Do the CIM motors emit a magnetic field?

Has anyone heard that the CIM give off a manget field?

All of our motors have a magnetic field because every one has a magnet inside including the fans. Most are designed to concentrate the field within the motor but I wouldn’t lay a tape next to one and expect to get any data to play back.

Easy, way to check for magnetic field is is just use a CRT, slowly move the object towards the side of the monitor, as soon as it starts to distort, stop, if you get it too close, it can permanently damage the monitor.

With our monitors, a CIM will start messing with it from about 1 foot away, not that bad, but still pretty strong.

Why, you worried about it interfering with something?

May I suggest using a black-and-white TV, as they will not be permanently damaged if they come in contact with magnetic fields. But if you dont have one handy, then a CRT moniter and a quick hand should do the job :wink:

CRTs cannot be permanently damaged by simply putting a magnet near the the tube. It will distort and change purity but all of that should go away with a degausing. Whatever happed to taking a piece of steel (ferrous metal) and holding up to the motor to see if it sticks?

Yes, they have permanent magnets in them. If your looking at a digital compass you’ll need to keep it away from the motors and calibrate for hard iron fields.

can wood isolate/lower the magnetic field form motors?

I don’t Think so, not effectively anyway.

the only way i can imagine would wood help would be if you used it as a spacer :slight_smile:

I have no scientific backing, but my hunch is that you need some sort of dense material or maybe even dense ferrus material to contain a magnetic field…


To reduce a magnetic field you can do pretty much two things: move away from it or put a conductive material between you and it.


The magnetic field isn’t really that strong. It can pick up light things such as the master links for chain or staples. Then again, you shouldn’t put your electronics right next to it because it might mess it up.

out of all the motors the CIM is the motor with the most magnetic shielding and the FP is the one with the least. Cim’s are the most reliable motor in the kit. in the many years of their use in first robots i have never heard of one burning up breaking becoming disabled overheating or otherwise failing with the exception of wiring problems.

What about simply a compass?

To lower a magnetic field easiest would probably be a chunk of lead.

We dont have to worry about magnetic fields with our electronics because verything is solid state, and the data on the robot controller is not stored magneticly but written to memory.


Magnetic fields are interesting little beasties. You cannot block them with lead, wood, or copper shielding. Ferrous metals work to a certain degree but combinations of nickel, steel and other metals due tend to work in conjunction to shield the fields by bending them out of the way. A sandwich of high nickel steel, steel, and copper in alternating layers works best. There are a number of materials that are available for purchase but they are expensive and heavy. (Mumetal, guassshield and magalloy were some of the names I have used. I am not sure whether they were manufactured by companies now defunct or not.)
Fields to tend to reduce with distance but depending on the surrounding materials may actually be focused into a particular direction. Remember, magnetic fields, like elctricity, must flow from pole to pole so think of your classic bar magnet picture with the field curving from North to South poles.
Magnetic fields become particularly annoying to electronics when they are changing or moving. Remember that a wire will have current induced in it if it is in the presence of a moving or changing magnetic field. (Sometimes referred to as “cutting the (magnetic) lines”) But remember that creating a magnetic field with electric current is what drives our motors. The field generated in the armature works against/with the filed in the magnet of the motor.

could it mess up the control interface

I don’t know a lot about the physics of it, but I have never had a problem with motors disturbing any of the control electronics.

if you put a conducter near it, any movement will generate a current in the conductor and thus a field will form around it …

I would be surprised if it had any effect on the RC. IFI is pretty good at design and would have planned for this kind (and most) interference.

Which is true but the field strength overall will be less. Why? Because you don’t get energy for free. Some of the strength of the magnetic field goes into inducing the current in the conducter hence reducing the strength of the magnetic field overall.