Will large parallel magnets interfere with arduino?

I am trying to use an arduino and some optical sensors to measure velocity of a large falling object which is decelerated at the bottom of its fall by synchronous linear permanent magnet modules which use magnetic field to slow down the metal fins protruding from the dropping object. If I were to have the arduino near these magnets, would the magnetic field mess with the current, the timing, or do other undesirable things?

Has anyone had any experience with magnetic interference on this scale?

Thank you for your help!

You’ll probably be ok with static fields. Just ensure that the arduino cannot move relative to the magnets: attach the PCB firmly, and secure all wires thoroughly with many cable-ties so that they cannot move. Use tightly-twisted pairs to carry any analogue signals. I would not expect the resonator providing the CPU clock to be affected, even by strong fields, but you should check (with the “blink” sketch and a stopwatch).

If the magnets are very large, place any semiconductors as far away as possible. How far that needs to be depends on the size of the magnets and whether you’re using an iron yoke. Small magnets are much less likely to cause any problems - even if the field at the pole face is very strong, it will drop very quickly with distance. If the field near the Arduino is too weak to move a paperclip I wouldn’t worry.

it will drop very quickly with distance.

It is an inverse cube law actually.
In general magnets are not a hazard to electronic devices.

Grumpy_Mike:

it will drop very quickly with distance.

It is an inverse cube law actually.

Only if you're far away from the magnet relative to its size - where the field is probably too weak to be relevant anyway. For eddy-current braking the magnets may be very large, but they may also have a yoke which will concentrate the field lines and reduce the external field.

Great, thank you.
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Only if you're far away from the magnet relative to its size - where the field is probably too weak to be relevant anyway. For eddy-current braking the magnets may be very large, but they may also have a yoke which will concentrate the field lines and reduce the external field.
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these are eddy-current braking magnets and are very large. I am not sure about the yoke, these are the magnets: http://velocitymagnetics.com/dynaBrake.asp

But you're thinking even though they're large, it should not affect the arduino? How about an LCD screen: if the wires are held securely in place and neither the magnets nor the LCD screen are moving relative to the magnets, could I avoid interference?

OK, that clarifies things. There doesn't appear to be a yoke as such, and although the steel mounting will reduce the stray field somewhat I would expect the field within a few cm of the magnets is still pretty powerful. It all depends how near is "near". If it's a metre then you've got nothing to worry about.

I expect your biggest worry will be shock from the falling object causing wires to vibrate. Check the signals from your sensors carefully and under real conditions.

PS. The phrase "synchronous linear" in the company brochure is pure bull. It don't mean nuffin'. It just sounds better than "some magnets on a stick" :slight_smile:

haha, just magnets on a stick.

Thank you for your help!

Assuming these are neodymium magnets you might get about 1 tesla or so, which will induce 1 V/m for each 1 m/s in velocity in conductors (probably not a worry, basically). However various components on the Arduino board are magnetic like the USB socket and will clamp to the magnets given a chance...