I'm a mechanical engineer enthusiastic about learning electrical engineering and I speak french so I thank you in advance for your comprehension and your help.

I would like to be able to activate an electromagnet to pull a pop-up switch throught a thin stainless steel wall (1 mm or 1/32 inch). I'm using an arduino but I guess an external power source will be necessary.

The magnet need to pull a spring to drain a liquid from a tank.

I know thant it would be easier to use a solenoid valve but I can't change the piping.

I was thinking of a u-shaped metal rod wire copper wiring and a relay but I guess that would need a lot of power. Which way would you recommend to achieve this goal?

Once again thank you for helping a mechanical engineer to convert to the electric engineering!


First of all, wow thank you for all theses excellents answers!

Is there any way for me to give you a positive feedback?

Secondly, the tank is non-magnetic but that is an excellent comment and I will need to be careful.

I think a lot of small magnets would do a pretty good job. This is so simple that I did not think about it.

I will try that and will update my post once I succeed!

  • \$\begingroup\$ Your horseshoe magnet design is going to require a lot of power to work. Better to use an electromagnet directed axially. \$\endgroup\$ – Hearth Feb 4 at 3:46
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    \$\begingroup\$ In a U-shaped magnet most of the magnetic field (outside of the magnet itself) is between the ends of the U. You would want to wind a wire around the pipe to make a magnetic field that goes in the direction of the pipe, then loops back around. \$\endgroup\$ – immibis Feb 4 at 3:51
  • \$\begingroup\$ I assume you want to pull evenly on the metal disk. Instead of a horseshoe magnet, two or three or four straight magnets, all pulling in the same direction would be better. Or, if you can install it, a hollow solenoid that goes around the pipe. \$\endgroup\$ – TimWescott Feb 4 at 5:49
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    \$\begingroup\$ What sort of stainless? If it's a non- or not-very magnetic alloy like 303 then this is a pretty good idea. If it's a 400 series alloy that's got significant magnetism, the tank wall will "short out" the magnetic circuit, and you'll rely on whatever can bleed through. That'll take a much stronger magnet. \$\endgroup\$ – TimWescott Feb 4 at 5:50
  • \$\begingroup\$ A big rare-earth magnet (or magnets) on a motorized lever may take less power. \$\endgroup\$ – TimWescott Feb 4 at 5:51

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