Prevent a robotic cleaner from climbing on a block of iron with a magnet?

[CharlesT]

Hi,

very trivial question, sorry, but I did not find the answer on the net.

I have a robotic vacuum cleaner,
https://i02.appmifile.com/248_operator_sg/07/03/2023/b083a6129f828ac367c4600b0a78b85b.jpg?f=webp

and it's constantly bumping into and trying to climb on the massive iron one-pilar foot (ca. 30KG for the black iron base plus ca. 30 kg for the (surprisingly magnetic) stainless steel iron leg above) of a modern style dining table like this one:
https://immagini.designbest.com/immaginiprodotti/tavoli/big/3978-tavoli-70280-b-1.jpg

Now that cleaner like most of them has a magnetic field detector to prevent access to some zones and I could stick a magnetic strip like this:
https://www.aliexpress.com/item/1005002319655397.html?spm=a2g0o.productlist.main.1.32c02760OKW1JR&algo_pvid=a99932be-9305-49f8-8d7e-13e453009eef&aem_p4p_detail=202311170449327399213835089200000957758&algo_exp_id=a99932be-9305-49f8-8d7e-13e453009eef-0&pdp_npi=4@dis!USD!16.94!11.69!!!16.94!!@2103872a17002253728037584e2761!12000020067648197!sea!FR!712444402!&curPageLogUid=hfGIY1yuXvTB&search_p4p_id=202311170449327399213835089200000957758_1
all around that iron block, but it would not be very nice looking (tried it, plus the bands do not stick well).

So I'm wondering whether sticking on the table iron base, permanently, a strong neodymium magnet could magnetize the block sufficiently to make the robot detect it like it does detect these bands, and if so how strong that magnet should be...

Any help appreciated, thanks!

Charles

 

[Vanadium 50]

This seems awfully hard. Don't you have little IR transmitters you can place on the floor near areas you want excluded? Why invent your own solution when a trip the store will solve it in half an hour?

 

[CharlesT]

The IR is not adapted, it’s on the floor and I just want to exclude the base.

The magnetic band could be a solution as I said but I was wondering if magnetizing the bloc could not be a more original and elegant solution.

But to be frank I’m investigating this mostly for the fun of it and for the fun of learning something on magnetic fields: what is the threshold of the detectors mounted on the robot, the strength of the field of such a band and what is the relation between the magnetic field of a magnet and the one created within another material when the magnet is placed on it…

 

[Baluncore]

Experiment. Place a magnet on the floor and watch the robot's response.

The table base looks like it is made from cast iron. One might magnetise that during manufacture, but it would be difficult after the event. A magnetised base would be difficult to clean of magnetic grit before painting.

I would consider sticking small magnets to the periphery of the base. Experiment with all the same polarity, or alternating but spaced apart.

Maybe a coil wound around the circumference of the base, with DC current flow, would work to produce a vertical magnetic field outside the base.

The non-magnetic solution would be to raise the base, using 8 or more black rubber feet, by a few millimetres, sufficient to stop the robot climbing. Sticking magnets under the base might achieve the same outcome, and produce the keep-out warning field.

Alternatively, making a short cylindrical skirt, that sits outside the base of the table to form a wall, would stop the robot. You could make it from a strip of metal, plastic, or card, painted to match the base. It would need tabs under the table base edge, to hold it down.

 

[CharlesT]

Thanks, yes, I already had these elements in mind but for aesthetic and practical reasons they would not be adapted.
The preferred idea would really be to use a big magnet, put it permanently on the iron base, and have that one thus get magnetized sufficiently to have the robot cleaner detect its magnetic fiedl.
The question is: is this possible, or willthe magnetic field in all cases be to weak?
Also how does one calculate the magnetic field a magnet can indice in a given mass of iron?
Now even if I'd like to understand the theory before, I'm ready to experiment, but for that I'd like to have some idea of the size of the magnet needed, so not to invest blindly in something too small...

 

[Baluncore]

Now even if I'd like to understand the theory before, I'm ready to experiment, but for that I'd like to have some idea of the size of the magnet needed, so not to invest blindly in something too small...

Unless you know:
1. The sensitivity of the robot magnetic field detector, and
2. The strength and field pattern of a magnet,
you will be unable to solve this problem numerically.

Find a cheap magnet from anywhere.
Place it on the floor and watch the robot response.

 

[sophiecentaur]

a magnetic strip like this:

Not very expensive and worth a punt if you like experimenting. Trouble is that it could look pretty naff. Depending on your metal or wood working skills, you could make a hoop of the appropriate depth that could fit around the base actually look as though it's part of the design.
I can see problems with a permanent magnet sitting on the floor; It could accumulate loads of steel bits.
easy to experiment with thick card for a design first and then go for more permanent material.

or how about a disc to sit the base on to raise the step? Ebay has all sorts of wood and metal shapes available.

 

[CharlesT]

Thanks for the advice but this I already knew and is not an answer to my questions.
Never mind, just forget it.

 

[sophiecentaur]

Thanks for the advice but this I already knew and is not an answer to my questions.
Never mind, just forget it.

This is always a potential problem with 'agony aunt' topics like this one. Every contributor needs to go over the same ground, mentally as the OP. But sometimes someone else's journey can throw up something extra.

In fact, you have a double problem because you want to keep the aesthetics and none of the possibilities would ensure that. The only viable solution would be to check that a magnetic system would work then to permanently magnetise the base itself. If you are lucky the base may be in two parts - a shiny stainless cover and a massive iron base. The internals of the base could be magnetisable (or replaceable) on its own without spoiling the shine of the cover.