Building a Solid State Tesla Coil Using the SparkFun Pro Micro and Arduino Nano

As I began to build my solid state Tesla coil using the SparkFun Pro Micro and Arduino Nano, I decided to start by creating a circuit that would hold the high voltage capacitors. I placed 1x 2.5mm spark gap holds in the perf board, which held the igbts, with one side of each being connected to the negative terminal of the capacitor. The other side was connected to the negative terminal of the capacitor and then to the other negative terminal of the capacitor through a small piece of wire. This was done because the spark gaps needed two terminals to hold them together.

Once I was certain that all igbts fit on the perf board, I removed them again and labeled each pin according to the pin out of the igbt. I did this because it saved me a bit of confusion while I continued by soldering the rest of the complimentary power electronic components in place once that was done. This included the voltage regulator and capacitors which were necessary for creating the high voltage required for the Tesla coil.

The next step was to create the control circuit, which started off with the voltage regulator and capacitors, followed by the IC sockets, Arduino Nano sockets, 555 timer oscillator, Schmid trigger, and finally the two mosfet drivers. For most part I tried to use silver carrier wire for the connections but eventually had to utilize a bit of stiff hookup wire.

After around 5 hours the circuit was complete and it was time to connect the control circuit to a 15v power source once I was sure that all the voltages at the IC sockets were correct. I inserted the ic's push the igbts with heat sing in their rightful place and connected them to the Circuit for first test.

I hooked up the Power Electronics to 15 volt power source as well and measured the voltage at the flyback diodes which presented us with a targeted Square wave and by attaching a proper loads to the inverter the voltage spikes also decrease significantly which means that the circuit works fine so I removed the wires of the primary coil from the olden inverter sold a 210 AWG wires to the new inverter and sold the primary wires to them as a power source.

I used a lap bench power supply with a maximum output voltage of 30 volts and a maximum current output of 20 amps after connecting its output to the input of the inverter and adding a piece of silver copper wire to the topload it was time for proper test. I added an input voltage of 8 volts and a frequency of around 60 kHz the primary coil around 4.5 amps and thus created pretty decent arcs and lighted up CCF lamps without a problem.

However, what was noticeable while playing around with the Tesla coil was that the temperature of the igbts rose up to 50° C and Beyond even though we only used 8 volts on the inputs to fix that. You usually utilize an interruptor which is in my case the Arduino it's D5 pin directly connects to the SD or shutdown pin of the mosfet drivers and turns them off completely if D5 is high or turns the drivers on if the five is low.

To further improve the stability of the arc, I added two potentiometers to the A1 and A5 pin of the Arduino and wrote a bit of code that utilizes the time zero registers we can output a pwm signal whose frequency and duty cycle is controllable through the potentiometers. The PWM signal lies between 30 HZ and 1 kHz and obviously between 0% and 100% duty cycle. This way we can still create the same arc as before but it only requires half the power or even less.

The last challenge that I have to face is that while creating arcs, the resonance frequency of the secondary changes a bit which is not only visible on the oscilloscope but also debases the energy transfer. I originally planned to include a feedback Transformer on the secondary which supplies the resonance frequency to the mosfet drivers I even had jumpers to switch between the 55 timer and the feedback signal.

The oscillator without the 55 timer did not want it to start on its own so I will have to fix this problem for the final chapter of this project. All we can do for now is setting the duty cycle to 75% cranking up the input voltage to 30 volts and have fun with a so far untuned solid state Tesla coil which are already pretty scary anyway.

I hope you enjoyed this project so far if so don't forget to like share and subscribe stay creative and I will see you next time.

WEBVTTKind: captionsLanguage: enduring the previous part of the Tesla coil project we found out that by utilizing an inverter circuit and fine-tuning its rectangular output voltage to the resonance frequency of the secondary coil so just above 400 khz the power consumption of the primary rapidly increased and we successfully induced the high voltage into the secondary so with those guidelines in mind I designed a new more powerful full Bridge inverter circuit the reason why I chose a more complicated full Bridge with four transistors instead of the simple half Bridge with only two transistors is that by applying for example 30 volts DC the half Bridge can only create positive and negative 15 volts across our primary coil while the full Bridge can utilize the complete Supply voltage and does obviously can generate bigger arcs for the transistors I went with igbts IRG p50 b60 PD ons to be specific only problem is that such igbts only feature medium fast switching times which can be a problem since we're dealing with a resonance frequency above 400 khz so to decrease it I got myself an aluminum air duct from the home improvement store after stretching it out and cutting off a fitting length I used an adapter piece to form a donut shape with it to hold this form permanently though I mixed up quite a bit of two compon adhesive applied it generously to the adapter and push the air duct onto it in order to mount this top load and create an elevated platform for the Tesla coil I then marked a 24x 24 cm square onto two pieces of Beach plywoods and used the circle orur to create both shapes next I marked Four Points in the edges of one square plywood piece and used the 4 mm drill bits to drill the holes near the edges I then used this plywood piece as a template to Mark the necessary holes onto the other plywood piece and drilled the four holes through it as well to finish the square shapes for now I marked the center point on one of them and dwelled a hole there before I continued by utilizing Compass to Mark a circle with a diameter of 7 cm onto another piece of plywoods through the help of my scroll saw I cut out the circle shape and used the 4 mm drill bits once again to create a hole in the center of it at this point I spray painted the square and circle plywood pieces black and moved on by utilizing my handsaw to create a shorter piece of the spa from the previous episodes with a length of 31.5 cm and after drilling a 3mm hole in the center of The Spar from both sides it was finally assembly time I started by using an M4 wood screw to secure the square plywood piece with the center hole to The Spar then I used 10 cm long bro spacers and M4 screws near the edges of the plywood pieces to mount them to one another after positioning the secondary coil on top of the platform I drilled a 1 mm hole next to it so that its ground wire can be pushed through once I then slid on the primary coil it was time to position the topl load and secure it in place with a circle plywood piece and an additional M4 wood screw last but not least I directed the output wire of the secondary coil to the topload and connected them through a solder connection and through this design choice we successfully lowered the resonance frequency of the Tesla coil down to around 100 70 khz which means it is now time to have a closer look at the new circuit schematic I will be using an input voltage of 15 volts which will then be lowered by voltage Regulators to 5 volts and 12 volts for the control circuit the 555 timer acts as an oscillator and creates a pwm signal with a duty cycle of 50% and a variable frequency from 40 khz up to 600 khz this signal then connects to the high input of the left igp driver and the low input of the right igp driver so that the top left and down right igps turn on at the same time additionally this signal is inverted by Schmid trigger which then supplies the inverted signal to the low end of the left driver and the high end of the right driver so that the other two igbts turn on after the first two turned off and since the igbt are rated for up to 600 volts it should be possible to supply rectified Mains voltage to them then there are also bootstrap diodes and capacitors gate diodes and resistors flyback diodes as well as pull down resistors and Xena diodes for safety what I'm trying to say with that is that there are plenty of components and that this circuit is not recommended for electronics beginners but nevertheless I started the circuit builds by applying heat SN plaster to the four igbts press them onto the heat sinks and secured them in place with an M4 bolts and nut afterwards I marked a suitable position for them on the perf board and enlarged the pin holes to a diameter of 1.5 mm and the heat sing holds to a diameter of 2.5 mm once I was certain that all igbts fit on the perf board I removed them again and labeled each pin according to the pin out out of the igbt I did this because it saved me a bit of confusion while I continued by soldering the rest of the complimentary power electronic components in place once that was done I moved over to the other half of the pro board to create the control circuit I started off with the voltage regulator and the capacitors and continued with the IC sockets the Arduino Nano sockets which consisted of female headers the 555 time rod oscillator the Schmid trigger and finally the two mosfet drivers for the most part I tried to use silver carer wire for the connections but eventually had to utilize a bit of stiff hookup wire after around 5 hours the circuit was complete and it was time to connect the control circuit to a 15v power source once I was sure that all the voltages at the IC sockets were correct I inserted the ic's push the igbts with heat sing in their rightful place and connected them to the Circuit for first test I hooked up the Power Electronics to 15 volt power source as well and measured the voltage at the flyback diodes which presented us with a targeted Square wave and by attaching a proper loads to the inverter the voltage spikes also decrease significantly which means that the circuit works fine so I removed the wires of the primary coil from the olden inverter sold a 210 AWG wires to the new inverter and sold the primary wires to them as a power source I used a lap bench power supply with a maximum output voltage of 30 volts and a maximum current output of 20 amps after connecting its output to the input of the inverter and adding a piece of silver copper wire to the topload it was time for proper test add an input voltage of 8 volts and a frequency of around 60 khz the primary du around 4.5 amps and thus created pretty decent arcs and lighted up CCF lamps without a problem but what was noticeable while playing around with the Tesla coil was that the temperature of the igbts rose up to 50° C and Beyond even though we only used 8 volts on the inputs to fix that you usually utilize an interruptor which is in my case the Arduino it's D5 pin directly connects to the SD or shutdown pin of the mosfet drivers and turns them off completely if D5 is high or turns the drivers on if the five is low so by attaching two potentiometers to the a z and A5 pin of the Arduino and writing a bit of code that utiliz the time zero registers we can output a pwm signal whose frequency and duty cycle is controllable through the potentiometers and lies between 30 HZ and 1 khz and obviously between 0% and 100% duty cycle this way we can still create the same ax as before but it only requires half the power or even less the only problem was that the pwm signal got pretty unstable while the input voltage of the Tesla coil rised but by increasing the distance between the Tesla coil and the potentiometer this problem decreased and was fairly noticeable after I replace the potentiometers with trimmers the last challenge we have to face is that while creating arcs the resonance frequency of the secondary changes a bit which is not only visible on the oscilloscope but also debases the energy transfer that is why I originally planned to include a feedback Transformer on the secondary which supplies the resonance frequency to the mfet drivers I even had jumpers to switch between the 55 timer and the feedback signal and the Transformer actually delivered a suitable signal that we could have worked with but the oscillation without the 55 timer did not want it to start on its own so I will have to fix this problem for the final chapter of this project all we can do for now is setting the duty cycle to 75% cranking up the input voltage to 30 volts and have fun with a so far untuned solid state Tesla Kars which are already pretty scary anyway I hope you enjoyed this project so far if so don't forget to like share and subscribe stay creative and I will see you next time