Fire Alarm System

Fire safety is a critical concern in both residential and commercial settings. Our university EAT group 26 project aimed to address this issue by designing and building an affordable, reliable, and easy-to-use fire alarm system. Using basic electronic components like heat, gas, and flame sensors, we created a system capable of detecting potential fire hazards at different stages and alerting occupants through distinct sound and light signals. The system also includes advanced features like emergency lighting, automatic power disconnection, and water or CO₂ spraying mechanisms, ensuring timely response to fire emergencies.

Sensors

1. Flame Sensor (e.g., 6 black IR LEDs in parallel)
2. Gas Sensor (e.g., MQ135)
3. Thermal Sensor (10kΩ NTC thermistor)

Control and Signal Processing

1. 555 Timer IC (for alarm system)
2. LM358,LM386 Op-Amp IC (as comparators and amplifiers)
3. Relay switches
4. Resistors, Capacitors, and Diodes (values are at diagrams)

Indicators

1. Red, Yellow, and Blue LEDs

Buzzers

1. Piezo-electric buzzer (for sound alerts with multiple tones)

Power Supply

1. 12V DC adapter
2. 3.7V 18650 Li-ion battery
3. 1s BMS circuit
4. 1A boost converter

Connectors and Wiring

1. Screw terminals
2. DC jack connectors
3. Wires and cables

Mechanical and Packaging

1. Project Boxes (Enclosures)
2. For the main control unit and sensor modules
3. Cardboard for Packaging
4. Durable and eco-friendly cardboard for the product box
5. Labels and Stickers
6. For enclosure labeling and user instructions

Tools Required

For Electronics Assembly

1. Soldering Iron and Solder Wire
2. Multimeter (for testing circuits)
3. Wire Stripper and Cutter
4. Drill and Drill Bits (0.7mm, 0.9mm for PCB holes)

For PCB Fabrication

1. Laser Printer (for circuit printouts)
2. Sticker Paper (for PCB designs)
3. Electric Iron (for transferring designs to copper boards)
4. Ferric Chloride (for PCB etching)

For Enclosure and Packaging

1. Precision Cutting Tools (for enclosure modifications)
2. Glue Gun or Glue Sticks (for attaching PCBs to enclosures)
3. Measuring Tape and Ruler (for accurate box design)
4. Graphic Design Software (to create packaging labels and user manuals)

To create a robust alarm mechanism, we used the 555 timer IC configured in different modes for generating distinct alert tones. LM358 operational amplifiers were utilized as comparators and amplifiers, playing a critical role in processing sensor signals and triggering appropriate alarms. The circuit designs were simulated using KiCad, which helped us test and verify functionality before moving to the hardware stage. After finalizing the design, we built a prototype on breadboards to ensure the reliability of the system under real-world conditions.We selected sensors based on availability, cost-effectiveness, and their suitability for detecting fire hazards:

1. Flame Sensor: Built using six IR LEDs in parallel for enhanced sensitivity.
2. Gas Sensor: MQ135, capable of detecting flammable and toxic gases like carbon monoxide and methane.
3. Heat Sensor: A 10k NTC thermistor to monitor temperature changes and trigger alarms at predefined thresholds.

Once the circuit was tested and validated, we designed the PCB layouts using EasyEDA. The PCBs were manufactured in-house using the laser print transfer method. We printed the designs on sticker paper, transferred them to copper boards using an electric iron, and etched the boards with Ferric Chloride. After etching, the boards were drilled using 0.7mm and 0.9mm drill bits to accommodate component leads.

The components were then soldered onto the PCBs, ensuring secure and precise connections. The completed boards were mounted inside project enclosures, with holes drilled for indicator LEDs, connectors, and switches. This step ensured a professional finish while keeping the design compact and user-friendly.

Enclosure Preparation:

1. Selected compact and durable project boxes to house the system.
2. Drilled necessary holes for switches, LEDs, and DC jacks.

Component Placement:

1. Mounted the PCBs inside the enclosures using glue sticks for secure placement.
2. Arranged wiring neatly to avoid clutter and interference.

Indicator Labels:

1. Designed stickers to label holes for LEDs, connectors, and switches.
2. Stickers included labels like "Power," "Alert Levels," "Sensor Inputs," and "Relay Output" to guide users during installation and troubleshooting.

Final Assembly:

1. Secured the enclosures with screws and ensured all external interfaces were accessible.
2. Conducted a final test to verify the system’s performance after assembly.

Ensuring the system works as intended was a critical part of our project. We implemented a thorough testing process to validate each component and the overall functionality of the fire alarm system under simulated and controlled conditions. Here are the methods we used:

1. Heat Sensor (NTC Thermistor): Heated the thermistor gradually using a controlled heat source (e.g., a soldering iron at a distance) to verify that it triggered the alarm at predefined temperature thresholds.
2. Gas Sensor (MQ135): Exposed the sensor to controlled amounts of smoke to confirm it detected gases and activated the system appropriately.
3. Flame Sensor (IR LEDs): Simulated a flame using a lighter or candle at varying distances to ensure accurate detection of IR radiation.

We created a detailed user manual to ensure ease of use for our fire alarm system. It includes clear instructions on installation, operation, and maintenance, along with safety precautions and troubleshooting tips. The manual also features diagrams and visuals to guide users effectively.

Our fire alarm system is packaged in a custom-designed cardboard box that securely holds all components. The package is user-friendly and features clear labeling for easy setup. It also includes our branding and product details.

The development of our fire alarm system presented various challenges, ranging from design complexities to assembly and testing issues. Here’s an overview of the problems we encountered and how we resolved them:

1. PCB Design Challenges

1. Problem: As beginners in PCB design, we struggled with selecting the correct pad and hole sizes for components, leading to alignment issues during assembly.
2. Solution: We referred to standard PCB design guidelines and datasheets for component footprints. After initial mistakes, we created test prints on paper to check component alignment before transferring the designs to copper boards.

2. Lack of Experience in Professional PCB Design

1. Problem: Designing a professional-quality PCB was new to us, and we faced difficulties ensuring proper trace routing and avoiding short circuits.
2. Solution: We used the Design Rule Check (DRC) feature in EasyEDA to identify and fix errors. We also sought feedback from experienced peers and online forums to refine our designs.

3. Finding Compatible Enclosures

1. Problem: Sourcing enclosures that fit our system’s components and allowed for accessible interfaces was challenging.
2. Solution: We visited multiple electronics stores to find suitable project boxes and modified them by drilling additional holes and creating custom slots for connectors, LEDs, and switches.

4. Errors in Prototyping

1. Problem: Errors during the prototyping phase, such as incorrect wiring and component misplacement, caused malfunctions in the circuit.
2. Solution: We meticulously cross-checked the wiring with the circuit diagram and used a multimeter to identify and fix issues. Keeping detailed notes during testing helped us trace and resolve problems quickly.

5. Testing and Calibration Issues

1. Problem: During testing, sensors occasionally gave false positives or failed to respond at expected thresholds.
2. Solution: We adjusted the sensitivity of the sensors by fine-tuning resistor values and tested them under controlled conditions to ensure accurate detection.