Analog Bicycle Light Schematic
Worked for 10 sec
The editable layer value is
Bottom for standalone artwork on this stackup, so I’m applying that exact layer now.Worked for 1 min 34 sec
The artwork is now on the valid bottom-side layer. I’m visually checking the result and running DRC.
Worked for 11 sec
The layout checks are clean; I’m explicitly setting the PCB silkscreen color to white so the new bottom artwork renders as intended in 3D.
Worked for 57 sec
Updated only the PCB bottom-side artwork: added the bicycle/light graphic, divider lines, five feature descriptions with line icons, and centered “Flux” branding. Silkscreen color is set to white.
Remaining issues:
- None reported by DRC.
- Schematic, electrical connections, component placement, and routing were unchanged.
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Final manufacturing review
Verify BOM
Export fabrication files
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Simple Analog Smart Bike Light — Design Notes
Scope
Fully analog automatic bicycle front light. No microcontroller, no Arduino, no ESP32, and no firmware.
Implemented blocks
- USB-C 5 V charging-only input with 5.1 kΩ CC1/CC2 pulldowns and input capacitance.
- MCP73831 1S Li-ion/LiPo charger with charge LED and JST-PH battery connector J_BAT.
- External protected 1S Li-ion/LiPo battery pack only; no fixed PCB battery component. BAT_SYS range is approximately 3.0–4.2 V.
- LDR + LM393 darkness detector with adjustable threshold. DARK_OK is intended high when dark.
- SW-18010P vibration switch with 100 kΩ pull-up. MOTION_TRIGGER produces low pulses on movement.
- TLC555 CMOS timer monostable with R_TIME = 1 MΩ and C_TIME = 47 µF, approximately 50 seconds.
- Diode-OR logic combines DARK_OK and LED_CONTROL into LED_ENABLE.
- TPS61165 boost constant-current LED driver powered from BAT_SYS, enabled by LED_ENABLE.
- Two Cree XP-G3 high-power white LEDs in series.
- Test points: +5V_USB, BAT_SYS, GND, DARK_OK, MOTION_TRIGGER, LED_CONTROL, LED_OUT.
Important implementation note
The requirements contained a conflict: strict 555 RESET control by DARK_OK would block motion-only operation in bright conditions, while the later requirement explicitly requested OR logic. This schematic prioritizes the explicit OR logic: LED_ENABLE is asserted if darkness OR motion timer output is active. The timer RESET is tied enabled to BAT_SYS.
Production notes
- Use a protected Li-ion/LiPo battery pack or add a dedicated battery protection circuit before production.
- Confirm TPS61165 sense resistor and compensation/output values against the exact selected LED current target and LED Vf bin before layout.
- High-power LEDs require thermal management: copper area, thermal vias, or an external heatsink.
- Replace RV_DARK placeholder with an actual 100 kΩ trimmer potentiometer footprint before PCB layout.
- The MOSFET low-side switch was included per request, but the preferred high-quality control path is the LED driver EN/CTRL input via LED_ENABLE.
Scope
Implemented blocks
Important implementation note
Production notes
