This is an AC electric generator which lights up a tiny incandescent light bulb. The generator is made from a hollow-ended cardboard box with a nail through the center. The box has many turns of varnished thin copper wire wound around, with four large magnets clamped around the nail. When the nail and magnets are spun fast by hand, the little light bulb lights up dimly. I wrote this article because I found lots of projects for making a simple electric motor, but nobody gave the secret for making a generator. Well, here it is: use strong magnets, lots of fine wire, and a special light bulb which only needs 1/2 volt. Also, don't bother making a "commutator," just hook the wires directly to the bulb. It's much simpler that way, but the generator will produce AC (alternating current).
Before you start, here are some notes: DON'T USE DIFFERENT PARTS. You must use a special light bulb. Normal flashlight bulbs will not work. Also, you must use the large, strong magnets shown in the parts list. Smaller magnets won't work. Use thin wire with varnish insulation. The wire must be #30 gauge or smaller. Also, you can improve the generator if you buy lots of extra kits of wire and wind it on the cardboard, since the bulb will light up even when the generator spins slowly. Three kits of Radio Shack wire is expensive, it's cheaper to mail-order just one or two Open-frame box solenoids, but you'll, need vise-grips pliers to pry apart the steel frame and remove the spool of wire.
4 - 1x2x5cm ceramic magnet: teachersource.com M-700 or Radio Shk #64-1877, or magnetsrc.com
1 - #30 Magnet wire 200ft, Rad. Shack 278-1345 $6.59 , or cheaper from Other Stores
1 - Miniature Lamp, 1.5V 25mA Rad. Sh. #272-1139, or All Electronics LP-3, or #48 lamp
1 - Cardboard strip, 8cm x 30.4cm
1 - Large nail, 8cm long or more
Misc. - Knife or sandpaper to strip the wires
Misc. - tape to hold wire down Optional: hand drill or electric drill to spin it (hand drill is best)
Note: if you use different parts, then it won't work.
Cheaper: 600ft wire from an open-frame solenoid from All Electronics, or Electr. Goldmine, Also:other sources of wire
First make the hollow-ended box. Score the cardboard strip like so:
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| 8cm | 3.5cm | 8cm | 3.2cm | 7.7cm |
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|8 | | | | |
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_____8_________
_|______________ \
|\ 7.7 | \ 3.5
| \3.2 | \
| \_____________|___\
| | 8 |
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| | | Fold it like this and tape
| | | it securely.
| | |
| | |
| | |
| | |
\ | |
\|__________________|
________________
_|_______________ \
|\ | \
| \ | \ Use the nail to poke a hole
| \______________|___\ perfectly straight through the
| | /| center of the box, going through
| | \ / | both sides and all three layers
| | \ / | of cardboard. Then pull the nail
| | \ (hole) | out and use it to widen all the
| | \ / | holes slightly, so when you put
| | O | the nail back through, it will
| | / \ | be a bit loose and able to spin.
| | / \ |
| | / \ | ( You can find the exact center
\ | / \ | by using a ruler to draw an "X"
\|___________________| from the corners. )
At this point you should let your four magnets clamp themselves around the nail, and give it a spin. This guarantees the box is large enough. The nail and magnets should spin freely. The corners of the magnets should NOT bump the inside of the box as they spin. If the box is a bit too small, start over and make it a little bigger. Either that, or try a thinner nail. And be sure to use the right magnets. Smaller ones won't work.
[YES, you can build the box from plexiglas or thin wood instead if you wish. However, don't make it any larger than shown above. You want the wire to stay very close to the spinning magnets, so keep the box as small as possible. And don't use smaller magnets.]
Pick the spool of number-30 magnet wire from
_______________ the kit of spools. This is the thinnest.
_|______________ \ Tape one end of the number-30 magnet wire
|\ | \ to the side of the box, then wind all of the
| \ | \ wire onto the box as shown. This gives 250
| \_____________|___\ turns. It's OK to cover up the nail hole.
| | | Pull the taped end of the wire out, then
\ | | tape down both of the wires so the coil
\\ | | doesn't unwind. You should have about 10cm
\\\====================| of wire left sticking out.
\\\====================/___
|\\====================/ \
-----+-\====================/ \
/ | ==================== \
/ | | | \ Use sandpaper or the edge of a
| \ | | | knife to scrape the thin plastic
| \|__________________| | coating off 2cm of the wire ends.
| Remove every bit of red coating,
so the wire ends are coppery.
(note: the five lines of wire shown above are not real, that's
the 'equals signs' I used to draw with. The real wire can just
be wound up in a big wad in the center of the cardboard box.)
_______________
_|______________ \
|\ | \
| \ | \
| \_____________|___\ Spread the wire away from the
| | | nail hole and tape it in place.
\ | | Stick the nail back through the
\\ | | holes and make sure it can spin.
\\\====================| Take your four magnets, stick
\\\========---=========/___ them face to face in two pairs,
|\\========(\\)========/ \ Then stick the two pairs inside
-----+-\==========(_)=======/ \ the box and on either side of the
/ | ==================== | nail so they grab the nail. Push
/ | | | | them around until they are some-
\ | | | what balanced and even, then spin
\|__________________| | the nail and see if they turn
freely. If you wish, you can
push 2cm squares of cardboard
between the magnets to straighten
them. If you wish, tape the
magnets so they don't move
around on the nail.
_____ magnets
|_____| _____________
|_____| |_____________| 2 magnets
=================|| NAIL |_____________|
|_____| ______O______
|_____| |_____________| 2 magnets
|_____________|
SIDE VIEW OF THE
NAIL AND MAGNETS VIEW FROM THE END
TWIST THE WIRES TOGETHER TO THE BULB
Make sure that each end of the generator's wires are totally cleared of red plastic coating. If there is a bit of plastic left, it might act as an insulator which turns off your light bulb circuit.Twist the scraped end of each generator wire securely around the silver tip of each wire from the small light bulb. (If necessary, use a knife to strip more plastic from the ends of the light bulb wires.) One generator wire goes to one light bulb wire, the other generator wire goes to the other light bulb wire, and the two twisted wire connections should not touch together. In the twisted wires, metal must touch metal with no plastic in between.
Spin the magnet REALLY fast and the bulb will light dimly. If it doesn't work, try spinning it in a dark room so you don't miss the dim glow. If needed, adjust the position of the magnets so they don't hit or scrape the cardboard. This thing has to spin *fast*, and if the magnets whack the cardboard and slow down, you won't see any light. (IF IT DOESN'T WORK, SEE "DEBUGGING")
Once you get it to work, try clamping the point of the nail into the chuck of a hand-crank drill. Spin the magnets fast with the drill and the bulb will light brightly. Don't go too fast or you'll burn out the bulb, or maybe fling magnets all over the room. You can try this with an electric drill as well, although electric drills don't spin as fast.
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