Compact Anti-Theft Alarm for Bikes (Easy DIY Circuit)

Step 1: PCB Design & Assembly

I designed the circuit PCB using EasyEDA and ordered the final board from PCBWay for a professional finish.

👉 pcbway.com/?from=Promaker1

After receiving the PCB, I placed and soldered the IRLB4132 MOSFET and the PC817 optocoupler in their respective positions as shown in the attached circuit diagram/photo.

This ensures a compact, reliable, and durable build compared to breadboard wiring.

Step 2: Adding Switch, Buzzer, Hall Sensor & Vibration Sensor

Next, I connected the ON/OFF switch, buzzer, Hall-effect sensor, and vibration switch to the PCB:

• ON/OFF Switch: Controls power to the circuit.
• Buzzer: Connect to the MOSFET output so it sounds when the vibration switch is triggered.
• Vibration Switch: Detects any shake or tampering of the bike and triggers the alarm.
• Hall-effect Sensor: Acts as a secure reset — the alarm can only be turned off by placing a magnet near the sensor.

All components are carefully soldered to the PCB, keeping wires short for a compact, tidy setup.

📷 (Insert photo showing all components fixed to PCB and wiring)

Step 3: Trimming, Soldering & Cleaning

After placing all components on the PCB:

• Trim excess legs of all components with side cutters.
• Solder all connections properly, ensuring no cold joints.
• Clean the PCB using liquid flux cleaner or isopropyl alcohol to remove solder residue and flux for a neat finish.

Step 4: Installing the Battery

• I used a small 3.7V Li-ion battery
• Fixed the battery in place using a small amount of gum or double-sided tape to secure it.
• Soldered the +ve and -ve terminals to the PCB carefully, ensuring correct polarity.

Step 5: Making the Enclosure

• Measure the length and width of your PCB carefully.
• Cut a 3mm acrylic sheet to size — I used a laser cutter for precise edges.
• Assemble the acrylic pieces into a box shape to house the PCB and components.
• Use gum or strong adhesive to fix the sides together securely.

This creates a compact and protective enclosure for your bike alarm.

Step 6: Join the First-Ever PCBWay 3D Printing Design Contest!

Unleash your creativity and bring your 3D ideas to life! PCBWay invites all makers and designers to participate in two exciting categories:

• Eon-Themed Designs: Give PCBWay’s mascot, Eon, a fresh new look with your imagination — new outfits, poses, or expressions!
• Open Creative Designs: Design your own original 3D character, figurine, or collectible — from fantasy creatures to action figures.

Why participate?

• Win up to $500 cash, coupons, and certificates
• Have your design professionally 3D printed
• Get featured on PCBWay’s platform and show your talent to the community

How to enter:

Submit your 3D files (STL, STEP, or similar) through the PCBWay Open Source Community. You can enter one or both categories!

Deadline: November 10, 2025 — Don’t miss your chance to turn imagination into reality!

Click here to enter the contest!

Step 7: Installing the PCB and Adding TP4056 Charging Module

• Insert the PCB into the acrylic box and secure it using gum/adhesive.
• Connect the TP4056 charging module:
• Solder wires to B+ and B- terminals of the module (red = +, black = -).
• At the other end, solder a 2-pin female header for easy connection.
• Insulate all exposed wires and solder joints using heat shrink tubing to prevent shorts.

Step 8: Battery Charging Setup

The TP4056 module is now ready and can be used to charge your 3.7V battery safely.

• Simply connect the female 2-pin header from the TP4056 to the male header on the PCB.
• This allows easy plug-in charging without opening the enclosure.

Step 9: Final Testing

• Turn ON the switch and mount the completed alarm box securely on your bike.
• Test the alarm: shake or tap the bike — the vibration switch triggers the buzzer.
• Reset the alarm: place a magnet near the Hall-effect sensor to turn it off.
• Once everything works perfectly, close the acrylic box to protect the circuit.

Step 10: Working & Demo

The DIY bike alarm is now fully functional:

• The vibration switch detects any shake or tampering.
• The buzzer sounds instantly when the bike is disturbed.
• The Hall-effect sensor ensures the alarm can only be turned off using a magnet, keeping your bike secure.

📹 Watch the full working demo on YouTube:https://youtu.be/uCkH_dk6y90?si=77p7BOPlh4xo_rIQ