# Title Team Members TA Documents Sponsor
45 Concealed Bike Anti-Theft Device
Alex Wen
Elizabeth Atkinson
Srinidhi Raman
Hojoon Ryu design_document1.pdf
# Team Members

- Elizabeth Atkinson (eatkinso)
- Nidhi Raman (nidhim2)
- Alex Wen (acwen2)

# Problem

College students frequently face the issue of bikes being stolen on campus. Even with a substantial solid steel U-lock, my own bike was stolen this fall, when someone apparently sawed through the u-lock at night. It would be useful to have a device which is difficult to find and remove, but deters potential bike thieves from removing the bike. Additionally, it would be useful to have a system that is relatively universal and can be attached to any bike, rather than being permanently attached to a single bike, since bikes with integrated tracking systems tend to be very expensive.

# Solution Overview

We will make a small, rechargeable, battery-powered device enclosed in a weatherproof enclosure that can easily be attached to most bikes. The device will have a GPS module to receive GPS data, and it will transmit that data over APRS so that the user can easily view their bike's location on any APRS map such as this one:,-88.22279/zoom/13/time/60. Note that this does not require the user to have their own APRS receiver -- The way APRS works is that data transmitted on the APRS frequency is automatically uploaded to the APRS internet system and distributed for everyone to have access to.

In addition to bicycle tracking, the device will also have an alarm system to scare away potential thieves. The owner of the bike will have an RFID tag (this will ideally be in the 860-930 MHz band, so that the user does not need to place the RFID tag very close to the reader for it to be detected) such that while the user is on the bike, the RFID tag can be detected. If the bicycle is moved when the RFID tag is not nearby, it will trigger a loud and annoying alarm to scare away the potential thief.

# Solution Components

## GPS module

We will use a commercially available GPS module to receive GPS coordinates and store them to be transmitted as APRS packets.

## Microcontroller

We will use an STM32 microcontroller to control the operation of the RFID detector, APRS packet radio, GPS module, and alarm system. The microcontroller stores data from the GPS module, packetizes it to be sent over APRS, and will also implement a simple state machine that determines the operation of the device in different circumstances.

## RFID detector

We will use an off-the-shelf RFID tag and an RFID reader module. Ideally, we will use the 860-930 MHz band so that the user does not have to be too close to the reader. To increase ease of use, we will include a visual indicator such as a concealed LED to show whether or not the RFID tag has been detected so that the user doesn't accidentally set off the alarm.

_NOTE_: It is nearly impossible to get RFID readers at the moment, and this will likely get worse when it is time to order parts. We may change this component to another type of "electronic key" for the same effect -- ie, a magnetic bracelet + hall effect sensor so that when the user grabs the handlebars, the bracelet is detected and the alarm is disabled.

## Power

We will power the device with a battery. As a stretch goal, we will include a usb-c charging port, however, there have been significant supply chain issues with battery charging ICs so this may not be possible.

## APRS/LoRa

We will use an RF transceiver IC controlled by the microcontroller to transmit APRS packets. APRS is transmitted over 144.390 MHz at 1.2 kbps with AFSK modulation, so we will need to choose a transceiver IC that satisfies these criteria. We will additionally need to choose an adequate antenna. For our purposes, a small "rubber duck" antenna is likely adequate, but we will investigate this further.

Alternatively -- based on part availability and apparent difficulty -- we will implement this feature using LoRa. LoRa has the advantage of not needing a radio license to operate, but it does require an external receiver unlike the APRS internet gateways that already exist in many places.

## Alarm

We will use a loud buzzer or other alarm to scare away the thief.

## Physical configuration

A key aspect of the system is that it is cleverly concealed and thus difficult for a would-be thief to find and remove. We will take advantage of the fact that bike structures are frequently hollow to secure the device inside of the metal tube structure of the bike. The RF components (GPS receiver and APRS transmitter) obviously cannot be enclosed in the metal structure - instead, we will place the GPS module either on the ends of the handlebars, concealed to look like part of the gearshift, or in the stem so that the antenna of the GPS receiver is covered by a plastic cap on the top of the stem.

To make it difficult for a thief to find the device, we will position the alarm spatially far from the controller, so that the sound of the alarm will not reveal the location of the anti-theft device.

## Note on radio licensing:
APRS is in the amateur band and thus requires a license to operate -- I (Elizabeth) and Nidhi both have licenses, so we can legally test the device under our callsigns. If we were to implement the beaconing feature in LoRa, licensing will not be an issue since LoRa does not require a license.

# Criterion for Success

- The device triggers an alarm if someone who does not have the electronic key (RFID tag) moves it from a stationary location.
- The device provides a visual indicator if the electronic key is detected or not.
- The device receives GPS coordinates.
- The device transmits APRS/LoRa packets with its current location. _Stretch goal_: also include other parameters such as distance traveled that day and average speed.
- The device is concealed within the bike structure.
- The device does not rely on an external power supply. _Stretch goal_: the device is rechargeable.

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