I'm currently using this schematic for a flyback transformer:
As you can see, there's a big problem – neither the schematic, nor the website describing it, give the value of the capacitor. It says ".01", but gives no units.
http://www.eleccircuit.com/efficient-flyback-driver-circuit-by-ic-555-irf510/ Is the website. Anyone have any ideas what the unit could be? I used a 100pF capacitor in place (since I don't have a 10mF/nF/pF). I don't know if this could be a cause.
Since I don't have any 10K potentiometers, I used 2 10K resistors instead. Not sure if this could have affected it either.
I used a large steel screw (about 8mm diameter, 8cm long), wound bifilar, for the core. I do recall something about using something straight for it, maybe I'm wrong.
The only other possibilities I can think of could be poor assembly (bad soldering or unintentional shorts), defective components, or a bad schematic.
FYI, despite my tests, it hasn't worked at all (as in absolutely no arc, not just a small one, which to me suggests the type of core isn't the cause), although there is some current flowing in it since some components have heated up (but not melted).
Anyone know which of the above factors could be the problem?
This part of the circuit is just a simple 555 astable with variable mark/space ratio.
The capacitor, along with the resistance values sets the frequency. The transistor is there to drive the mosfet which simply switches the current on and off through the primary of the transformer. The transformer steps up the voltage depending on the turns ratio.
The capacitor will be .01 microfarad (or 10nF as Andy correctly gives). By using a 100pF capacitor the oscillator will run at too high a frequency (100 times more than the original design).
I also agree with Andy that the transformer (and its design/construction) is your real problem.
My real concern about this question is that if your knowledge of electronics is this limited then building this type of circuit could be fatal. High voltage is not not an area a novice should tamper with.