This project began much like many of my projects at Milwaukee Makerspace have: an off-the-cuff discussion; in this case, with Lance Lamont about a possible project for Maker Faire Milwaukee. After a few rounds of discussion, we came up with the idea of an electromagnetic crane. I decided I’d attempt to build one similar to this style, and that I’d start off with the magnet. I purchased several small electromagnets from Tom‘s favorite website, Banggood. Thus, the MicroMagnetArray was born:
And failed miserably. Running at 18v (50% more than its rated voltage!), it was only drawing ~200mA, and could only lift 2-4 of the 7/16ths nuts I’d borrowed for use as ballast.
So my inner maker came boiling to the surface and yelled at me, “why not wind my own!?”…
I present to you, failure #2: The small, drill-wound electromagnet:
This magnet was made from 28ga wire, and also ran at about 18V. It didn’t pull much more current than the previous one, and was also only able to lift ~3-4 of the 7/16ths nuts. I remembered Tom had a GIANT SPOOL of copper in his area, so I asked if he minded if I used a bunch of it. It turned out to be 17ga! After searching the ‘space for the right core (initially, a bolt, as shown in the previous photo), I found a nice piece of 1/2″ bar stock, and a piece of PVC tubing that the bar fit into perfectly. Once again, the drill came out, and I wound a much larger electromagnet:
This guy means business! It metered out at about 2.3 ohms. I fired it up with the bench-top power supply in the electronics lab, which immediately went into current-limit mode. At 6V DC, it was drawing 2.75A! I brought it over to the pile of nuts and it picked up about 15 of them! SUCCESS! According to Ohm’s law, if I run it at 12V, it’s going to draw close to 5A of power.. But the resulting field should be even stronger!
The original plan was to wind the copper around the PVC, but I would it too tightly and wasn’t able to remove the PVC afterwards. Oops! There was some debate as to whether a U-shaped core would be best, so that’s what I worked towards. After some testing, I found that the U-shaped core didn’t help at all, so I had Dan help me turn the u-shape into an eye. This will make it easy to suspend from a string.
Here’s a comparison of the three magnets to give you an idea for size..
Stay tuned for more photos of the electromagnet crane build!
(Also, for the Monty Python fans.. working on this project made me feel a little like the King of Swamp Castle must’ve felt..)