# Electro-Magnets

Hello evryone,

This is my first post on LMR for a long while, I used to be active under a diffrent username.

To get to the point, I'm intressted in biulding a robot that utilses electromagnets, I'm thinking of wall climbing. Is this possible/realistic? What kind of specs (Current, number of coils, length) would sutch a magnet have?

Nick

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Nicholas, I must ask, how you will get magnetic devices to stick to walls and ceiling? You seem knowledgeable enough about how to calculate the magnetic fields, so may I presume you must be in a room or buildnig that is made of (or covered with) ferrous metal...(?)

I put more to this post and now it has suddenly disappeared. Let me see if I can reconstruct what I typed before...

Ah, yes.  If you are using iron or nickel-iron or "ferrite" cores, I would think that it would actually be better. If you work the iron (bend it to shape, etc.) be sure and anneal it (soften it) again afterwards. Bending or hammering it tends to harden it and its magnetic properties decrease.  The only drawback I can think of would be if the residual magnetism made it stick to the wall or ceiling when it was not supposed to remain attached.

Are you making a wheeled platform or a walker, or what?  I do not know enough about what you have in mind with your design to know just what the effect would actually be. The mu constant relates to the type of material of which the core is made. For instance, I have ferrite cores here that have a full range.  from µ = 20 on up through µ = 10,000.

Thank you for your prompt response, I realize that my question was not specfic enough.

The bot will naturaly be kept small. 4 AA's, 4 HXT900 servos, little electronics, lightweight material... I'm guessing around 200g without magnets. I'd be useing 2. Assuming the magnets would weigh 50g each, I'd then have a combined weight of 300g, with a resulting gravitational force of 3N.

The two forces would have to be set equal, as the robot should "stick" to the cieling in our scenerio.

F(G)=F(B)

3N = (B^2*A)/u0 |A=Area of the E-mag; u0 = 4PI*10^-7

Assuming that my magnets both had diameter of 3cm (A=0.0028m^2) so that B is the only unknown variable:

B = u0*(n/L)*I |n=number of coils; L=length; I=current

The problem is that the above equation is for a coil magnet without a ferromagnet inside. Another problem is the current I. I know that 4AA bateries can provide a current of 1A for about an hour at 6v, but how would the situation be while driveing servos, supplying my Picaxe28x1 aswell as providing current to the magnets?

Hope my question was more percise, I apologise for any english mistakes, as I am not a native speaker.

will be difficult on its own, but, the smaller the bot the better chance you will have. Properly sizing electomagnets will take more research into the subject than I have ever done. You will need to know the mass of the bot including the batteries, and magnets. The question you are asking is too overly broad to get a solid reply, in my opinion.