisting the motor wires and making them short runs to the speed controllers helps a little.
The radio has two antennae, one on each side of the box. These are required for the 802.11 standard, they are not either/or (diversity). To insure maximum connectivity and throughput, your radio should be mounted away from surrounding metal of any kind and higher up in your robot. When metal is in close proximity to the sides of the radio, the antennae become detuned and output power is affected. When metal is close to the top, the same occurs. What you are trying to achieve is that the radio can 'see' the field antenna while you drive.

[jmiller18]

Originally Posted by DonRotolo

Electrical, yes, but this has no effect upon magnetic, since aluminum is not a conductor of magnetism.

also the routers use dipole antenna which use the electric field, not the magnetic, so that's all you need to block

[Al Skierkiewicz]

The radio actually uses PIFA antennae, vertically polarized to the plane of the bottom of the AP. The circuit board is the ground plane.
Antenna actually have both electric and magnetic fields, but they are 90 degrees apart. Most discussions center around the magnetic field so the electric field lives in obscurity.