I will explain how to use j.t. circuit with bicycle light and convert it to efficient and relatively cheap source of light.
First you need small ph screwdriver to disassemble leds and electronic switch board (circuit).
Electronic switch cant be used with 1,5 volts or less so we are going to dismiss it and use small lever switch.
Cut out plastic peace to make room for the lever switch . You can use sharp knife, scalpel, sandpaper or dremel with sanding stones, as you can see in pictures i like to use small chisel which ive made from old screwdriver and piece of sandpaper for finishing
Using soldering iron take out leds from the original board.