Battery Powered Electromagnet capable of holding 500 lbs!

This is a lifting electromagnet from www.sciencefirst.com which is capable of holding 500lbs with just 2 D cell batteries! It costs about $55, but is quite a nice unit! It is their model number 20-035. They also have a slightly smaller electromagnet, model number 20-030, for about $47, which will hold 200lbs with just 1 D cell battery! The smaller unit is also available from ScientificsOnline (Edmund) as P/N 60-435.It is made of two parts - the yoke which also contains the coil, and the plate. The secret to the large holding force is that the plate and yoke are carefully machined so that there is no gap between them when they are placed together. It came with some excellent instructions on experiments you can do with it. However, I modified the larger unit a bit in order to make it easy to use on my wooden stand. Here's what I did.First, I removed the battery holders that came with it. Then I soldered longer wires to it, along with two banana plugs and a 9v battery clip in order to connect an ammeter in series with either a 2 cell AA battery holder or a 4 cell AA battery holder from Radio Shack. I also put a cable clamp on it so there wouldn't be any strain on the wires from the coil assembly. Then I put a longer eye bolt into the plate, and secured it with a flat and lock washer.Audio Speakers

Speakers are made by placing a one layer coil of wire, wound onto a tube, into a magnetic field. The end of the tube is attached to the center of the paper cone of the speaker. When current is passed through the coil, a force is created on the coil, causing it and the tube to move within the magnetic field. When the current reverses direction, the coil and tube move in the opposite direction. This uses the Left Hand Rule.The photos above show a speaker and a magnet used for a speaker coil and its tube. The field is between the center post and the outer portion of the circular slit.The speaker shown in the lower three photos will be dissected so you can see what the insides are like.

First, cut the wires going to the terminal strip. Then take a mat knife and carefully cut the cone around the edge. Let the knife follow the metal frame.

Next, you will need to hold the cone away as you carefully cut the inner paper disk, usually brown colored. You can then lift the cone and voice-coil assembly out of the magnet and frame. You can see how the magnet is made with a circular slit in it, where the center is a South pole, and the outside ring is a North pole (at least in this speaker). As current flows through the coil, it interacts with the magnet. The faster the current changes direction (the higher the frequency of the signal), the faster the cone moves in and out creating a higher frequency sound. The larger the magnitude of current, the farther the cone travels in and out of the magnet, the louder the sound. Connecting a battery to the speaker will cause the cone to pull in or push out a bit and stay there as long as the battery is kept connected. Reversing the battery connection will change the direction the cone moves (if it went out first, changing the battery around makes it go in the second time). Use a 1.5V battery for this test. This same effect is also demonstrated with the Fleming Left Hand Rule demo.

These are close-ups of the magnet, and the cone and voice-coil assembly. The voice-coil is the electromagnet, or solenoid. It is made with a very fine (small diameter) wire, with only two layers. It is then soldered to the flexible wires which you see on the left which attach to the terminal block. These wires are very flexible since the whole speaker cone goes in and out of the magnet in order to create the sounds.

The speaker in the upper left is one like the 5" speaker cut open above. The larger speaker is a 15" woofer from Radio Shack. Place some small wooden or glass beads into the middle of the speaker cone, and attach a signal generator to the speaker terminals. As you vary the frequency and volume, the beads start to dance on the cone. Fun to watch!Electric Lifting Magnet Holding Electromagnet Solenoid Lift 2.5Kg 12V DC 3W

Description

Description: Electric lifting magnet Powerful and compact Smooth and flat surface Low consumption and reliable Widely applied in automations: assembly line, sorting machine, mechanical arm, experimental facility, etc Input Voltage: 12V DC(If you need other voltage please contact us before order or leave message on paypal, otherwise we will only ship 12V DC, thank you very much) Current: 0.25A Power Consumption: 3W Holding Force: 25N / 5.6lbs Diameter: Approx. 0.8 inch / 20 mm Center Diameter: Approx. 0.3 inch / 8 mm Height: Approx. 0.6 inch / 15 mm Lead Length: Approx.9.1inch / 23 cm Thread Size: M3 Model: ZYE1-P20/15 Material: Metal Color: ChromePackage Includes: 1 x Holding Electromagnet