Overview
In my PHYS 420 project, I am building a Solid State Tesla Coil (SSTC) to explore its ability to convert electrical frequencies into audible sound. The SSTC is a Tesla Coil which is governed by transistors that convert low DC voltage into AC, which is then stepped up to an incredibly high voltage to be stored in a Toroid . This high-voltage area ionizes air molecules, leading to the discharge of electrons. Notably, the frequency of this discharge can be controlled using a NE555 timer.Equipment Needed
Below is a list of Equipment that is used to build this tesla coil, certain parts will have there part number next to it which can be easily bought through companies like DIGIKEY:Circuit for Tesla Coil
Interpretation of Circuit
This circuit was designed by LabCoatz designs. The cirucit takes in an AC voltage which gets turned into DC voltage using rectifiers (diodes put in opposition of each other). The DC voltage then flows through the circuit. A gate driver circuit, controlled by a NE555 timer, regulates the path of the DC voltage by turning on and off two Insulated-Gate Bipolar Transistors (IGBTs) at a frequency set by the NE555 timer's potentiometer. An antenna plays a crucial role by picking up the resonant frequency of the Tesla Coil. This resonance depends on various factors, including the number of windings in the transformers, their lengths, and the overall spatial dimensions of the coil with respect to there surrounding environment. The rapid switching of the IGBTs effectively converts the DC voltage into a high-frequency AC voltage. When this AC voltage passes through the primary coil, it generates a changing magnetic field due to the alternating current direction. According to Lenz's Law, this changing magnetic field induces a current in the nearby, highly-wound secondary coil. This process steps up the voltage to a very high level. The high voltage causes current to flow into the topload capacitor, where it is stored until the electric field strength reaches approximately 3 MV/m (3 x 10^6 V/m). At this point, a rapid discharge occurs.How to build the Transformer ( Primary and Secondary Coils)
For the main transformer, I used JAVATC to figure out the number of windings needed for my primary and secondary coils. The website can output various specifications of a tesla coil such as its resonant frequency. For this cirucit, it is best to aim for a resonant frequency of 100KHz-300KHz. Below is the specifications I used;Initial Specifications:
Primary coil:
8-10 turns
16 AWG enameled wire
10’’ diameter loops
height of 2’’
Secondary coil:
1700 turns
30AWG enameled wire
3.5’’ diameter loops
height of 17’’
How to build the Topload
To build the Topload, a Toroid can be a great way of storing the energy for it to discharge and give it the 'Tesla Coil Aesthetics". It is essentially a smooth, spherical metal object placed atop the secondary coil. While some designs incorporate wires, simple and effective top loads can be made using metal bowls. An economical option is to create a donut shape from an aluminum air duct. To achieve a smoother outer surface, which optimizes discharge performance, you can coat it with aluminum or copper tape. Here's the key takeaway: a smoother topload surface translates to larger discharge spikes. Discharges tend to concentrate on pointed areas, so wrinkles or imperfections can lead to unseen energy loss. Solid-state Tesla Coils operate at high frequencies. To maximize discharge performance, consider attaching a discharge rod to the topload. This rod, ideally made of any metal with a very sharp point, significantly concentrates the charge buildup, resulting in impressive discharge bolts. Important Safety Note: Building and operating a Tesla Coil involves high voltages and currents. Always prioritize safety by following established guidelines and wearing proper personal protective equipment (PPE) when working on the project.Some Tips and Tricks
Safety Precautions:Circuit Design and Construction:
Safety Measures:
Component Selection and Replacement:
Testing and Troubleshooting:
Heat Management:
Operation and Maintenance:
Material Selection:
Fuse Integration:
Troubleshooting Tips:
Basic Process of How Tesla Coil Works
Inspiration for this Tesla Coil project came from a design by LabCoatz, a YouTube channel known for its engaging content that explores exciting physics applications. In a Tesla Coil, alternating current (AC) flows through a primary coil with a relatively low number of windings. The changing direction of current creates a changing magnetic field that induces a current in a nearby secondary coil with many more turns. This process steps up the voltage to a high level. The high-voltage output is then stored in a topload capacitor located at the top of the Tesla Coil. When the electric field strength within the topload surpasses 3 MV/m (3 x 10^6 V/m), it discharges rapidly. The audible sound produced during discharge results from the rapid vibration of air molecules at the frequency of the changing magnetic field.
Physics Background
To understand how this Tesla Coil works, I have broken down the basic physics !Electromagnetism:
Electromagnetism, a cornerstone of modern physics, dictates how electrically charged particles interact. Pioneered by Scottish physicist James Clerk Maxwell, this fundamental force manifests through two interwoven fields: the electric field, exerting pushing or pulling forces on charged objects, and the magnetic field, generated by moving electric charges and affecting nearby wires or magnets with magnetic properties. The key lies in their dynamic relationship. A changing electric field, like those produced within the Tesla Coil, creates a swirling magnetic field, as predicted by Maxwell's equations. Conversely, a changing magnetic field can induce movement in nearby electrons. In essence, electromagnetism reveals an elegant unification: moving electric charges create magnetic fields, and changing magnetic fields can influence electric fields. This intricate interplay is harnessed by the Tesla Coil, leading to the cool electrical phenomena you'll create.
Discharing Charges:
The Tesla Coil's signature phenomenon, formally known as corona discharge, arises from the ionization of the surrounding air molecules. This ionization occurs when the electric field strength at the Tesla Coil's breakout point, typically the topload, surpasses a critical threshold. At standard atmospheric pressure (around 101 kPa, equivalent to sea level), air molecules become ionized when exposed to an electric field exceeding roughly 30 kV/cm. This powerful electric field is a consequence of the high voltage generated by the Tesla Coil's transformers. In simpler terms, the intense electric field creates a situation where air molecules lose electrons, becoming electrically charged themselves, and the visible glow we observe is a result of this phenomenon.
Transformers:
Tesla Coils rely on transformers to crank up the voltage. 'These clever devices use electromagnetism to create a voltage boost. Imagine a changing magnetic field (caused by the alternating current in the transformer) inducing an electrical push (EMF) in a nearby coil. The number of turns in each coil acts like a gear ratio. More turns in the secondary coil, compared to the first (primary) coil, translates to a higher voltage output. Essentially, the transformer acts like a voltage booster, using electromagnetism to create the high voltage needed for the Tesla Coil's impressive electrical effects.
Lenz's Law:
Another key player in the Tesla Coil's magic is Lenz's Law. This law dictates how a changing magnetic field induces an electric current, but with a twist: the induced current always tries to oppose the change that caused it. In the Tesla Coil, the primary coil's changing magnetic field (due to AC current) induces a current in the secondary coil. However, Lenz's Law ensures this current flows in a direction that counteracts the initial magnetic field change. This seemingly counterintuitive effect is crucial. It's this opposition that ultimately leads to the high-voltage output in the secondary coil, a vital step in transforming low-voltage input into the powerful electrical discharges that define the Tesla Coil's operation.
Design Plans
My Solid State Tesla Coil project was primarly designed with the assitance of various engineers in the PHAS community and the help of the CAD software OnShape.
The figure above shows the final product of how I designed my Tesla Coil. I implemented various additional parts such as a opened sided box to hold my the circuit box and keep the power source away from the toplaod of the tesla coil. Aswell I included handles on the side to make easily movable. My final project involved various tools including;
For the primary coil holders, I 3D printed a design created on the CAD software as shown on the figure above. This was attached to the wooden slabs I cut out using a water jet as well as some power tools.
One of the hardest aspects was winding the secondary coils. I used a Lathe which held my 21" PVC pipe. I only winded up to a length of 17", leaving a couple inches for error and the connection caps. The winding involved setting the Lathe a pretty slow rotational speed, and allowing the thin wire to move at a slow speed to cover as much of the PVC as possible. In additon, keeping the wire tight was critical. After around 2 hours, I had a nicely winded solenoid of about 800 turns to use as my Secondary Coil for the Tesla Coil.
For my toroid component, I assembled it using an aluminum air duct with some aluminum tape. To keep the shape circular, I attached some metal sheets of diameter 10" and had everything connected using the aluminum tape. One side effect with using a lot of tape was I noticed when the Tesla Coil was on, the smell of burning glue became apparent due to the heating from the toroid.
Building the circuit was one of the most enjoyable aspects. I used a soldering iron and solder to assemble this circuit. Testing this circuit was critical in ensuring the Tesla Coil was safe to opperate. I used various screw terminals and IC holders in case I needed to easily change components.
Before turning on the circuit, I had to ensure various tests were done to check that the circuit was doing what it was supposed to. Conducting tests on all the IC's is a good starting point, then moving along to making sure all the output pins have the right voltage, having a multimeter can be helpful. Checking the IGBT's is the next step. In the Oscilloscope photo above, you can see a blue and orange opposing signal, which is what you want to see. It shows how the voltage is changing direction rapidly, which is what the IGBT's purpose are in this circuit. Aswell as you can see an on and off time, which is set by the NE555 timer. In the video above, you can see moving the potentiometers dial can change the duty cycle of the NE555 timer. I even tested the secondary and primary coils before sending in the high current from the circuit board. This was done by using a frequency generator and monitoring the amplitude change on the oscilloscope that was connected to the secondary. You could observe the resonance behaviour when setting the frequency generator at the resonance frequency of the Tesla Coil by doing this method!
For the outside box, I used a waterjet to cut out a design I created in the CAD software. In addition, I engraved my name and a logo on the side for a finishing touch using a laser cutter in our lab room. This was to make the final product look fancier as well take the opportunity to use various tools in our lab room.
For the circuit box, I used metal material in case a loose wire needed to be grounded since I connected the metal box to the power sources ground. I used some power tools to cut out various holes since various wires and knobs needed to leave the box. Organization was crucial for this part since it could be quite dangerous if everything was too packed and not thought out properly.
The final result of this project was quite satisfying. After months of hard work, everything fit together neatly. Below Ive also put some videos of the tesla coil on ‘low power’ vs ‘high power’ setting.
A cool addition to the Tesla Coil project, which im currently in the process of is turning it into a music device. If you interrupt the Gate Driver with an alternating frequency (a music signal ) rather than using the NE555 timer, the discharge electrons will vibrate the air molecules at that frequency, which will in turn make the “buzzing sound” from the discharge into a song!