http://info.ee.surrey.ac.uk/Workshop/adv...
http://www.angelfire.com/electronic/funw...
http://www.hamuniverse.com/k4mmgcoilwind...
http://www.coilgun.info/mark1/windingcoi...
Consider using an ignition coil from a car. You can get one for cheap at a breakers yard, and it runs from 12 volts.
An interesting project would be to measure the actual voltage of the "6.8 million volt stun gun" below, which is an induction coil. 6.8 MV would make a spark over 7 feet long!
The second link is how to build a 75kV induction coil. You could fairly easily soup it up to, say, 500kV if you want a more impresive spark. The schematic is the same, you would just need to change a few component values.
The link includes safety information, which is, of course, an important part of any project.
The safety warning is appropriate as you failed to tell us the specs of the induction coil you need. A junked TV has about 100 of them. More likely you want 1000 volts for a millisecond or two. A large motor or large transformer will usually work. Connect a half dead penlight cell for a fraction of a second to various wire or terminal combinations. A spark when you disconnect means you have found a useful combination. The voltage pulse may also be present on other terminals. A big 12 volt battery will likely also work but the voltage pulse may kill you, so be careful. A magnetic field is produced which collapses when you disconnect causing the coil voltage to rise much higher than the battery voltage for a millisecond or two Neil
Do NOT DO IT if you do not know the theory part of electricity. Household electricity can cause blown out fuses and can electrocute and kill you, if you do not know what you are doing.
Even pen-cell batteries can heat up and explode or cause a fire and burn severely if they are short circuited and if they do not meet enough resistance in the circuit.
Be warned. Take help from someone who knows it all.
i want to make an induction coil for a project, at the minimum cost.
