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FBTA
Fake Bike Theft Alarm
This
fun project gives you tips how to safely charge a 3.7V Li-ion battery
with a USB charger and guide you how to blink a LED efficiently.
The idea of this project is to install a flashing LED inside the end of a bicycle handlebar. This may scare a thief and prevent the bike from being stolen. You only need to make a hole in the grip for the LED. Typically a handlebar inner diameter is 19mm, The PCB needs 18m. 
Blinking LED in a bicycle handlebar I
am using a
800mAh/3.7V Li-ion
battery,
size 14500 (AA).
The estimated operating time is abt 6 moths after the first cycles.
There
seems to be available also a 1500mAh LI-ion battery model. You
can easily
recharge
the battery via the USB-C connector. The red status LED is indicating charging
and the green LED is lit when the battery is fully charged.
The blinking LED circuit is a Schmitt trigger oscillator which drives a LED by means of a N-MOSFET. 
The charger is using a Microchip Li-ion CC/CV (Constant Current/Constant Voltage) charger IC. It provides preconditioning, constant current and finally safe constant 4.2V voltage charging until the current is low enough, which after it stops charging. The IC provides also status LED drive for charge and full charged condition. See more in the schematics. Downloads - Schematics - BOM - Layout - Gerber files Update 2025-01-21 OH7SV Back to other projects |