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| Did I get screwed on these electromagnets? |
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| TakeItUpANotch:
Hi! I need a bunch of electromagnets for a project I'm making. After some fiddling with a small set of electromagnets I realized I needed something beefier. My project will run on 12V DC and ideally I want as much electromagnetic force as I can get with those 12V at a reasonable cost. So I went on Aliexpress and ordered these: https://www.aliexpress.com/item/CL-P-25-20-Holding-Electric-Magnet-Lifting-5KG-50N-Solenoid-Sucker-Electromagnet-DC-6V-12V/32759668790.html They are rated to produce 50N at 12V and 0.34A requiring ~ 4W. After a fairly lengthy shipping process they finally arrived and I started testing the magnets out. Much to my surprise it turns out that these magnets were weaker than my previous smaller magnets at 12V. I was initially very confused and checked that everything was wired correctly on my project board etc. Then I just took one of the new magnets and plugged it straight across a 12V power supply and measured, and they only draw about 0.136A at 12V. The resistance of the electromagnets are around 88 Ohms and this makes sense if you consider I = U/R = 12/88 ~ 0.136A. Have I been had here? Looking at standard formulas for electromagnetic coils the force produced is proportional to the square of the current drawn, which means that I'm getting only about (0.1364/0.34)^2 = 0.16 = 16% of the electromagnetic force that was promised. Am I missing something here? I appreciate any input. |
| TakeItUpANotch:
On a side note - if I end up getting stuck with these magnets (no return or refund), would it be reasonable to have a step-up converter to 24V and run the magnets off of that instead in order to get a beefier current/force? I'm going to pulse the magnets and they will only operate at about 2-3 seconds max at a time, do you think that might produce any thermal issues? |
| T3sl4co1l:
Wouldn't surprise me if they are actually 24V. :-// They're a ball of wire, if they get too hot at 24V you'll know. Can probably run 48V if it's for a few seconds.... Tim |
| Nusa:
With Aliexpress, confirming delivery is basically the same as saying "I'm happy with this purchase." You have to look at how they use it, not just the words themselves. Once you confirm, aliexpress releases the funds and are pretty much out of the picture so far as helping you goes. If you haven't confirmed, you can start a conversation about having received the wrong product or a product that doesn't meet specs. If you don't like the results of that conversation, you can open a dispute. I never confirm delivery until I've verified I got what I ordered, or at least what I expected to get. |
| TakeItUpANotch:
--- Quote from: T3sl4co1l on July 21, 2018, 03:17:53 pm ---Wouldn't surprise me if they are actually 24V. :-// They're a ball of wire, if they get too hot at 24V you'll know. Can probably run 48V if it's for a few seconds.... Tim --- End quote --- Fair enough, I might give it a shot. --- Quote from: Nusa on July 21, 2018, 04:14:19 pm ---With Aliexpress, confirming delivery is basically the same as saying "I'm happy with this purchase." You have to look at how they use it, not just the words themselves. Once you confirm, aliexpress releases the funds and are pretty much out of the picture so far as helping you goes. If you haven't confirmed, you can start a conversation about having received the wrong product or a product that doesn't meet specs. If you don't like the results of that conversation, you can open a dispute. I never confirm delivery until I've verified I got what I ordered, or at least what I expected to get. --- End quote --- Solid tip, I'll keep that in mind. I don't think I ever confirmed the delivery. Either way I've opened up a dispute now. |
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