This project is a high-visibility, pure-hardware bicycle rear safety light assembly. Unlike modern designs that rely on fragile microcontrollers or firmware that can glitch, this module uses discrete hardware logic gates and analog switching to deliver instant, fail-proof brake and turn signaling.

It interfaces directly with handlebar switches and brake levers via a standard 5-pin connector, providing automotive-grade road safety for any bicycle or E-bike setup.

🛠️ Key Features & Engineering Highlights

Pure Discrete Logic Control: The entire switching brain consists of robust, ultra-reliable N-channel MOSFETs (2N7000 BK / BS170). Fusing analog switching with digital inputs eliminates the need for programming, boot times, or software bugs.

High-Efficiency Mid-Power LED Array: Features 18 premium XINGLIGHT 2835 SMD LEDs split into two targeted safety clusters:

10x Amber/Yellow LEDs (XL-2835UYC-02FJ) for crisp, high-visibility left and right turn signal animations.

8x Super-Bright Red LEDs (XL-2835SURC-02FJ) clustered to form an intense, instant-on brake indicator.

Advanced Thermal Management: Because mid-power LEDs pull sustained current (60mA per string), the board features heavy-duty 2512 and 2010 surface-mount power resistors. These massive passive footprints easily dissipate up to 1 Watt of heat continuously, preventing thermal runaway and drastically extending the life of the light.

Vibration-Proof Design: The high-stress, external wiring link uses a sturdy 5-Pin JST XH header. Combining surface-mount passives with through-hole connectors ensures the board handles the constant bumps and vibrations of rough road cycling without cracking solder joints.

⚙️ How it Works

The circuit operates as a solid-state switching matrix. The external handlebar controls feed raw signal voltages into the 5-pin JST input connector.

When an input line goes high (e.g., pulling the brake lever or toggling a turn switch), it charges the gate of the corresponding N-channel MOSFET. The MOSFET instantly saturates, pulling the cathode path of the target LED string to ground and completing the high-brightness power circuit. The 10kΩ pull-down resistors keep the lines perfectly quiet when switches are open, preventing any accidental road-noise flickering.

🚀 Build & Manufacturing Notes

This board is fully optimized for PCBWay Turnkey PCB Assembly (PCBA).

All passives and LEDs are surface-mount (SMD) for seamless, fast automated reflow.

Pinout Alert: If you build this exact layout, notice that the transistor footprint is customized linearly for a Drain-Gate-Source (D-G-S) pin configuration. Be sure to source the bulk 2N7000 BK variant from Central Semiconductor to perfectly match the orientation of the board traces without needing to flip standard transistors backwards!