Final Project: Car Side Mirror Theft Alarm System¶
Project Overview¶
This project focuses on developing a car side mirror theft alarm system that detects unauthorized removal or tampering of a vehicle’s side mirror and triggers an alert.
The system uses a Hall effect sensor and magnet pair to monitor the presence of the mirror. When the mirror is detached, the magnetic field is disrupted, and the system activates an alarm.
Project Planning¶
System Concept¶
Working Principle¶
- A magnet is attached to the mirror housing.
- A Hall effect sensor (KY-003) is fixed to the car body.
- When the mirror is in place → magnetic field detected.
- When removed → magnetic field lost → alarm triggered.
This project presents a digitally fabricated anti-theft system designed to protect car side mirrors from unauthorized removal. The system operates by detecting the presence of a magnetic field using a Hall effect sensor. When the mirror is detached, the magnetic field disappears and an alarm is triggered.
The development follows the Fab Academy workflow, combining 3D design, electronics production, CNC milling, and laser cutting into a single integrated system.
What does it do?¶
The system continuously monitors whether the car side mirror is attached or removed. A magnet is fixed to the mirror, while a Hall effect sensor is placed on the car body. As long as the mirror is in position, the magnetic field is detected and the system remains inactive. Once the mirror is removed, the absence of the magnetic field is immediately detected, and the system activates an alarm through a buzzer and LED indicator.
This creates a simple but effective real-time theft detection mechanism.
Who’s done what beforehand?¶
Existing automotive alarm systems typically focus on door access, vibration sensing, or motion detection. However, side mirror theft is a common issue that is not specifically addressed in most low-cost systems.
This project builds on basic magnetic sensing principles used in door sensors but adapts them into a compact and dedicated solution for mirror protection. The emphasis here is on simplicity, accessibility, and full fabrication within a Fab Lab environment.
What I design?¶
The project involved designing both the electronic and mechanical aspects of the system, as well as integrating them into a working prototype.
On the electronics side, a custom circuit was developed to interface the Hall effect sensor with an ESP32 microcontroller, which processes the signal and controls the alarm outputs. The PCB was designed using digital tools and fabricated locally.
On the mechanical side, several custom parts were created, including a sensor holder that attaches to the car body, a magnet housing that fits onto the mirror, and an enclosure that protects the electronics. These parts were designed to ensure proper alignment, durability, and ease of installation.
The final design brings these elements together into a compact and functional system.
What materials and components I used?¶
The electronic system is based on an ESP32 micro controller, which provides sufficient processing capability and flexibility for future expansion. A KY-003 Hall effect sensor is used to detect the magnetic field, while an active buzzer and LED provide audible and visual feedback when an alarm condition is triggered.
Power is supplied using a rechargeable lithium-ion battery, supported by a TP4056 charging module and a step-up converter to ensure stable voltage levels.
Mechanically, PLA filament was used for 3D printing the enclosure and mounting parts. Additional structural elements were produced using laser-cut acrylic or plywood. FR4 material was used for PCB fabrication, and standard fastening methods such as screws, epoxy, and automotive-grade tape were applied to secure the system.
How I made?¶
The project combines multiple digital fabrication techniques.
The mechanical components were first designed in CAD using Fusion 360 and FreeCAD. These designs were then exported for fabrication, with some parts produced through 3D printing and others using laser cutting depending on their function and required precision.
The electronic circuit was designed in KiCad and Fusion 360 Electronics. After finalizing the layout, the PCB was fabricated using an FR4 board and a 3040 CNC milling machine. The milling process involved generating toolpaths, engraving traces, drilling holes, and then soldering the components manually.
Laser cutting was used to create flat structural parts and mounting elements, offering high precision and speed. This combination of additive and subtractive manufacturing allowed for efficient prototyping and iteration.
What processes were used?¶
This project integrates several core Fab Lab processes into a single workflow.
The design phase involved creating both 3D models and electronic schematics using professional CAD and EDA tools. These designs were then translated into fabrication files suitable for CNC milling, laser cutting, and 3D printing.
The PCB fabrication process used FR4 material and a CNC router to produce the circuit board. In parallel, mechanical parts were fabricated using additive manufacturing (3D printing) and subtractive methods (laser cutting).
Finally, embedded programming was used to define the system behavior, allowing the ESP32 to read sensor data and control the outputs accordingly.
What worked? What didn’t?¶
The core detection mechanism proved to be reliable once the correct alignment between the sensor and magnet was achieved. The system responds quickly to mirror removal and consistently triggers the alarm without delay.
However, several challenges were encountered during development. Initial tests showed false triggering due to weak magnetic fields and improper positioning. This was resolved by selecting a stronger neodymium magnet and refining the mounting design.
Another issue arose during PCB fabrication, where incorrect milling depth affected trace quality. Adjusting the CNC calibration solved this problem. Power stability was also improved by adding proper regulation and filtering.
On progress¶
…