5V Electromagnet (3Kg Holding Force) (DFR0794)

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This is a placeholder topic for “5V Electromagnet (3Kg Holding Force)” comments.



This is a DC sucker type electromagnet with 3kg holding force and 1W power. It should be operated at 5V. The magnetic poles of the electromagnet can be changed by … read more

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How heavy is the unit?

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Hi Kamilan,

I’ve just weighed a unit from stock, and with the minimal packaging included, it is about 27g.

Let us know if there’s any more info you need!

-James

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Thanks mate!

That is heavy for such a small item. Cheers!

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Hi Kamilan,

It’s actually 27g, typo!

All the best with your project!
-James

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LOL thats better!

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Hi,

I got this electromagnet a few days ago and played around with it to use in my project.
I was going to use the electromagnet to pull a metal screw that is attached to a 3D printed arm weighing around 70 grams.

I supplied 5V to the electromagnet and I can see it’s drawing 210 mA, which would be the full current draw based on the specifications. But its pulling power is very poor. Unless I put the screw closer (about 1 mm gap) to the electromagent, it doesn’t even pull the screw at all.

I thought that 3Kg Holding Force would have decent pulling power. Did I assume wrong?
I like the 5V power and the physical dimension of the item. Is there another electromagnet, which has higher pulling power in the similar physical dimension?

Thanks,
Chan

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It needs to be actually touching a flat surface to achieve the 3kG holding power.
How far does the screw have to move? If only a short distance a solenoid would be your best bet. This is designed to “pull” something whereas an electromagnet is designed to “hold” something.
Cheers Bob

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The screw needs to move 3mm. The screw weighs about 1 gram on its own and the electromagnet barely pulls (just) the screw in around 3 mm distance.

I tried to stick the electromagnet to a flat surface of a toolbox weighing about 2.8 Kg. The voltage was 5V and it drew about 250 mA to its full power.
However, it had no way to hold the toolbox afloat. It couldn’t even lift a tiny bit of the toolbox from the ground.

I also tried with an adjustable spanner which weighs about 800 grams. The electromagnet could pull one side of the spanner up but it couldn’t pull the whole spanner up.

The wires of the electromagnet in the product picture is blue, but mine is both red. I’m not sure if this matters though.

I’m thinking that the item is defective or not as advertised.
What are my options here?

Thanks,
Chan

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No it doesn’t matter. Like a solenoid it is not polarity sensitive. I am not familiar with this device so don’t know what its limitations are
Cheers Bob

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The product description says the actual holding power is 5-10 times less than what it says. And, that’s about what I have got.
I didn’t realise that the holding power and pulling power are different as Bob said.
I have assumed wrong about its pulling capability.

I still need a more powerful (more pulling power hopefully) electromagnet with similar physical dimension in either 5V or 12V. I try to avoid a solenoid due to the nature of my project.
Can you suggest one please?

Thanks,
Chan

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Finding one with more power and the same dimensions and the same power supply is a bit tricky.
There is a number which has a direct bearing on the “strength” of an electromagnet. It is called “Ampere Turns”. The product of the current (Amperes) and the number of turns. To increase the strength you need to increase one or both of these terms.

  1. Keeping the same supply voltage, same number of turns:
    Increase A = lower resistance = larger diameter wire = physically larger coil = larger unit.

  2. Keeping the same supply voltage, same current (A).
    Increase number of turns = same overall resistance = larger diameter wire = physically larger coil = larger unit.

  3. Keeping the same number of turns, same size wire:
    Increase A = increase supply voltage = same size unit.

Condition 3) is dependant on the current carrying capacity of the wire used without overheating. If this figure is quoted as “free air” conditions it has to be de rated to allow for mutual heating as the wire is wound in a coil. Wire and general insulation too is an important factor as higher voltages could cause breakdown.

So you can see the only way to increase magnet “strength” and keep the same unit size would be to increase the current by increasing the supply voltage. This has limitations of its own as outlined above.

Hope this helps a bit
Cheers Bob

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Not necessarily. If you can make the screw more magnetic then that would increase the pulling power. A steel plate attached to the head of the screw might do the trick, or even a magnet…

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That might work. There are rare earth magnets around about 5 or 6mm Dia. One of these glued to the screw head may work. If the electromagnet tries to reject instead of attracting reverse the electromagnet connections.
Cheers Bob

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Hi Chan

Just had another light bulb inspiration.
What is that screw made of. Has to be ferrous metal. Brass would be a no no and stainless steel not much better.
Cheers Bob

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Thanks Bob and Jeff for your inputs.

I’m not sure about which type of metal the screw is but it sticks very firmly to a small rare earth magnet. Very strong pulling as well, which gave me the inspiration to use an electromagnet for my project.

I tried with higher voltages (6V and 7V). It drew around 350 mA of current at 7V. I could feel that it pulls and sticks little stronger. However, the electromagnet got warmer than usual after about 15 seconds of use. Maybe using higher voltage is not recommended as it’s designed for 5V usage?

FYI, the screw can’t be magnetic as the 3D printed arm with the screw must swing back to its original position naturally when the electromagnet is demagnetised. I guess if the screw is magnetised there is chance that it will still be stuck with the electromagnet regardless.

Thanks,
Chan

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That pretty much discounts that method. It looks as if the wire is operating pretty much toward its limit.

That is a risk. It would be possible that the screw would retain some magnetism over an extended period and would need degaussing ever now and again. You may have a better chance with an AC magnet which should not leave any residual on the screw.

You could experiment. You would need a transformer of about 240V to say 6V step down and a Variac to raise the voltage gradually while monitoring current and temperature. The Variac would be your stumbling block here.

A bit of info on AC electromagnets here How to Make an AC Current Electromagnet | Sciencing
Cheers Bob

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Thanks for the information, Bob. I will explore that path as well.

In the meantime, I will try to find a way to make use of this item somewhere else :slight_smile:

Thanks,
Chan

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That magnet may work on AC. That is why I described that experiment with a transformer and Variac if you can get access to something like this.
Cheers Bob

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