Project

# Title Team Members TA Documents Sponsor
73 Occupancy Counter
Aryan Mathur
Ashwin Provine
Tanmay Kant
Jialiang Zhang design_document1.pdf
final_paper1.docx
presentation1.pptx
proposal1.pdf
Team Members: Tanmay Kant (tkant2) Ashwin Provine (provine4) Aryan Mathur (aryanm6)

PROBLEM

In large building environments, managing energy consumption efficiently, particularly for heating, ventilation, and air conditioning (HVAC) systems, presents a significant challenge. HVAC systems often operate on a fixed schedule, with little regard for the actual occupancy of a space, leading to unnecessary energy use and increased operational costs. This inefficiency is especially pronounced in spaces like offices or small meeting rooms due to constant movement. The motivation for the occupancy counter project is to enable more intelligent and adaptive HVAC control by accurately tracking the number of people in a given space. Our experience in the ECE391 Lab (ECEB3026) was a perfect example of HVAC not recognizing the amount of students working late in the lab, with temperature fluctuating constantly. By aligning HVAC operations with real-time occupancy levels, this technology aims to significantly reduce energy consumption and operational costs for large buildings. Achieving precise occupancy counts allows for the HVAC system to adapt its output to the current need, ensuring that energy is not wasted heating, cooling, or ventilating spaces that are not in use or are only partially occupied. Additionally, this system supports a more sustainable approach to building management by reducing the carbon footprint associated with unnecessary energy use.

SOLUTION

Our project is an occupancy counter for rooms. It will utilize [a] Time of Flight Sensor Module(s) for the recognition of room occupants, where we will either use one module, splitting between two zones, or use two modules in order to determine whether the target is entering or exiting the room. The brains behind the sensor will be a WiFi-enabled Arduino Board that will decide the direction of the person’s transit, keeping track of how many people are present in the room. It will update a web interface that can be connected to by any user. The whole device will be powered by USB power brick(s).

SOLUTION COMPONENTS

Control Unit “The ESP8266 is a high-performance wireless SOC that offers maximum utility at the lowest cost and unlimited possibilities for embedding WiFi functionality into other systems.” This module will be the brain and mouth of our project, where data received will be broken down into a few key components, calculated, and sent out as a summary. The data will be analyzed to decide whether the target is moving from Zone 1 to Zone 2 or conversely. From there, the brain will add or subtract to the room count. Once this is complete, the data will be beamed via WiFi to a digital display (monitor, tablet, phone).

Sensor(s) “The VL53L1X is a state-of-the-art, Time-of-Flight (ToF), laser-ranging sensor, enhancing the ST FlightSense™ product family. It is the fastest miniature ToF sensor on the market with accurate ranging up to 4 m and fast ranging frequency up to 50 Hz.” This module acts as the eyes for our project, where the timing of a person crossing the tracked region will be acted upon using a state machine to see the current status.

For example: Entrance ----- Zone 1 ----- Zone 2 ----- Room Stat. A Stat. B Stat. C Stat. D When a person enters, their status will change from A, B, C, to D finally. Should they be exiting, their status will change from D, C, B, to A finally. If a person reaches a status of B or C, but does not continue their transit entering or exiting, respectively, we will not update the counter of the room since the occupancy has not changed.

Power This is the simplest part of the build, where we will use a USB-enabled power brick to provide power to the modules and connect it through a slim and long USB cable. The power for the VL53L1X will be between 2.8V to 5.5V, with the voltage properly regulated by the sensor carrier board while the power for the ESP8266 will be a standard 3.3V input, both powered by DC current.

CRITERION FOR SUCCESS

Exactness/error of count: the count must be exact for up to six occupants, and correct within plus/minus of one person for up to twelve. Since this project is being used as a dependency for a much bigger system, precision and accuracy are important. The actual display should update between two to ten times per minute. This is to ensure that our count is considered live and makes an impact on the energy-saving and HVAC procedures that will ensue. Output data will be transferred via a wireless (WiFi) connection to a display. The sensor we are using has a built-in web interface that can be enabled during setup which will allow for universal access for users of the project.

ATTITUDE DETERMINATION AND CONTROL MODULE FOR UIUC NANOSATELLITES

Shamith Achanta, Rick Eason, Srikar Nalamalapu

Featured Project

Team Members:

- Rick Eason (reason2)

- Srikar Nalamalapu (svn3)

- Shamith Achanta (shamith2)

# Problem

The Aerospace Engineering department's Laboratory for Advanced Space Systems at Illinois (LASSI) develops nanosatellites for the University of Illinois. Their next-generation satellite architecture is currently in development, however the core bus does not contain an Attitude Determination and Control (ADCS) system.

In order for an ADCS system to be useful to LASSI, the system must be compliant with their modular spacecraft bus architecture.

# Solution

Design, build, and test an IlliniSat-0 spec compliant ADCS module. This requires being able to:

- Sense and process the Earth's weak magnetic field as it passes through the module.

- Sense and process the spacecraft body's <30 dps rotation rate.

- Execute control algorithms to command magnetorquer coil current drivers.

- Drive current through magnetorquer coils.

As well as being compliant to LASSI specification for:

- Mechanical design.

- Electrical power interfaces.

- Serial data interfaces.

- Material properties.

- Serial communications protocol.

# Solution Components

## Sensing

Using the Rohm BM1422AGMV 3-axis magnetometer we can accurately sense 0.042 microTesla per LSB, which gives very good overhead for sensing Earth's field. Furthermore, this sensor is designed for use in wearable electronics as a compass, so it also contains programable low-pass filters. This will reduce MCU processing load.

Using the Bosch BMI270 3-axis gyroscope we can accurately sense rotation rate at between ~16 and ~260 LSB per dps, which gives very good overhead to sense low-rate rotation of the spacecraft body. This sensor also contains a programable low-pass filter, which will help reduce MCU processing load.

Both sensors will communicate over I2C to the MCU.

## Serial Communications

The LASSI spec for this module requires the inclusion of the following serial communications processes:

- CAN-FD

- RS422

- Differential I2C

The CAN-FD interface is provided from the STM-32 MCU through a SN65HVD234-Q1 transceiver. It supports all CAN speeds and is used on all other devices on the CAN bus, providing increased reliability.

The RS422 interface is provided through GPIO from the STM-32 MCU and uses the TI THVD1451 transceiver. RS422 is a twisted-pair differential serial interface that provides high noise rejection and high data rates.

The Differential I2C is provided by a specialized transceiver from NXP, which allows I2C to be used reliably in high-noise and board-to-board situations. The device is the PCA9615.

I2C between the sensors and the MCU is provided by the GPIO on the MCU and does not require a transceiver.

## MCU

The MCU will be an STM32L552, exact variant and package is TBD due to parts availability. This MCU provides significant processing power, good GPIO, and excellent build and development tools. Firmware will be written in either C or Rust, depending on some initial testing.

We have access to debugging and flashing tools that are compatible with this MCU.

## Magnetics Coils and Constant Current Drivers

We are going to wind our own copper wire around coil mandrels to produce magnetorquers that are useful geometries for the device. A 3d printed mandrel will be designed and produced for each of the three coils. We do not believe this to be a significant risk of project failure because the geometries involved are extremely simple and the coil does not need to be extremely precise. Mounting of the coils to the board will be handled by 3d printed clips that we will design. The coils will be soldered into the board through plated through-holes.

Driving the inductors will be the MAX8560 500mA buck converter. This converter allows the MCU to toggle the activity of the individual coils separately through GPIO pins, as well as good soft-start characteristics for the large current draw of the coils.

## Board Design

This project requires significant work in the board layout phase. A 4-layer PCB is anticipated and due to LASSI compliance requirements the board outline, mounting hole placement, part keep-out zones, and a large stack-through connector (Samtec ERM/F-8) are already defined.

Unless constrained by part availability or required for other reasons, all parts will be SMD and will be selected for minimum footprint area.

# Criterion For Success

Success for our project will be broken into several parts:

- Electronics

- Firmware

- Compatibility

Compatibility success is the easiest to test. The device must be compatible with LASSI specifications for IlliniSat-0 modules. This is verifiable through mechanical measurement, board design review, and integration with other test articles.

Firmware success will be determined by meeting the following criteria:

- The capability to initialize, configure, and read accurate data from the IMU sensors. This is a test of I2C interfacing and will be tested using external test equipment in the LASSI lab. (We have approval to use and access to this equipment)

- The capability to control the output states of the magnetorquer coils. This is a test of GPIO interfacing in firmware.

- The capability to move through different control modes, including: IDLE, FAULT, DETUMBLE, SLEW, and TEST. This will be validated through debugger interfacing, as there is no visual indication system on this device to reduce power waste.

- The capability to self-test and to identify faults. This will be validated through debugger interfacing, as there is no visual indication system on this device to reduce power waste.

- The capability to communicate to other modules on the bus over CAN or RS422 using LASSI-compatible serial protocols. This will be validated through the use of external test equipment designed for IlliniSat-0 module testing.

**Note:** the development of the actual detumble and pointing algorithms that will be used in orbital flight fall outside the reasonable scope of electrical engineering as a field. We are explicitly designing this system such that an aerospace engineering team can develop control algorithms and drop them into our firmware stack for use.

Electronics success will be determined through the successful operation of the other criteria, if the board layout is faulty or a part was poorly selected, the system will not work as intended and will fail other tests. Electronics success will also be validated by measuring the current consumption of the device when operating. The device is required not to exceed 2 amps of total current draw from its dedicated power rail at 3.3 volts. This can be verified by observing the benchtop power supply used to run the device in the lab.