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Can you use standard choke inductors as electromagnets? Answered

I am making a project where I need very small electromagnets to attract and hold a small metal flap closed when the circuit is turned on. Flap is about 1cm from the magnet and returns to this position via a spring when the circuit is off. In theory is it possible to use inductors used in electronic circuits (for interference suppression etc.) as an electromagnet? Thanks.


I think not since choke-style inductors tend not to have very many turns but an electromagnet is all about having a lot of turns.

But - fear not - it is a piece of cake to wind your own electromagnet. I would recommend getting your enamelled copper wire from either an old transformer or an old CRT (the scan coils). Be careful when breaking-down an old monitor or TV set to scavenge for parts - the things to be wary of are the large capacitors which can still hold a charge for months after the last time the set was powered up and the tube itself which contains a vacuum and can explosively implode sending flying shards of glass everywhere.
The wire is insulated and so can be wound round and round the core with impunity. Make the connection to the wire by burning or sanding off the thin varnish layer.

Sounds like you need a fair amount of travel from the  valve. 1Cm is  a LONG way to just pull with an open electromagnet. You'd be better looking for "linear solenoids" like these.



not really. Wind your own, or better, as Steve suggested, scavenge one from a relay

 Hi, thanks for the advice everyone. I have just found a whole box of Omron GB6-2114P-US relays in my garage, score! However looking at the specs online it says that the coil rated at 12VDC has a current rating of 25mA and a resistance of 480 ohms. Enough current to pick up an iron filling maybe? 

I need to move the key on a saxophone and hold it closed. I know this is an extremely tough question to answer but any idea of what rough coil specs I would need to do such a thing? Maybe I should be looking at large relays from cars etc?

Sorry for the silly questions, my physics is some what lacking! Thanks.

Here's my take.

Since the relay has many parts than can be used to do the task, (it might require little more than popping the weather cap and attaching some sort of cam) it might be worth trying. The coil could be augmented rewound, or even overdriven (slightly) if it turns out to be close.

Since you have a box full, it's not like it'll be the end of the world if you trash one trying, and you can always save the pieces parts for a future project.

best wishes

Well in theory yes, they are coils of wire. In practice probably not, the DC resistance will be too low, and the number of turns to low to get enough MMF.  Just use a relay coil  - designed for the job.