Primitive humans may have discovered fire, but their descendants harnessed the more practical forces of electricity. The results of Hans Christian Orsted and Andre-Marie Ampere's early 19th century studies of electromagnetism can be seen today in modern hand-cranked electrical devices like radios, flashlights and even laptop computers. Increasingly popular technology among campers, travellers, the eco-conscious or those who want to be prepared in an emergency, building a homemade hand-crank generator is a fascinating way to learn about the relationship between electrical and magnetic fields.
- Skill level:
- Moderately Easy
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Things you need
- Plywood, about 10-inches long by 4-inches wide
- 2 wooden blocks, approximately 6-inches by 1-inch and 8-inches by half an inch
- Iron nail with head, 1/4-inch diameter, 6-inches long
- 75 feet of enamelled copper wire, 30 SWG or 0.3mm diameter
- 6V or 0.06A flashlight bulb or an LED
- Soldering iron
- Mountable D250H magnet
- Hand crank with threaded axle
Center the 6-inch block lengthwise from the edge of the plywood base. Ensure the block's narrow edge faces up. Fasten the block to the plywood base with nails or screws.
Center the 8-inch block against the 6-inch block and mark it half an inch above where it intersects with the shorter piece. Drill a hole large enough to accommodate the axle at the point marked in the 8-inch block.
Attach the drilled piece to the plywood base perpendicular to (in a T-shape) and about 3 inches from the 6-inch block.
Building the Base
Draw two circles with a 1-inch diameter on the cardboard and cut them out. Pierce a hole in the centre of each piece of cardboard with the nail.
Slide one of the circles onto the nail all the way up to its head. Wrap insulation tape around the nail, just underneath the cardboard, creating a 1-inch band on the nail.
Slide the second cardboard circle up the nail as far as the insulation tape. Use more tape to secure it in place so that the two circles form a spool.
Wind the wire around the area between the cardboard circles. Begin 12 inches in from the wire's end so that some wire is left free to attach to the bulb. Ensure the wire winds as neatly and tightly as possible. Continue winding until the wire is flush with the outer edge of the circles.
Wrap insulation tape around the spool of wire to secure it. Leave 12 inches of wire free to attach to the bulb. Cut off excess wire.
Place the nail assembly lengthwise along the 6-inch block of the base so that the spool aligns with the hole in the 8-inch block. Secure the assembly in place with staples or tape.
Slide the axle of the hand crank through the hole in its support block. Bolt or attach the magnet to the axle so that it sits as close as possible to the head of the nail without making physical contact.
Remove the insulation from the ends of the two loose wires. Solder the ends of each wire to the mounting for the bulb or LED.
Turn the handle to spin the magnet as quickly as possible. Rotating the magnet induces its field into the coiled wire, generating electricity and illuminating the bulb or LED.
Constructing the Coil
Tips and warnings
- The coil assembly alone can be used to detect magnetic fields. Try holding the nail head close to a speaker that's playing music to observe the light illuminating to the beat.
- To avoid electrocution, never use the coil assembly to detect magnetic fields from a building's wiring.
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