Well, again don’t zap anyone with this. You can make other useful devices with this design such as ignitor, a noisy-sparky-dim-inefficient light bulb, scary Halloween costume, or whatever you can imagine! Just don’t hurt each other. So like mentioned in the video you can use a transformer to create very high voltage. Creating very high voltage without a transformer can be very hard, because you would need very high voltage rated components on the output (>10000V), while with a transformer you can pick lower voltage rating components on the low voltage side and let the transformer take care of creating the high voltage.

But how does a transformer work? I make it simple here: a typical transformer is made of two wire windings around the same core (air, metal, ferrite, etc.).

When you apply AC voltage on one side, you create magnetic field which passes through both windings. Now changes in magnetic field will move electrons on the secondary and hence create current flow. You need change in magnetic field to move electrons back and forth, and so transformers only work with alternating signals. They don’t need to be sine wave, but changing in general. Now in an ideal transformer the output to input voltage ratio is equal to output winding to input winding number of turns, like I showed in the picture below (60 if for my specific transformer). Ignition Coil Winding On the other hand, the output to input current ratio it proportional to input winding number of turns to the output, which is backwards the voltage ratio. As you know power is voltage times current and if you combine these together you will realize that in an ideal transformer (100% efficient) the input power is equal to output power.

Of course in real life there are many losses that will reduce the efficiency such as core losses in form of heat, wire resistive losses, etc Like shown in the figure above in a car ignition coil one side of the primary and secondary windings is tied together, which doesn’t change the behavior of the transformer. It reduces the number of connections to the coil, but also eliminates the primary to secondary isolation that is not needed here, but is critical in many other applications such as isolated power converters.

So like a regular transformer, if I put 10VAC on the primary of this specific transformer with 60:1 secondary to primary winding ratio, I will get close to 600VAC. But for a taser I need over 10000V on the output and that’s why I use a useful behavior of the inductor. Unlike a capacitor that tried as hard as it can to keep the voltage across if as stable as possible by sourcing and sinking surges of current, the inductor tries to keep its current stable as much as it can, by surging the voltage across it. So if you charge it to a certain current, it tries to not allow or slowly change the current. What does that do for us?

Take a look at the circuit below. At the beginning the current through the inductor L1 is zero. When we close the switch, the inductor slowly allows the current to rise through V+ supply. Say it rises to 1A and then we open the switch.

It's 555 timer based and what it's for is for driving ignition coils. You can use the circuit for testing ignition. I took a very common design (a 555 timer driving a MOSFET) and built it. Well, more like lashed it up. As seen in photo. In the photo, it shows the initial setup with two ignition coils. The sparks in the photos below are from one ignition coil only however. I consider the circuitry used here quite unsophisticated, and I have.

But the inductor wants to continue driving 1A current. So what happens is that it pushed the current through D1, which was off up to this point and turns it on, and the current runs through R1 resistor. Now let’s say R1 is 1kOhm.

So 1A x 1k = 1000V is generated across the resistor in form of a spike that dissipates quickly. Sumangali Tv Serial Actor Pradeep on this page. So just that easily, we created 1kV spike. This means that the voltage across the inductor on the diode side jumped close to 1000V, all in order to continue outputting 1A.This circuit is the basic concept behind the voltage booster circuits. Just be aware that if you generate huge voltages, all your components such as the inductor, switch, diode and resistor should be able to handle and not break under such voltages. Now the primary of the transformer is the same as an inductor, it has self inductance. If we charge it and let go like I mentioned, the voltage would spike up and that converts to even higher voltage on the secondary. My specific car ignition coil has a 0.7Ohm primary winding resistance.

So if I put 12V across it, I would have 17A through hit. That is beyond my supply and battery limit and so pulls their voltages down to a lower level which is still OK. For example with the power supply, I can’t run more than 10A.