Ultra-simple Electric Generator
wire and spinning magnets
©1996 William Beaty

TEST IT

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.

Note: your generator produces Alternating Current, not Direct Current. The output voltage is about 2 volts max, so there is no electric shock hazard at all.

HOW IT WORKS

When a circle of wire surrounds a magnetic field, and the magnetic field then changes, a circular "pressure" called Voltage appears. The faster the magnetic field changes, the larger the voltage becomes. This circular voltage trys to force the movable charges in the wire to rotate around the circle. In other words, moving magnets cause changing magnetic fields which try to create electric currents in closed circles of wire. A moving magnet causes a pumping action along the wire. If the circuit is not complete, if there is a break, then the pumping force won't cause any charge flow. Instead, a voltage difference will appear at the ends of the wires. But if the circuit is "complete" or "closed", then the magnet's pumping action can force the electrons of the coil to begin flowing. A moving magnet can create an electric current in a closed circuit. The effect is called Electromagnetic Induction. This is a basic law of physics, and it is used by all coil/magnet electric generators.

Generators don't have just one circle of wire. Suppose that many circles surround the moving magnet. Suppose that all the circles are connected in series to form a coil. The small voltages from all the circles will add together to give much larger voltage. A coil with 100 turns will have a hundred times more voltage than a one-turn coil.

Why is this generator AC and not DC? When the magnets flip, they create a pulse of voltage and current. But when they flip a second time, they create an opposite pulse? Yes. So then a spinning magnet is making electric signals that go plus-minus-plus-minus? Yep. It happens because, in order to create voltage and current, a magnet pole must sweep sideways across a wire. If it sweeps along a wire, nothing happens. In our little generator here, the magnet poles don't sweep constantly along the curve of the wire. Instead, first the north magnet pole sweeps across one side of the coil, and at the same time the south magnet pole sweeps backwards across the other side. The two effects add together. But next, the magnet keeps turning around, and now the opposite poles sweep across those parts of the coil. The magnet has flipped, the magnet poles are reversed, so the coil's voltage will be backwards. And if a bulb is connected, then any current will be backwards too. Each time the magnet makes one complete turn, it creates a forward pulse and then a backwards pulse. Spin the magnet fast, and it makes an alternating wave: AC.

If you want a DC generator, you'll have to add a special reversing switch to the magnet shaft. It's a switch called a "commutator." If you look up some DC generator DIY projects, you'll see how to built the commutator switch. But those generators aren't Ultra Simple!

Now for the light bulb. If we connect the ends of the coil together, then whenever the magnet moves, the metal's charges will move and a large electric current will appear in the coil. The coil gets slightly warm. What if we instead connect a light bulb between the ends of the coil? A light bulb is really just a piece of thin wire. The charges of the light bulb's filament will be pushed along. When the charges within the copper wire pass into the thin light bulb filament, their speed greatly increases. When the charges leave the filament and move back into the larger copper wire, they slow down again. Inside the narrow filament, the fast-moving charges heat the metal by a sort of electrical "friction". The metal filament gets so hot that it glows. The moving charges also heat the wires of the generator a bit, but since the generator wires are so much thicker, and since the bulb's thin filament is slowing the current throughout the entire coil, almost all of the heating takes place in the light bulb filament.

So, just connect a light bulb to a coil of wire, place a short powerful magnet in the coil, then flip the magnet fast. The faster you spin the magnet, the higher the voltage pump-force becomes, and the brighter the light bulb lights up. The more powerful your magnet, the higher the voltage and the brighter the bulb. And the more circles of wire in your coil, the higher the voltage and the brighter the bulb. In theory you should be able to light up a normal 3V flashlight bulb, but only if you can spin your magnets inhumanly fast.

OTHER THINGS TO TRY

SO WHAT?

Think of it like this. If you rub your hands together lightly, the skin stays cool, but if you rub your hands together hard, your skin gets hot. It takes more effort to rub skin hard so that it heats up; it takes work. And in a similar way, it's hard to heat the lightbulb filament, it takes work. You twist the generator shaft, the generator pushes the wire's charge through the tiny filament, and if you don't keep spinning the magnet, the magnet will be slowed quickly.

FEEL THE ELECTRONS

TURN OFF THE FIELD

MEASURE THE VOLTAGE AND CURRENT

How high can you make the voltage just by using fingers? Or using a hand drill? Try spinning the magnets just fast enough to barely light the bulb in a dark room. How small a voltage is needed? Also try disconnecting the light bulb, then measure the AC voltage across the two ends of the coil. Can you tell if it's still the same as when the bulb was connected? Hint: to spin the magnets at a constant rate, use an electric drill with a fully-charged battery. Or perhaps hook the nail to an electric motor and connect the motor to a DC power supply with settable voltage.

Note: The light bulb has around 50 ohms resistance. Also, 250ft of #30 wire has around 21 Ohms resistance. Because of the wire resistance, the generator can only create around 60 milliamps current at most (0.06 amperes.) If you wind extra #30 wire onto the generator, it will increase the maximum voltage, and maximum power. But since this adds more resistance it WON'T increase the maximum possible current. To increase the maximum possible current, either spin the magnets much faster, replace the #30 wire with thicker wire, or use a stronger type of magnet material.

MAKING DC, CHARGE A BATTERY

Convert to DC:

The hard way: add a spinning "commutator" switch and sliding metal "brushes," so that each time the magnets turn half way, the switch reverses the generator connections.

Easy way: Add a one-way valve! An "electricity valve" is called a diode or rectifier. If you connect a diode in series with one of your motor wires, it will only let the charges flow in one direction. It will change the Alternating Current into one-way flow (called "pulsating direct current.) Try diodes from Radio Shack such as 1N4000 or 1N4001. Unfortunately a diode needs about 3/4 volts to force any charges through, and this voltage subtracts from your generator output. If your generator only puts out one volt, then the diode will reduce this to 1/4 volt. So if you want to add a diode, try doubling or tripling the amount of wire on your generator. Also try using a special "Schottky" diode with lower voltage than 0.7V, such as 1N5819 from digikey.com

HISTORY OF "ULTRA SIMPLE" GENERATOR

Around 1994 I was thinking about the ultra-simple electric motor which later became known on internet as the "Beakman Motor." Wouldn't it be cool if kids could also make an electric generator that simple? But it should be possible with parts from a Radio Shack store, since Radio Shack had the special light bulb as well as magnets and spools of electromagnet wire. After a few hours of experimenting I fould that I could just barely light up the 20 milliamps bulb by using a single spool of #30 wire from radio shack. But the wire had to be VERY close to a fast spinning magnet, and the magnet had to be composed of four powerful ceramic magnets in a stack.

To impress all the Physics Teachers, I tried to make the parts be easily available, and the cost as low as possible. To make a popular project, I made sure no tools were needed except scissors. I refused to use ball bearings or plastic parts. So I made my own cardboard box for the coil, and used a nail for the spinning shaft. To avoid extra parts, the nail is just clamped by the powerful magnets. If anyone else wants to try to make a cheaper or simpler electric generator, they have to do better than I did!

MAGNET WARNING

GOING FURTHER

In the Gramme dynamo, the core 'laminations' can be made from a long length of iron wire wrapped as a hoop and doused with epoxy, tar, etc. Form a solid ring. I don't know if fine iron wire is easy to find, but barbed wire and hay baling wire is common. Or buy a toroid transformer and saw all the wire off the core? Then wrap a layer of heavy copper wire around the whole iron ring and mount this on a flywheel. Grind the outer rim flat, so the copper spiral can become its own commutator. Your non-moving stator can be permanent magnets, or non-laminated solid iron blocks, since that part is DC.

Edison's early versions used "paintbrushes" made of fine iron wire as the brushes, later replaced with blocks of slippery graphite.

But then go and do as Tesla did, during his design work for Edison corp. Convert Edison's stator designs into a compact cylinder-shape that hugs the flywheel, and includes enclosed coils rather than those extremely long horseshoe-magnets like Edison's "long legged mary anne" design.

Motor Triva: electric motors were mere lab curiosities until Zenobe Gramme developed a generator which was intended to replace battery banks, since it gave extremely smooth DC output voltage. During an inventors show, an assistant accidentally connected an unused Gramme Dynamo up to another one that was spinning under steam power. The second one started up and ran as a motor; as a *hundreds horsepower* motor. That moment was the start of the electrical age in industry. But it's not much mentioned in American Textbooks, perhaps because it would make Thomas Edison look less of a genius.

DEBUGGING

SPIN IT FAST, IN THE DARK. Sometimes your generator is working fine, but you're not spinning it fast enough. Or perhaps the dim glow of the light bulb is being missed in a brightly lit room. So, go into semi-darkness. Then spin the thing REALLY FAST. Try cranking it with an old-fashioned drill. (Electric drills don't turn very fast.) Or try gluing a tiny wheel to the nail, then rub the wheel on the spinning tire of an upside-down bicycle (don't go too fast or the bulb will burn out.)

ADD LOTS MORE WIRE. If your coil has more than 250 turns, then the bulb glows much brighter. The #30 thin spool of Radio Shack wire is 200 feet long, which gives about 250 turns. If you could wind more turns on your coil, then your bulb would light up at lower magnet speed. Buy two kits of wire from Radio Shack, then use both spools of #30. Scrape every bit of the red plastic coating off all the wire ends. Then twist the end of the new spool to the end of the old one. This creates a single longer wire. Be sure to wind the extra wire in the same direction as before.

Better source of wire: buy a large "Solenoid" from a mail order company, then use Vice-grip pliers to pry open the metal bracket. The hole in the solenoid goes through a square steel plate, and if you pry the rest of the steel frame outwards, you can remove the square plate and take out the wire spool. Peel off the tape, and wind 600 turns on your generator. DON'T USE OTHER MAGNETS, use the large 2-inch rectangular magnets sold by Radio Shack, #64-1899, see their site. Or try Educational Innovations teachersource.com, or try magnetsrc.com. They cost about $2 each, and have no holes through the center. Don't use the smaller 1 inch Radio Shack magnets. Most other magnets are way too weak and will not work unless you spin the magnets incredibly fast, at thousands of RPM (revolutions per minute.)

USING SMALLER MAGNETS
If you can't wait for mail-order of the correct magnets, instead you can use twenty of the Radio Shack 1" magnets 64-1879 Glue them together to form two large magnets.

Here's how I did it. First I formed two magnet stacks: I glued ten magnets in two separate stacks of five magnets each. I used 5-minute epoxy. Before the glue hardens, adjust the magnets so the sides of each small stack are flat, and wipe off the excess epoxy. (To make the sides flat, I laid each stack down on aluminum foil, pressed them down to align the magnets, then peeled off the foil when the glue was hard.) Next, glue two of these 5-magnet stacks together side by side so the stacks are repelling each other. See the diagram below. Glue the narrow side together, so the block will be 2" wide. Then hold them together until the glue hardens. That way the N pole of one stack is near the N pole of the other, and S is near S.

Do the same with the other ten magnets. This gives you two large rectangle magnets, each made up of ten small ones. Each magnet should have two holes on each flat pole face. Clamp the two magnets on either side of your nail as usual. They should attract together and grab the nail. These aren't as powerful as the four "high energy" ceramic magnets, so you'll need twice as much wire for your generator.

STACK THE MAGNETS SO THEY STRONGLY ATTRACT. Make sure the four rectangle magnets are stacked to create two strong poles, otherwise the generator won't work. Do this: stack up all four magnets so their widest faces are clinging together. Then jam the nail through the crack in the middle of the stack. Then take this apart, and re-assemble it inside the generator in the same way.

CLEAN THE WIRE ENDS THOROUGHLY. If the generator refuses to work, inspect the spot where the wires twist together. The coil of wire has a very thin red plastic coating, and you must clean ALL of this coating off the last half-inch of the wire ends before twisting them to the light bulb wires. Also, the tips of the light bulb wires must be stripped clean of all plastic. The metal part of the light bulb wire must touch the metal of the coil If there is any plastic between the metal of the generator wire and the light bulb wire, the circuit will be "open" and no charge will flow.

Be sure to follow the instructions and diagrams. You MUST wind the coil so the coil goes across the side of the box which has the nail hole. If you wind it so no coil is crossing the nail-hole side of the box, then the magnetic fields won't cut across the wires, and no electric voltage will be created.

Also, don't wind the coil over the open end of the box, otherwise you won't be able to get your fingers inside to make changes to the magnet.

If you cannot spin the magnets fast enough with your fingers, try a "twist drill" or hand-crank drill. Clamp the nail in the end of the drill and spin the magnets as fast as you can. An electric drill may work too, but most electric drills don't move as fast as the hand-cranked type.

AC VOLTMETER.
[WARNING, SOME DIGITAL MULTIMETERS ARE ONLY INTENDED FOR 60HZ AC, AND THEY WON'T MEASURE LOW-FREQUENCY VOLTAGE CORRECTLY. YOU'D HAVE TO SPIN THE GENERATOR FAR FASTER THAN FOUR REVS/SEC (240RPM)] If you have an electronic voltmeter, set it to measure two volts AC, then connect it to the generator wires and spin the generator. The light bulb needs a bit more than 0.50 volts AC in order to light dimly. At 1.0V it lights brightly. If your generator's voltage is lower than 0.5V, you need to spin it much faster, or you need strong magnets, or you need to add lots more turns of wire.

DON'T SUBSTITUTE THE MAGNETS OR THE LIGHT BULB WITH A DIFFERENT TYPE. It needs strong magnets and a low-voltage, low-current incandescent bulb. If your generator doesn't work, check the parts again and make sure you have the right type of magnets and the right type of light bulb. Don't use fewer magnets. Weaker magnets may work in theory, but you won't be able to spin them fast enough by hand, and a high speed motor will be required in order to spin them. Don't use an LED. A red LED could work in theory, but you need at least 1-1/2 volts to barely light one up (the green or blue kind need even higher volts.) The light bulb is better because it lights up at less than 1/2 volt. (If you really must light up an LED, use the red kind, and also add about three more spools of #30 wire to your generator coil.)

Perhaps your luck is bad and you got a dead light bulb. To test it, get any new, fresh 1.5V battery (the size doesn't matter.) Take the bulb off the generator, then touch one wire form the bulb to the top of the battery and one wire to the bottom. The light bulb should light up brightly. If it stays dark, the bulb is bad.

The generator can be improved by using more turns of wire. You used only the spool of #30 wire. With more wire, the magnets don't have to spin as fast to light the bulb. Connect the thinnest of the remaining spools of wire to one end of the wire that's already wrapped, making sure to scrape the wire ends totally clean before twisting them together. Make sure to wind the extra wire in the same direction as the rest of the coil.

Or, if you want to light your light bulb REALLY bright, buy a second kit of wire, hook the second #30 spool to the coil you have already made, then wind all the wire onto the coil. Be sure to clean all the red plastic off the ends of the extra wire that you've added.

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