Project

# Title Team Members TA Documents Sponsor
72 Single-Phase AC Power Analyzer
 Isaac Herink
Jeffrey Pohlman
Joseph Kim
 Eric Tang design_document1.pdf
other1.pdf
Team Members:
- Isaac Herink (iherink2)
- Jeffrey Pohlman (jpohl3)
- Joseph Kim (joseph51)

# Problem
Basic voltage and current measurements do not provide insight into how power is actually being consumed by an AC load. Relevant quantities such as real power and power factor require time-synchronized measurements of voltage and current, which are typically only available from commercial power analyzers. These commercial analyzers are expensive and unnecessary for small-scale laboratory or educational purposes.

# Solution
Design and build a microcontroller-based, single-phase power quality analyzer that measures voltage and current supplied to a load using isolated sensing circuits. The microcontroller will sample both signals at the same time and compute RMS values, real power, and power factor in real time. Measurement data will be transmitted to a computer over USB for display and analysis.

Example use cases include comparing real power and power factor across common loads (incandescent lamp vs. fan motor vs phone charger), measuring load startup behavior, and identifying inefficient or abnormal load behavior in educational lab experiments. It provides students with hands-on exposure to AC power measurements without needing expensive commercial equipment.

The final system will provide a low-cost, embedded tool for monitoring and analyzing AC power behavior in laboratory and educational environments.

# Solution Components

## Subsystem 1 - Power Path (Outlet -> Analyzer -> Load)

This subsystem will provide a safe way to place the analyzer in line with the load without the analyzer acting as the load. The load current will flow through internal wiring (with optional fuse protection), and the analyzer measures current using a CT. This subsystem ensures the analyzer itself does not significantly affect load current/voltage. It also ensures a simple connecting interface between the outlet, analyzer, and load.

Components:
Inlet/Outlet Wiring
Power Cord (McMaster Carr 71535K42),
Receptacle (McMaster Carr 1333N53),
Fuse (Littelfuse 0217005.MXP),
Fuse holder (Littelfuse 01550900Z).

## Subsystem 2 - Voltage Sensing

Provides an isolated low-voltage representation of the line voltage. The transformer secondary is routed to the PCB for conditioning.

Components:
AC Voltage transformer (120 VAC to 6-12 VAC) HQRP TR038 or equivalent.

## Subsystem 3 - Current Sensing

Provides an isolated current measurement to the load.

Components:
Split-core CT 5A to 5mA (B0G1M449JN) - We may use a CT with a larger secondary current.

Voltage and current sensing are isolated with a VT and CT to prevent direct electrical connection between mains and the MCU.

## Subsystem 4 - Analog Signal Conditioning

Converts VT/CT signals into clean and bounded voltages that the MCU can sample accurately. This subsystem performs:

- Voltage scaling: A resistor divider scales the VT secondary down to a target amplitude that is compatible with the ADC.
- Current to voltage conversion: A burden resistor translates the CT secondary waveform into a proportional voltage waveform (for ADC input).
- Input protection: Series resistors and clamp diodes to limit fault voltages and protect ADC ports.
- Filtering: RC low-pass filters to reduce high-frequency noise and prevent aliasing.

This subsystem ensures that the MCU receives waveforms that accurately represent line current/voltage.

## Subsystem 5 - Board Power

The PCB will be powered from USB 5V (or an external 5V source). A 3.3V regulator supplies the MCU.

Components:
Voltage regulator (Diodes Inc AP2112K-3.3TRG1)

## Subsystem 6 - Bias Voltage Generation

Both the voltage and current waveforms will be shifted (biased) to sit within the ADC input range, since the ADC cannot measure negative voltage. The PCB will supply a reference voltage of roughly 1.65V (Vmid = 1.65V) from the 3.3V rail using a resistor divider and decoupling capacitor. The conditioned waveforms are then centered around Vmid to remain between the 0-3.3V ADC range.

## Subsystem 7 - Embedded Processing (MCU)

A microcontroller will sample voltage and current channels at a fixed sample rate. The firmware will remove DC offsets, apply any needed calibration factors, and compute:
- RMS voltage/current
- Real power from the average of v[t]i[t]
- Apparent power, reactive power, and power factor

Components:
MCU (STMicroelectronics STM32F303CCT6 (LQFP-48)),
SWD programming header (Samtec FTSH-105-01-F-DV-K).

## Subsystem 8 - Communication and Display

This subsystem will present our computed values on a pc using USB serial (via a USB-UART bridge). A PC side program (Python or equivalent) will display Vrms, Irms, P, and PF over time.

Components:
USB-UART bridge (CP2102N),
USB connector (GCT USB4085-GF-A).

## Enclosure

We will design and 3D print an enclosure to contain our different subsystems. The enclosure will be self-contained and require only AC power and a USB connection.

# Criterion For Success

- Voltage and current waveforms are sampled at a fixed rate
- The device measures voltage and current simultaneously
- The device computes RMS voltage/current, real power, reactive power, and power factor
- Measurements are displayed on a PC in real time
- RMS voltage is measured within ±5% of a commercial analyzer for a resistive load
-RMS current is measured within ±10% for at least one load in the 0–5 A range
- Real and reactive power is computed within ±10% of a commercial analyzer for a resistive load
- Power factor is reported within ±0.10 and correctly distinguishes resistive (PF ~ 1) and inductive loads (PF < 1)
- The device is in a self-contained enclosure

Illini Voyager

Cameron Jones, Christopher Xu

Featured Project

# Illini Voyager

Team Members:

- Christopher Xu (cyx3)

- Cameron Jones (ccj4)

# Problem

Weather balloons are commonly used to collect meteorological data, such as temperature, pressure, humidity, and wind velocity at different layers of the atmosphere. These data are key components of today’s best predictive weather models, and we rely on the constant launch of radiosondes to meet this need. Most weather balloons cannot control their altitude and direction of travel, but if they could, we would be able to collect data from specific regions of the atmosphere, avoid commercial airspaces, increase range and duration of flights by optimizing position relative to weather forecasts, and avoid pollution from constant launches. A long endurance balloon platform also uniquely enables the performance of interesting payloads, such as the detection of high energy particles over the Antarctic, in situ measurements of high-altitude weather phenomena in remote locations, and radiation testing of electronic components. Since nearly all weather balloons flown today lack the control capability to make this possible, we are presented with an interesting engineering challenge with a significant payoff.

# Solution

We aim to solve this problem through the use of an automated venting and ballast system, which can modulate the balloon’s buoyancy to achieve a target altitude. Given accurate GPS positioning and modeling of the jetstream, we can fly at certain altitudes to navigate the winds of the upper atmosphere. The venting will be performed by an actuator fixed to the neck of the balloon, and the ballast drops will consist of small, biodegradable BBs, which pose no threat to anything below the balloon. Similar existing solutions, particularly the Stanford Valbal project, have had significant success with their long endurance launches. We are seeking to improve upon their endurance by increasing longevity from a power consumption and recharging standpoint, implementing a more capable altitude control algorithm which minimizes helium and ballast expenditures, and optimizing mechanisms to increase ballast capacity. With altitude control, the balloon has access to winds going in different directions at different layers in the atmosphere, making it possible to roughly adjust its horizontal trajectory and collect data from multiple regions in one flight.

# Solution Components

## Vent Valve and Cut-down (Mechanical)

A servo actuates a valve that allows helium to exit the balloon, decreasing the lift. The valve must allow enough flow when open to slow the initial ascent of the balloon at the cruising altitude, yet create a tight seal when closed. The same servo will also be able to detach or cut down the balloon in case we need to end the flight early. A parachute will deploy under free fall.

## Ballast Dropper (Mechanical)

A small DC motor spins a wheel to drop [biodegradable BBs](https://www.amazon.com/Force-Premium-Biodegradable-Airsoft-Ammo-20/dp/B08SHJ7LWC/). As the total weight of the system decreases, the balloon will gain altitude. This mechanism must drop BBs at a consistent weight and operate for long durations without jamming or have a method of detecting the jams and running an unjamming sequence.

## Power Subsystem (Electrical)

The entire system will be powered by a few lightweight rechargeable batteries (such as 18650). A battery protection system (such as BQ294x) will have an undervoltage and overvoltage cutoff to ensure safe voltages on the cells during charge and discharge.

## Control Subsystem (Electrical)

An STM32 microcontroller will serve as our flight computer and has the responsibility for commanding actuators, collecting data, and managing communications back to our ground console. We’ll likely use an internal watchdog timer to recover from system faults. On the same board, we’ll have GPS, pressure, temperature, and humidity sensors to determine how to actuate the vent valve or ballast.

## Communication Subsystem (Electrical)

The microcontroller will communicate via serial to the satellite modem (Iridium 9603N), sending small packets back to us on the ground with a minimum frequency of once per hour. There will also be a LED beacon visible up to 5 miles at night to meet regulations. We have read through the FAA part 101 regulations and believe our system meets all requirements to enable a safe, legal, and ethical balloon flight.

## Ground Subsystem (Software)

We will maintain a web server which will receive location reports and other data packets from our balloon while it is in flight. This piece of software will also allow us to schedule commands, respond to error conditions, and adjust the control algorithm while in flight.

# Criterion For Success

We aim to launch the balloon a week before the demo date. At the demo, we will present any data collected from the launch, as well as an identical version of the avionics board showing its functionality. A quantitative goal for the balloon is to survive 24 hours in the air, collect data for that whole period, and report it back via the satellite modem.

![Block diagram](https://i.imgur.com/0yazJTu.png)