Here is a shopping list of parts required for the circuit:
1 x 2N3055 Transistor
This is an NPN type transistor - Cost approx. £1.50 / €2.50 / $3.00
1 x 1N4001 Diode
(Silicone Fast Switching Diode) - Cost approx. £0.20 / €0.30 / $0.40
1 x 1N4007 Diode
(Silicone Fast Switching Diode) - Cost approx. £0.20 / €0.30 / $0.40
1 x 100 ohm resistor
(at least 1/4 watt but I would recommend 1/2 watt) - Cost approx. £0.20 / €0.30 / $0.40
1 x 1 kilo ohm linear potentiometer
(the higher the wattage the better. Carbon track should be fine.)
1 x Neon Bulb
(NE2 type - wire ended)
Approx. 250g of Enamel Coated 22swg Copper Wire (Magnet Wire)
Cost approx. £6.50 / €8.20 / $12.90
Approx. 250g of Enamel Coated 26swg Copper Wire (Magnet Wire)
Cost approx. £6.50 / €8.20 / $12.90
Approx 2 meters of High Current Wire
This should be more than enough to hook up the batteries - Cost approx. £6.50 / €8.20 / $12.90
The Core
You will also need to use something for your core. Personally, I use iron filings mixed with glue and I am satisfied with the results. However John Bedini recommends using welding rods (0.042" inch diameter copper coated steel rod). You can then bang in as many welding rods as will fill your core. Each of the rods must be electrically insulated from eachother. Most people will let the rods rust for a while, though you can coat them with a genorous layer of nail varnish.... or both... I think there is more siginicance to letting the rods rust but not sure what it is... perhaps someone else can enlighten us!
What you don't want to use for the core is solid iron or steel. One of the key mechanisms to the operation of the ssg is the fast switching of the magnetic field and if you use a solid mass for your core it is likely to create eddy currents that disrupt and prolong the degredation of the magnetic field.
Steel bolts are particularly bad as they retain their magnetism... like when you leave a paper clip on a magnet for a short while you will find the paper clip can attract other paper clips.
Which brings us onto the MAGNETS!
Although several people have reported positive results using Neodymium or Rare Earth Magnets, it is not recommended to use those.
One of the main problems with using extremely strong magnets is that whatever core you are using, it is likey to become magnetic if it is under prolonged exposure to these magnets.
sooooo.... use Ceramics!!! On a small rotor (about the size of a hard drive) you should be ok using 20mm x 10mm x 5mm ceramic magnets. On a rotor the size of a bike wheel you will need larger magnets approx. 50mm x 25mm x 10mm. If you find the magnets are too weak you can always double stack them.
I bought 100 20mm x 10mm x 5mm magnets for about £10 / €15 / $20 which is far more than I need, but like everything listed here, it is good to have spares!
On to the rotor....
There is a large variety of rotors you can use! The most commonly used it an alluminium bike wheel (alluminium is important... NOT steel)... you should be able to fit about 24 magnets to a standard bike wheel and achieve speeds around 200 - 300rpm.
Alot of people also use discraded hard drives... these seem to work well and you should be able to fit about 6 magnets to it and achieve speeds around 1500 - 2000 rpm
I am using a tape head I salvaged from an old VCR. I think it's great! The bearings are very smooth and you can easily mount it on another surface. You will be looking at speeds around 2500rpm and higher. Again, about 6 small magnets should fit comfortably on a rotor this size.
Going even small still, the original schoolgirl motor used a rollerskate wheel with 4 magnets attached to it... Roller blade wheels are probably better. The bearings in these are very good quality and should be able to reach between 3000 - 4000 rpm.
All these speeds are approximation and can vary... don't force your motor to get to these speeds. If you feel the sweet spot is slower then don't push it to go faster.
hmmmm.... that pretty much covers all the parts you will need! You will have to improvise with a framework to mount the ssg and if you don't have an empty spool lying around, again, you will have to improvise.
Batteries
These can be the most expensive part of the set up. For a small motor you may be able to get away with using 1.3ah (amp hour) 12volt Lead Acid Batteries though I would recommend getting at least 7 amp hour batteries. You want the batteries to be big enough so that the motor runs at the "C20 Rate". The Ah of a battery is the amount of amps the battery can supply for one hour... though this is far too high a current for the batteries to supply and will damage them quickly. This is why we use the C20 Rate which is the Amp Hour rating of the battery divided by 20...
for example if your motor is running on 300ma you need a battery that is at least 6 amp hours (0.3 x 20 = 6). Or, to look at it another way, if your battery is rated at 7 amp hours, you shouldn't discharge the battery with more than 350ma (7 / 20 = 350).
a 1.3ah 12v Lead Acid Battery can cost around £12 / €18 / $24
a 7ah 12v Lead Acid Battery can cost around £15 / €22 / $30
a 24ah 12v Lead Acid Battery can cost around £40 / €60 / $80
You will need at least 2 equal sized batteries. These prices are estimates. You should be able to find somewhere that will give you a deal if you buy more than one battery.
Equipment you will need.
At least 1 Multimeter. Digital is ok, though we are using pulse DC in the SSG so when measuring the amps it is highly recommended to use an Analogue Amp Meter that goes up to 1 amp or more. You will need the meters to measure your input amps as well as your battery voltages.
A Laser Tachometer. A laser tachometer measures the rpm of your motor. It is not a neccessary tool when you are starting out but you will be very glad to have one as it benefits fine tuning and you will need it to make an accurate record of your motor's performance.
Soldering Iron... to solder the circuit... kind of goes without saying! The circuit will still operate if the connections aren't soldered though once you are sure it is wired correctly you should solder all the connections.
Where to find all this stuff???
Lead Acid Batteries ->
http://shop.eurobatteries.com/index.php?cPath=25_62
Components ->
http://www.maplin.co.uk/
http://www.radioshack.com/
Magnets ->
http://e-magnetsuk.com/magnet_products/ ... gnets.aspx
Most of these companies are UK Based... If anyone would like to provide additional sources for their country feel free to post!
all the best!
Seph

