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Step 2Wind the electromagnet
Although a solenoid by itself will produce a magnetic field when electric current is passed through it, a much stronger magnetic field will be produced if the solenoid is wrapped around a core of ferrous material, such iron or steel.
For this project, I cut some small shapes out of 7 mil steel shim material to use as the core. I marked off a tab that is the part of the metal that will actually be inside of the reader slot, and cut some grooves to keep the solenoid in place. When electric current is passes through the coil, the entire steel shim is magnetized.
For the coil itself, just use standard enamel-coated magnet wire. Wrap it until you run out of wire or space. The more turns you have, the stronger your electromagnet will be. Before you start wrapping the wire, cover the part of the steel around which the wire will be wrapped with tape or something to keep the coil from shorting out if a sharp metal edge bites through the magnet wire's thin enamel coating.
After you have wrapped the solenoid, cover it in electrical tape to hold it in place, and solder some wires on to the end of the magnet wire leads.
Make sure not to get tape on the metal face that will be pushed up against the stripe reader's sensing element.
**Thanks to Steve Moskovchenko for helping me to work out the positioning of the coil. **
For this project, I cut some small shapes out of 7 mil steel shim material to use as the core. I marked off a tab that is the part of the metal that will actually be inside of the reader slot, and cut some grooves to keep the solenoid in place. When electric current is passes through the coil, the entire steel shim is magnetized.
For the coil itself, just use standard enamel-coated magnet wire. Wrap it until you run out of wire or space. The more turns you have, the stronger your electromagnet will be. Before you start wrapping the wire, cover the part of the steel around which the wire will be wrapped with tape or something to keep the coil from shorting out if a sharp metal edge bites through the magnet wire's thin enamel coating.
After you have wrapped the solenoid, cover it in electrical tape to hold it in place, and solder some wires on to the end of the magnet wire leads.
Make sure not to get tape on the metal face that will be pushed up against the stripe reader's sensing element.
**Thanks to Steve Moskovchenko for helping me to work out the positioning of the coil. **
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Feb 25, 2009. 6:07 PMjockcoupzero
says:
I am troubleshooting here and I feel like the problem may be in the electromagnet. How powerful should it be when powered by a nine volt? enough to pick up a paperclip or a screw? How many feet of magnet wire do i need? I think I used 50ft starting with around a 3/4 inch wide sheet of steel sheet metal.
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