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# Title Team Members TA Documents Sponsor
68 Power-Factor-Corrected Musical Tesla Coil
 Ali Albaghdadi
Kartik Singh Maisnam
 Shengyan Liu design_document1.pdf
final_paper1.pdf
proposal1.pdf
# Gentle Giant: A Power-Factor-Corrected Musical Tesla Coil

Team Members:
- Ali Albaghdadi (aalba9)
- Kartik Maisnam (maisnam2)

# Problem

Tesla coils are impressive visual and auditory devices; some can a surprising range of sounds using arc discharges, and thus have found uses as display pieces in entertainment and STEM education. A particularly large one is permanently mounted to a ceiling inside the Museum of Science and Industry in Chicago. However, for the majority of their existence, they have been crude instruments. The way they are built and operate typically results in a suboptimal use of AC power, also known as a poor power factor, and even with the advent of "solid-state" Tesla coils (SSTCs) that use power semiconductors, the problem has not improved. Areas with lower-voltage mains like the United States are often at a disadvantage due to details in many of these implementations. Further, when scaling up to large Tesla coils for use in performances, they can have a significant effect on the grid. Solving these problems can improve the efficiency and portability of these novelty constructions.

# Solution

We aim to build, for a comparatively low cost, a Dual-Resonance Solid State Tesla Coil (DRSSTC) with an active Power Factor Correction (PFC) front end. The combination of these two advancements puts our Tesla coil at the very forefront of Tesla coil hardware technology, and solves many of the technical issues with other modern designs.

Some background: Tesla coils are effectively giant transformers, with a secondary winding that has many times more turns than the primary. Conventional SSTCs operate by first rectifying mains AC to a high-voltage DC, then using a half-bridge or full-bridge of power semiconductors to switch the primary of the Tesla coil. This results in a very large voltage being generated in the secondary, which causes it to release arc discharges.

A major benefit that DRSSTCs like ours bring over SSTCs is that it operates more like a resonant converter. In the design phase of the transformer, the primary and secondary must be tuned to have close LC resonant frequencies. During operation, feedback from the primary is used to switch it at its resonant frequency, which results in energy being built up in the system more quickly and more impressive arc discharges. This energy buildup must be stopped intermittently by an external PWM signal called an interruptor (which can simultaneously be used to modulate music into the arc discharges). The primary feedback also enables zero-current switching (ZCS), reducing thermal losses in the power stage to near zero.

We choose to improve even further by designing a digitally controlled boost-type active PFC to create the high-voltage DC rail. This brings with it several benefits of its own, like improving system power factor, making the system agnostic to mains voltage and frequency, and allowing for smooth capacitor precharging without the use of a separate precharge circuit.

With a high power factor, both of the following are possible:
1. For the same apparent AC power, the generated arcs can be larger
2. Arcs of the same size can be generated for less apparent AC power

Thus the whole system consists of the PFC, the feedback controller, the power stage, and the transformer.

# Solution Components

## Boost-type PFC Stage

This subsystem draws power from the AC mains and creates a 400-volt DC rail. It is digitally controlled using an STM32F103 microcontroller, which allows it to ramp the voltage for precharging and compensate for different mains voltages and frequencies.

A boost-type PFC consists of a bridge rectifier, an input inductance, an output capacitance, a FET and an individual diode. We plan to use the Panjit KBJB bridge rectifier, Rohm SCT3120ALHR SiC FET and Wolfspeed C6D04065A SiC diode. Since we only need one of each in the product, their costs are negligible. A Texas Instruments UCC5710x gate driver can be used to allow the STM32F103 to drive the FET. The projected frequency of switching is 50kHz.

## Feedback controller

This subsystem implements a simple ZCS feedback controller using comparators and digital logic chips, and utilizes a long plastic optical cable to safely and remotely play simple musical notes via PWM (this is the interruptor signal). The optical receiver will be an Industrial Fiber Optics IF-D95T, which is an inexpensive device that has been highly proven in Tesla coil design history. Though in theory the microcontroller could also perform the logic task, we felt that it would not have low enough latency. The feedback itself is provided by a current transformer made of a Fair-Rite #77 ferrite core, which feeds into a burden resistor. Microchip MCP6561 comparators perform the zero crossing detection, and 74HCT logic chips manipulate the signal, combine it with the interruptor signal, and create gate drive waveforms for the power stage.

## Power stage

The power stage simply consists of a full bridge of four 60N65 IGBTs, and the primary LC is connected in the middle. The switches are driven by gate drive transformers (GDTs) to save cost and complexity versus developing a solution with isolated gate drive ICs. GDTs have been by far the leading solution to drive SSTC power semiconductors, and there is little incentive to do otherwise.

## Transformer

This is the Tesla coil itself. It will stand at around three feet tall once completed. It has no electronic components, but its physical design places some constraints on the electronic components. Preliminary calculations place the resonant frequency of the primary at around 200kHz.

# Criterion For Success

A PWM generator with an optical transmitter needs to be able to remotely start and operate the Tesla coil, causing it to release arc discharges. The arc discharges should be at least 1 foot in length, and the power factor of the whole system needs to be above 0.95 during normal operation.

Modularized Electronic Locker

Jack Davis, Joshua Nolan, Jake Pu

Modularized Electronic Locker

Featured Project

Group Member: Jianhao (Jake) Pu [jpu3], Joshua Nolan [jtnolan2], John (Jack) Davis [johnhd4]

Problem:

Students living off campus without a packaging station are affected by stolen packages all the time. As a result of privacy concerns and inconsistent deployment, public cameras in Champaign and around the world cannot always be relied upon. Therefore, it can be very difficult for victims to gather evidence for a police report. Most of the time, the value of stolen items is small and they are usually compensated by the sellers (Amazon and Apple are very understanding). However, not all deliveries are insured and many people are suffering from stolen food deliveries during the COVID-19 crisis. We need a low-cost solution that can protect deliveries from all vendors.

Solution Overview:

Our solution is similar to Amazon Hub Apartment Locker and Luxer One. Like these services, our product will securely enclose the package until the owners claim the contents inside. The owner of the contents can claim it using a phone number or a unique user identification code generated and managed by a cloud service.

The first difference we want to make from these competitors is cost. According to an article, the cost of a single locker is from $6000 - $20000. We want to minimize such costs so that we can replace the traditional mailbox. We talked to a Chinese manufacturer and got a hardware quote of $3000. We can squeeze this cost if we just design our own control module on ESP32 microcontrollers.

The second difference we want to make is modularity. We will have a sensor module, a control module, a power module and any number of storage units for hardware. We want to make standardized storage units that can be stacked into any configuration, and these storage units can be connected to a control module through a communication bus. The control module houses the hardware to open or close all of the individual lockers. A household can purchase a single locker and a control module just for one family while apartment buildings can stack them into the lockers we see at Amazon Hub. I think the hardware connection will be a challenge but it will be very effective at lowering the cost once we can massively manufacture these unit lockers.

Solution Components:

Storage Unit

Basic units that provide a locker feature. Each storage unit will have a cheap microcontroller to work as a slave on the communication bus and control its electronic lock (12V 36W). It has four connectors on top, bottom, left, and right sides for stackable configuration.

Control Unit

Should have the same dimension as one of the storage units so that it could be stacked with them. Houses ESP32 microcontroller to run control logics on all storage units and uses the built-in WiFi to upload data to a cloud server. If sensor units are detected, it should activate more security features accordingly.

Power Unit

Power from the wall or from a backup battery power supply and the associated controls to deliver power to the system. Able to sustain high current in a short time (36W for each electronic lock). It should also have protection against overvoltage and overcurrent.

Sensor Modules

Sensors such as cameras, motion sensors, and gyroscopes will parlay any scandalous activities to the control unit and will be able to capture a photo to report to authorities. Sensors will also have modularity for increased security capabilities.

Cloud Support

Runs a database that keeps user identification information and the security images. Pushes notification to end-users.

Criterion for Success:

Deliverers (Fedex, Amazon, Uber Eats, etc.) are able to open the locker using a touchscreen and a use- provided code to place their package inside. Once the package is inside of the locker, a message will be sent to the locker owner that their delivery has arrived. Locker owners are able to open the locker using a touchscreen interface. Owners are also able to change the passcode at any time for security reasons. The locker must be difficult to break into and offer theft protection after multiple incorrect password attempts.

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