[ad#Google links]Shakeable Dynamo Part 1: Why bother?
Firstly, there is no such thing as ‘free energy‘ you have to always put something in to get something out. I call this free energy because it comes from your own movements rather than having to pay cash for a battery or the juice to charge it, I guess it’s better to call it ‘financially free energy’. Also when you look at this, some of you may point out that this isn’t a dynamo because it generates AC current, but I call it a dynamo because of the bridge rectifier built in to that converts this to DC.
Basically like all alternators and dynamos it works on the principle of converting mechanical energy into electrical energy by inducing current in a conducting medium, such as copper wire, using a magnetic field. Typically this is done by rotating a magnet inside coils of wire.
My alternator works in much the same way – we move a magnet through a coil of wire to induce a current, only we do this in a linear motion rather than circular. There are lots of crazy equations out there that state how much current you will get from a magnet of certain strength, a certain number of coils of wire of a certain thickness etc…
Mine is much much simpler – I first did a very small test to check that the principle worked, with only a few coils I got a current. Then I just kept winding until I got to a certain thickness and invariably got bored! My windings weren’t at all neat and were all over the place, so if my bodge job worked a more precise version will work better (probably).
So the main question arises – how much current can I get out of the smallest amount of wire and magnets. My aim was to build something to the thickness of an AA battery.
Ok, lets look at all the parts you’ll need, it’s actually not that many and for your magnets and wire – get it off ebay, you’ll get far more for far less than from buying them from a retailer.
What you need to build a simple dynamo / alternator
- 1 biro or piece of tubing with a 6mm diameter cut to roughly 10cm in length, the magnets will need to slide freely down the tube
- At least 3 neodymium (rare earth, super strong) circular magnets with a diameter of 6mm – you can buy a set of 50 for not very much – these are really strong so be careful
- Magnet/ winding wire around a 32-42 AWG, thinner wire (42 AWG) means more coils
- 4 ‘N’ series rectifier diodes – any will work fine for our low voltage most of the 1n series have the same voltage drop – I used 1n004’s
- Some hookup wire – around 18-22 AWG (any wire will do really) for soldering the magnet wire to and building the circuit.
- An LED (for testing)
- Soldering iron & solder
- Breadboard – useful to build the bridge rectifier and test the dynamo
- Cutters & wire strippers
- Also handy to have a multimeter to check the output and a couple of screwdrivers or sticks to help spool the wire
- Some clingfilm and electrical tape
So lets build it step by step with my photos, at the end of this you’ll have the basic dynamo, Step 4 at the bottom will show you how to build the rectifier and the theory behind that.
How to build the alternator
First check that your magnets slide easily through your tube, you may need a few connected together to stop them spinning inside or getting stuck.
Now get your tubing or pen and cut it to size, about 10cm in length
Next we need to add some ‘guides’ so that we can keep our coils in place on the pen, I used a square of cardboard from a box taped on the ends
Now the fun part, winding the coils. First don’t bother taping down the end of the wire, instead make a small cut in one of the guides and use this to hold the wire in place as you wind – you need to be able to get to both ends of the wire later on! You’ll need to save about 5-10cm.
The easiest way to coil the wire would be do use a drill or something to spin the tube, taking wire off the reel, but this wire is so thin that if it gets snagged it will snap and you have to start all over again. Best to do it by hand and watch some TV as you do it, it doesn’t take that long just stick your tube over the a screw driver so you can spin it and stick the reel onto something like a drum stick.
With the reels stick on your lap, the reel between your legs, you can now hold the tube and spin it on the screwdriver to wind the coils and keep a fairly good tension. If you want to be precise then you can wind the coils accurately or like me just wind away in any fashion.
I kept winding until my coils got to the thickness of an AA battery, so a diameter of about 12mm – took a while but after a while it gets easy, especially if you’re not fussed on how well it’s wound.
Next we take 2 pieces of our hookup wire, remove the casing on either end and then wrap one end of the copper magnet wire to one end of each wire, you’ll need several coils around this wire.
Now get out that soldering iron and get it heated up, the heat of the solder on the ends of the wire will melt away the very thin varnish on the copper magnet wire while it also binds it to the hook up wire. Be careful as the thin wire will snap very easily and you’ll need to repeat this step.
Before we go further you may want to check that the connections are good with a multimeter set to measure continuity. As long as there is some fluctuation in the initial reading all is good. You can see that I’ve temporarily secured my magnet wire to the guides. This is also a good time if you want to measure the current generated when your magnets pass through the tube / pen.
And thats it, shake the magnets inside the tube to generate a current the basic alternator is built, you can hook that up to a breadboard to play with, if you add an LED and shake the generator you’ll see the LED light up, it’ll be quite dim and no matter how fast you shake the magnets, the LED doesn’t remain consistantly powered, this is because the current is alternating and an LED require direct current instead.
Once you’re happy and understand whats happening we can proceed to step 3 which improves up on the blinking LED and gives you a current you can actually use.
Shakeable Dynamo Part 3: How electromagnetic induction works
Shakeable Dynamo Part 4: Building the bridge rectifier