Project

# Title Team Members TA Documents Sponsor
21 MULTI-SENSOR MOTION DETECTOR FOR RELIABLE LIGHTING CONTROL
 Joseph Paxhia
Lukas Ping
Sid Boinpally
 Shiyuan Duan proposal1.pdf
Team Members:
- Joseph Paxhia (jpaxhia2)
- Siddarth Boinpally (sb72)
- Lukas Ping (lukasp2)

**PROBLEM:**

In offices, classrooms, and lecture halls worldwide, motion sensors are commonly used to automate lighting control. While convenient, these systems share a critical flaw: lights often switch off when people remain in the room but are relatively still—such as when typing, reading, or watching a presentation. This leads to frustration, disrupts productivity, and creates an inefficient work environment. The root of the issue lies in the reliance on Passive Infrared (PIR) sensors, which detect the infrared radiation emitted by warm bodies. Although effective for detecting large movements, PIR sensors struggle with micromotions, are prone to false triggers, and rely on fixed timeout settings. As a result, they fail to consistently recognize human presence.

**SOLUTION:**

Our approach introduces a multi-stage verification system to improve reliability while preserving the strengths of current technology. PIR sensors remain useful for their fast response to initial entry and larger movements, so we retain them for triggering lights when someone walks into a room. To overcome their limitations, we integrate a millimeter-wave (mmWave) radar sensor, which excels at detecting fine micromotions such as breathing or subtle hand movements.
This introduces the following subsystems:
- Control and Processor
- Sensing System
- Lighting Interface
- Power

**Subsystem #1: Control and Processor**

Primary Responsibilities:

- Take in the sensor data from the PIR and the mmWave sensors.
- Process this data and make a decision to stay on, gradually turn on, dim, and stay off.
- Send this decision out.

The control and processor subsystem will take in the PIR and mmWave sensor data, determine whether the lights should be off, on, gradually illuminate, or dim, and output this decision as a PWM (for the brightness of the lights) from the microprocessor for the lighting system to accurately drive the lights. By combining the two sensors, false positives and negatives will be reduced from the surrounding environment by combining the signals and using logic to combine the data sent in from both sensors. A STM32 microprocessor will be utilized, as it has the capability to process these signals and is best for filtering and dimming.

**Subsystem #2: Sensing System**

Primary responsibilities:

PIR: instant “walk-in” detection, coarse motion, low power standby.

mmWave: micromotion detection (breathing, typing), presence confirmation, and false-trigger suppression.

We will be using the PIR for fast wake and coarse motion and the mmWave for verification/hold and micromotion detection. Using both avoids having PIR false-offs while making sure that we have semi-instant illumination.

Basic state machine / functionality:
1. Idle / Vacant: PIR = low, mmWave = no-presence → lights off, system in low-power monitoring.
2. Wake / Entrance: PIR triggers → gradual illumination, start hold-timer and mmWave high-sensitivity window.
3. Occupied (confirmed): mmWave confirms presence (micro-motion or persistent reflection pattern) OR PIR continues to detect motion → remain ON; reset hold timers on detections.
4. Low-activity (PIR no longer seeing motion): PIR goes quiet → enter mmWave verification window: if mmWave detects micro-motion within verification window, remain in Occupied. If mmWave sees nothing for Nverify seconds → move to Vacant.
5. mmWave & PIR quiet → lights off, enter low-power scans at low duty.

**Subsystem #3: Lighting Interface**

Primary responsibilities:

- Gradually turn lights on and off
- Keeping lights on

Our gradual illumination will employ a 0-10V analog dimmer, which is essentially a subcircuit block. This is a very widely used and accepted lighting control interface that reads a DC voltage to control brightness on an LED. The driver itself still runs on AC Main power.

The subcircuit is comprised of these components:

- Microcontroller - To generate a high frequency PWM (Pulse Width Modulation) proportional to the desired brightness
- Filter - to transform the PWM to a DC voltage
- Op Amp Buffer / Amplifier- Since our STM32 microcontroller outputs up to 3.3 V and we need to generate up to 10 V DC
- Any protection needed - Resistors and diodes used as needed
- Output to LED

This 0-10V analog dimmer also can keep the lights on through the microcontroller generating a constant voltage above ~1.0 V. Once people leave the room and the controller doesn’t detect anyone, the inverse can be done to gradually turn the lights off (10 - 0 V).

Note: We will have to do some math to find a suitable slew rate for the brightening and dimming. We are thinking of having 3 different rates:

1. Gradual brightening - should take around 0.5-1 seconds for the lights to go from off to desired brightness
2. First dimming - takes around 10 seconds when the sensor first detects no people in the room.
3. Final shutoff - takes around ~2 seconds to fade to fully off. This is done after first dimming is completed and the sensor still detects no activity in the room.

**Subsystem #4: Power**

1. Take power from the fixture’s AC mains (120/230 VAC).
2. Use a dedicated isolated SMPS / LED-driver tap or internal LED driver rails to create regulated DC rails for electronics (3.3 V, 5 V, and optionally 1.8 V).
3. Keep the LED power path (the high-power LED driver) electrically separate from the low-voltage sensing electronics; provide good isolation and filtering between them.

The system is powered from AC mains, which feeds the LED driver to provide constant-current illumination and also supports mains sensing and surge protection components such as fuses and MOVs. All low-voltage electronics—including the MCU, mmWave radar module, PIR sensor, and any communications modules (Wi-Fi/BLE)—operate on DC, typically 3.3 V, with some modules optionally requiring 1.8 V or 5 V. The MCU manages these peripherals and interfaces with sensors using logic-level signals, ensuring safe and reliable operation of the sensing and control system.

**Criterion for Success**

The light should gradually turn on when somebody enters a room, and it should start the turn on process without much wait time. While it is on, and people are still present in the room, the light should not start to dim. When the room becomes empty, the light should start to dim (after a sufficient wait time) and turn off. In addition, this should be able to detect motion within 10-15 m. of the sensor.

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)