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Old Apr 29th 2016, 04:49 AM   #1
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Electromagnet actuator increase power

Hello All,

I am trying to make a device that presses down on a foot pedal when activated. The main requirement is that it needs to be silent and powerful. I have tried other types of actuators and servos, but all are too noisy.

My next idea was to use an large electromagnet (salvaged microwave transformer turned electromagnet) to pull down an arm which presses the pedal. Photos of the prototype are attached.

I am applying 20V to the magnet and it is drawing 11A. When the arm is in a low position, the downward force is very high, but quickly drops as the distance increases. Ideally I want a lot of power at a distance of 10mm.
Currently it is able to press 4kg at about 5mm (electromagnet to metal plate), but only about 500g at 10mm.

How can I modify this to make it stronger?

Would any of the following help?

- increase the thickness of the plate being attracted to the electromagnet, it is currently 2mm steel sheet the size of the magnet

- change the shape of the steel plate

- change the electromagnet core: Do the transformer core laminations affect the strength? Would solid steel work better?

- move the copper windings up or down on the core (currently sitting at about half way).

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Old May 2nd 2016, 08:11 AM   #2
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Join Date: Apr 2008
Location: Bedford, England
Posts: 668
I don't know the consequences of your proposed actions, I don't know enough about electro-magnets etc.
I would suspect that moving the windings up might help
(if it is easy to do, then just try it)
If you could salvage a second transformer you could perhaps put two windings on the same core (but your current drain would then start to get a bit alarming)

Another idea which could be tried might be replacing the steel plate with a (correctly aligned) permanent magnet.
You have GOT to Laugh !
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actuator, electromagnet, increase, power

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