Introduction: Mini Tesla Coil
A few months ago I made a small desktop Tesla Coil that was powered by a 12 volt supply. When I presented it at school, everyone acted like it was something that could only be seen in a movie. So I decided to document it here to show 'iblers that you don't need very much power to get the coil to work, it could even be powered by a battery which I did do at one point. Most people say that you need at least 5000 volts at a lot of current, but I just used an ignition coil running off a switching circuit I made. I hope that this will be useful or inspiring to anyone who wants to make their first Tesla Coil but doesn't know how to start (this is actually my second but it is built using the main parts from the first one). This was also built on an almost $0 budget since most of the parts I either had on hand or were recycled. Something cool about this is that the circuit has the option to be wired to play music very easily, but not at the best quality. Full documentation here, and my full website with all the other projects here.
Step 1: The Tesla Coil Circuit
Here is what my setup looked like (very amateur with alligator clips) and what the schematic looks like for the Tesla Coil. This is a basic spark-gap Tesla Coil with no safety features or regulators. I initially wanted a solid-state Tesla Coil, but I don't have much experience mixing high voltage and complex electronics together, so I kept it simple to see if it would work, and it did. I also designed this circuit to not need a grounding connection when in operation, but it is probably recommended to have one in there for better performance. If you do decide to include the grounding, then be careful to not use something that appliances and stuff are connected to, try to make your own grounding connection. More info on solid state TC's can be found here.
Step 2: Tesla Coil Components
Here I will list the main components and say a little about what they do.
Ignition Coil: Probably the most necessary component in a non-sstc type Tesla coil, but it doesn't have to be an ignition coil, just as long as it is something that can generate a bit of power. This is the component that supplies the high voltage that is necessary to drive the unit. If you've ever seen or used an ignition coil, you know that there is only 3 connections, which is why I had to design that isolated driver circuit so you don't get inductive kickback mixed with high voltage signals.
Spark Gap: This component is one of the main timing mechanisms. This controls when the capacitor discharges across the primary coil. A drawback of this component is that it creates a lot of light, like an arc lamp. Another drawback is that it is incredibly loud, so this complicated some things when it came to playing music off this coil. To make this one, I just used a nail in a piece of wood and a screwdriver, and the screwdriver allowed me to adjust the distance of the gap.
Capacitor: This component controls the amount of power that can surge through the spark gap and into the primary coil. It stores a charge from the transformer or ignition coil in this case. When enough power has been stored, it is released through the spark gap. So the spark gap controls the frequency and the level of the power that goes through the primary, that is why it is important to be able to adjust the length of the arc.
Primary Winding: This is the component that turns the pulses of power into somewhat strong electromagnetic energy. It creates the pulses that the secondary then amplifies. This flat coil has to work in sync with the capacitor and the spark gap to make a frequency that corresponds with the secondary winding and the topload if it has one.
Secondary Winding: This is the part that amplifies the electromagnetic pulses from the primary winding and all the other components. This unit outputs high voltage at low current (low current considering the voltage that is outputted) hence the reason you can touch the arcs made by coils of this small size. On larger Tesla coils, the voltage is high enough to let out a fairly large amount of current, so don't try touching too big of arcs. These also output a lot of electromagnetic energy so try not to let any electronics nearby, and on larger coils, unplug anything that is connected to the wall outlet unless the coil has it's own isolated power supply which I have never seen on large coils, only on small ones.
Step 3: The Driver Circuit
I designed my own driver circuit because all of the other ones for driving an ignition coil kept killing all of my 555 timers. This happened because high voltage from the coil's negative contact surged through and backfired into the driver circuit which literally fried any 555 timer that was hooked up to it. I had to go through 7 different 555's to get this to work fairly flawlessly. I desoldered a few IC's from old circuit boards and figured out that they were mostly photocouplers, then it hit me that I could use these to isolate the signal from the 555 timer from the transistor and coil. In my case, I desoldered a few Cosmo 1010 photocouplers and used those, but any isolator would work as long as it could carry the signal and keep the 2 parts isolated. The transistor I pulled out of what appeared to be an old power supply. By playing with the capacitor and resistor values, you can change the frequency of the arc but the ones in the schematic seemed to work best for me. The ignition coil is not portrayed as connected to the driver circuit, but it is shown clearly where to connect in the schematic of the Tesla Coil itself. It is also essential that the 6 volt power source is separate from the 12 volt one, that is why there's a photocoupler, to completely isolate it. You can see that there is an "audio in" port on pin 5 of the 555 timer, that is optional, but in order to use it, you will have to change the capacitor from a 0.47uF electrolytic to a 0.1uF ceramic capacitor (it's the one with the number 104); all you have to do is connect the output of the audio device to this and connect the common wire to the negative on the 6 volt side, but try not to use anything expensive as I've been using a cheap CD player and it acts a bit weird now from being connected, so try not to use your $200 ipod touch or anything like that. By the way, this can be powered by two batteries, one 9 volt for the 555 circuit and one 12 volt or two 6 volts for the coil power supply.
Step 4: Action Photos
Here are some action photos of my tiny Tesla coil, I'm surprised that my iTouch didn't get fried, but on the videos you can see a little distortion. The first 2 pictures are the streamers going through a standard 60 watt argon filled incandescent light bulb. The last 2 pictures are a CFL without the circuitry and base, but there is enough electromagnetism going through the air to excite the phosphor in the bulb... wireless lighting.
Step 5: Videos of the Tesla Coil
I hope this helps someone to get started with Tesla Coils and high voltage. Thanks for reading.
Step 6: Disclaimers
For legal reasons this boring part has to be here.
This is playing with high voltage, be safe.
If you hurt and/or kill yourself replicating this, it's not my fault.
If you are going to copy this info or whatever, then just give me credit somewhere (or 25% if you make money :) )
If you use the information in this site to kill yourself, your friends, family members, acquaintances, total strangers, pets, electronic devices or burn down your house, it is not my problem.
Blah blah blah legal-stuff legal-stuff.