# DIY electromagnet

#### dragon

Oct 31, 2022
116
So what kind of power supply and conductor do you need to make a really strong electromagnet?

#### Minder

Apr 24, 2015
3,334
What is the end purpose? Lift magnet ? The commercial ones range from 24vdc to 200vdc. Magnetic power is decided by end use.

#### dragon

Oct 31, 2022
116
Does it work at 1volt (post transformer volts) as long as u use a step down transformer? (pre transformer volts is still high.)

<edit>
sorry for short post, i am a little dizzy right now, i need a few days off smoking.
</edit>

The end purpose is a really strong solenoid, to pull on a robot arm with a guitar string as a pully cable.

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#### kellys_eye

Jun 25, 2010
5,282
Far simpler to purchase one of the correct rating (voltage, pulling power etc)

#### dragon

Oct 31, 2022
116
Definitely, I'm more doing theory than practice, I just to like to know a few more things about magnetivity, like can it be done at low voltage output from a stepdown transformer? (Cause the amps are very very high.)

#### John Canon

Jun 1, 2022
81
I just did a search for "book electromagnet projects"
and discovered a wealth of information to help narrow your quest
to become "All Things Electromagnetic."

#### dragon

Oct 31, 2022
116
Thankyou for the suggestion. I'm more of an electric field type of guy than a magnetic field, but since u cant have one without the other, you definitely have to learn it even if u'r not even using an inductor. (cause the wire is one! hehe)

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#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
12,880
The magnetic field in an electromagnet is created by the current, not the voltage.
In theory a very small voltage (e.g. the 1 V as requested in post #3) can create a strong magnetic field if (and only if) the resistance of the solenoid is small enough to allow a high current (e.g. 100 A @ 10 mΩ).
In practice the resistance of the solenoid (usually made from copper wire) is way higher than that. Therefore you need a higher voltage to drive the same current.
Or much thicker wire, which is impractical due to size, weight and cost.
Or use superconducting wire. Then your "only" problem is cooling .

#### Sunnysky

Jul 15, 2016
529
I think you will be very disappointed with a linear magnetic actuator for force, power and size to pull a robot arm with a wire.

You would do far better with a small gear motor and large spool to take up the wire with loop to push-pull and spring tensioner pulley for the wire.

#### dragon

Oct 31, 2022
116
Yes Sunnysky u r correct, it is weak, but imagine the reaction time of the robot, it would be below 10 milliseconds!

#### kellys_eye

Jun 25, 2010
5,282
it would be below 10 milliseconds!
Doubtful - probably 30mS if you're lucky. Then again, what's the point? If you can even get a 'millisecond' movement time you have to consider the loads involved. Getting a sub 1-second movement of a 10g weight is a lot easier than getting the same sub 1-second movement for 1kg - what weight is the 'arm' and what weight might it be carrying? Not gonna happen.....

#### dragon

Oct 31, 2022
116
Doubtful - probably 30mS if you're lucky. Then again, what's the point? If you can even get a 'millisecond' movement time you have to consider the loads involved. Getting a sub 1-second movement of a 10g weight is a lot easier than getting the same sub 1-second movement for 1kg - what weight is the 'arm' and what weight might it be carrying? Not gonna happen.....

It would be a matter of volts/amps, to get it stronger. Another prob is the battery usage/wastage, but maybe u don't always have it on full blast its only when it needs it.

<edit> but ur right f=ma. the more mass the less accelleration. (a=f/m) </edit>

#### kellys_eye

Jun 25, 2010
5,282
It would be a matter of volts/amps, to get it stronger
To a point. You have to consider saturation as well as the coils own inductance (its ability to resist the rate of change of current flowing through it).

Read up on inductors and magnetism and you'll find the technical details on the how's and why's of solenoid construction plus their ability to 'pull' (or push) etc.

#### Sunnysky

Jul 15, 2016
529
work out the Ek , kinetic energy = effic.* electrical energy , magnetic force to reach max speed, displacement then repeat to stop.

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