Making an electromagnet...

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I have promised to make an electro magnet/solenoid for my grandson. Even
though I used to make them when I was a kid, I am blowed if I can now
get one to work effectively. Currently I have egg on my face! I took
some wire from a transformer which is about 0.5mm dia and I am using a
ferrite core.
I have no idea what the wire gauge should be, nor the number of turns or
the required current to give a magnet that will lift more than a couple
of paper clips!
Can anyone help me?

DD

Re: Making an electromagnet...



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You're better off with a closed magnetic path if you can find something
magnetic with the correct shape, ie. U shaped with flag parallel ends, the
coil wound round the middle, and picking up something that closes the gap
like an iron plate or bar. A wide cross section and not-too-long arrangement
will work better.

Since you're not interested in the finer points of magnetic behaviour, you
may find ordinary iron or steel works better than ferrite.

For something around the size of your fist, maybe a couple of hundred turns
of #20 or #22 enamelled wire, a 12 volt DC supply and a bit of resistance to
keep the current from getting too high and burning out your coil. #20 is
good for a couple of amps IIRC. Google will give you resistance / metre for
various wire sizes.




Re: Making an electromagnet...



"DD"
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 **  Err -  what shape is the core.

    Not ring shaped I hope.


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**  Forget ferrite - it has a low magnetic filed strength.

Try using a  1/2 inch dia,  6 inch long,  mild steel bolt with about 250
turns on it.

 Even a 1.5 volt D cell should do the trick with that.





......   Phil







Re: Making an electromagnet...


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Mild steel will work much better than ferrite but magnetically soft iron
or silicon steel would work better: if you could salvage the E cores
from a plugpack transformer and run power to the low voltage secondary
you should have something fairly usable to begin with.


Re: Making an electromagnet...



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Try about a hundred turns of wire around a roofing nail & power it
with a 'D' size battery. That's how the demo was usually done when I
was a schoolkid.

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