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The lunatic progress of the computer industry means that there are enormous numbers of small stepper motors in rubbish - most printers contain at least two. Larger ones from really big dot matrix and some laser printers can be used as small electricity generators, capable of outputs between several and twenty Watts. (See the page on steppers as generators) There are also great quantities of smaller ones which are not able to generate a really useful amount of power. On the other hand, they are made to a high quality standard and can operate effectively at very low rotation rates, so it's tempting to find things to do with them.
While using a small motor to show some people how steppers could be used as generators, I made up a coloured LED display to demonstrate its multi-phase output. We quickly realised its decorative potential, and I went on to make an improved version which used a discarded plastic car hub disc to mount the motor and the LED's. When the disc is spun with the spindle held still, the LED's come on in a stationary pattern determined by the magnetic pattern in the motor's rotor. All the power to light the LED's is generated by  the motion, and the circuit couldn't be simpler - you just connect them to the various outputs from the motor. You don't need the series resistors normally used in LED circuits as small steppers have quite a high resistance in their windings, and providing the LED's are wired in parallel in opposite facing pairs they will run happily on the AC outputs from the motor.

The pattern you get is to some extent set by the design of the motor, but creative input can be applied in the layout and colour of the LEDs. Although maybe 75% of the motors available are of one type, a bit of searching about will produce more interesting ones capable of a variety of intricate patterns. They're not all that bright but are ideal for use at night or in dark rooms such as at a party or chillout room. As they can be made almost entirely from recycled items and run on renewable energy, they are a nice Green alternative to small fireworks. Although they don't produce any useable energy, they're good as an entry to DIY Green energy and recycling art. They're small enough to be made on a corner of the kitchen table and don't produce high enough voltages or currents to be an electrical hazard.

HOW TO DO IT
Tools needed: Soldering Iron (and Solder), Pointy Pliers, Wire Cutters, Hand Drill and Bits, Scriber or other sharp pointed thing for marking, various small tools to dismantle printer, basic Digital Voltmeter.
Materials needed: A scrapped printer to get motors and other bits out of, at least one old car hub disc, about 8 LED's for instance Maplin WL27 and WL28, some 20swg/0.9mm tinned copper wire for instance Maplin BL13, some kind of knob or handle to stick on the motor spindle, try a cotton reel or a knob off the printer. An experienced recycler should be able to get nearly all the bits from rubbish but if you're stuck have a look at www.maplin.co.uk

To make your first decorative twirly disc, you're better off getting one of the common motors. They have 48 steps per revolution (7.5 degrees per step) and about 4cm diameter is an ideal size though larger flat ones from daisywheel printers are also good. Try to find one with a sturdy spindle as that's got to support the whole assembly later.
The first thing to do is probably the most technically difficult, though it's not that bad. The problem is to identify the group of either five or six wires coming out (If your motor has got less or more wires, put it on one side for later and get a simpler one, you won't have to look very far). You will need to use a digital voltmeter set to the Resistance (Ohms) range. You can cut off any plug on the end of the wires, but leave them as long as possible.

Six wire ones are usually easy to sort out. For a start they're usually fairly obviously divided into two sections with separate sets of three wires. The sections have no connection to each other - it's like two motors on the same shaft. In each set of three, one is the middle and the other two are opposite ends of a coil. Try measuring the resistance between different pairs of wires. The resistance from the middle to either of the ends will be the same, and the reading across the ends will be twice as much, like this. It doesn't matter what the readings actually are, and you don't have to know what they mean.
Five wire ones are also easy; basically they're just six wire ones where the middles of both windings have been connected internally. There are four windings which are all connected at one end. You may be able to work out which is which just by looking at the motor. If not you'll have to use the resistance meter as above. Just poke about on different pairs of wires; you'll find some readings you get are exactly half the size of others. When you get a half reading, one of the wires you're on is the common, so just move the probes one at a time to find which one it is.

Next you need to do a test to find out roughly what the motor is capable of. Get a couple of LED's and just temporarily connect them back to back (cathode of one to anode of the other - it doesn't matter if you can't remember which is which, just make sure they're facing opposite ways.) across one of the windings you've just found. In case you've never looked closely at LED's before, here's how to tell which way around they are. Keep the wires and the LED's leads as long as possible for the moment. If this is one of your first attempts at soldering, use a pair of pliers with an elastic band round the handles clamped to the LED leads to keep the heat away. Hold the motor by its spindle and spin the body, being careful not to hit yourself in the eye with either the LED's or the trailing wires from the other windings! In your first go, this just indicates whether the motor is suitable or not; as you get more experienced you can use it to work out things like the density of the LED dots so you can put them on the disc in clever patterns.
You should find that you get a nice ring of light blobs with the LED's coming on alternately as the power goes alternately plus and minus. (That's why you have to wire the LED's in pairs, each one limits the minus power across the other one.). If you find that nothing happens unless you spin it really fast, try another motor - there's usually at least two per printer.

Having established that you've got a suitable motor, you'll need something disc shaped to mount it on. Old car hub discs from the side of the road are ideal; they're about the right weight for keeping it going for a while and there is usually a moulding pip on the inside which gives an accurate centre marker. Unfortunately the discs are usually in a really nasty filthy condition when you get them. Scrub them thoroughly with hot soapy water preferably outdoors and with hand protection. Do not wire brush or vacuum them in case there's any asbestos dust. Asbestos hasn't been used in most car brakes for years but you can never be too careful with stuff like that! Once you've cleaned the disc, take off any locating clips and other sticking out bits; ideally use coarse sandpaper to smooth down the back so it can't cut you when it's spinning. If bits of the outside are cracked, you may be able to cut it down and just use the middle. Mark the centre of the disc as accurately as you can, then use it to mark the positions for the LED's and the motor fixing holes. Once you've done that you need to drill a large hole at the centre for the spindle to go through. If the spindle's very short you may have to do something like cutting a large enough hole to have the whole motor sticking through the disc so you've got enough room to put a handle or knob on the spindle.

Either a six wire or five wire motor is at least capable of powering eight LED's in four pairs. If you've got the time you could unsolder LED's from scrap display boards, but they only cost about 7p from Maplin's. If you get the standard 5mm ones and drill 5mm holes in the disc carefully with a hand drill, you should find they are a push fit and don't even need any glue. For your first disc, it's probably best to go for all the LED's in a single line or maybe two opposite lines of four. If you go for the two lines you should find that you can make the two groups either interleave or coincide by swapping the wires about. If you put all eight LED's in one line you might have to do something like putting a small weight like a nut and bolt opposite to rebalance the disc.

A group of four LED's should be wired to a pair of coils like this. Note that the LED layout was changed on 9th October 2005. It used to look like this so may be different to one you've got on a leaflet. Both circuits work OK; the reason for the change is that the new one looks simpler and is easier to build. It's best to wire up the LED's on the disc first without connecting the motor wires, then try connecting the coils to them different ways around, still keeping the motor wires long until you've got a pattern you like. It doesn't matter if you spin the motor with some of the coils disconnected while you're experimenting. The only way you might damage anything would be by connecting an LED on its own without an opposite facing one in parallel, or by overcooking them with the soldering iron. Once you've found a good combination, you can cut the wires shorter and fix them to the back of the disc. I often use thin single core bare wire and fix it down to the disc by melting it in carefully with a soldering iron, but for safety I don't suggest you should do it that way because of the plastic fumes!

Once you've got a working disc, you'll need a better way of holding it than just gripping the motor spindle or gear in your fingers. If you haven't got access to metalwork facilities, knobs from old radios or hifi equipment with grubscrew fixing work quite well. If the motor has a gear on it which is just a bit too big to go in, file the teeth down or take out the grubscrew and drill out the hole slightly. Another idea is to put a short piece of plastic tube over the gear or spindle and force a cotton reel over it or maybe a knob from a scrapped printer.

That's it, really. If you can follow the above you should be able to make a basic hub disc twirly thing using one of the common 48 step motors.

Once you've got bored with that, you can start collecting different motors and doing some more advanced designs.
The common motors are rated at between 5 and 12 Volts so will power LED's needing 2 Volts at low speeds. If you can find a motor with a higher voltage rating such as 24 Volts, it's capable of lighting chains of LED's in series. In fact even if you've got a 12 Volt one it may be worth trying it. To find out if it is, try the basic test as before, but put two pairs of LED's in a series chain and see if they will light up. Once you've found out it works, there's a neat trick you can do to make the LED pattern more interesting. If you put a resistor in parallel with one of the LED pairs, say about a thousand Ohms (1k), like this, what happens is that at low speeds, only the other set of LED's lights as the voltage across the resistor is below 2 Volts. At higher speeds, enough current flows through the lit LED's to bring the voltage across the resistor (and the first set of LED's) up to 2V so that both sets light up. To start off with, they will only show as dots, but as you increase the speed more the dots will lengthen to lines like the other set. It's not much more complicated to wire up than the standard version, all you do is add another set of LED's and four resistors. Here's another example. The exact size of the resistors isn't critical - you might even be able to find four the same size in one of the printers you've scrapped for the motors. If the resistance is too high the first set of LED's won't light up very brightly, and if it's too low the second set won't light up until the disc's spinning really  fast.

Another variation makes use of the very low voltage motors found in some equipment such as more recent laser printers and paper shredders. At first sight they don't look all that suitable as they've often only got two windings terminating in four wires. This type of motor often has quite a low resistance in each winding, typically less than ten Ohms, and a much larger number of steps per revolution, sometimes two or four hundred. Each winding of these motors is typically capable of powering as many as eight LED's connected in two parallel groups of four like this. Here's a small one with four LED's per winding. You can't make the LED patterns as complex as the type of motor with four windings, but what they lack in complexity they make up for in density. Here's what a bigger one with 18 LED's looks like. Again, if you've got one of these, do the basic test and try adding on more and more parallel sets of LED's until the brightness starts to drop off. If you've got one of the really high resolution motors, you may have to try using 3 mm LED's instead of 5 mm to stop the bright dots merging into one another near the centre of the disc. If you do use a lot of LED's, you need to get a fairly heavy hub disc otherwise the power taken by all the LED's will slow it down too quickly. When mounting the LED's on the disc, it's best to wire next door LED's opposite ways around so that the bright dots interleave.

More modern inkjet printers such as Canon BJ's have really tiny motors in them - they're too small to support the weight of a whole hub disc but quite capable of lighting eight or so LED's at a good brightness. All you've got to do is match them to a suitably small plastic disc. Lids of plastic containers (or CD's) often haven't got the weight to store enough energy. However it's possible to make some really effective pocket sized discs using the very middles of hub discs whose outsides have been trashed by being run over, or discs cut out of the cases of larger printers or computer base units using a compass to mark them out.

The possibilities for this type of self powered decoration are still being expanded - a couple of people have already produced illuminated windmills using things like old car radiator fans with a stepper in the middle. Another interesting one is a thing like a short bit of LED rope light attached to an arm on the side of a motor so that the light pulses appear in space when it is whirled around. It's your turn next! There's plenty of scope for experimenting - the power produced by stepper motors is nowhere near high enough to either give a shock or burn out wires. The worst mishap you could have would be to destroy a few pence worth of LED by putting too much voltage across it backwards by not connecting a reverse one before you spin the motor or just melting it while soldering.

Good Luck!