Overview: the general problem of a small flashlight in general is that the battery life is too short. According to statistics, the average flashlight power consumption is about 2 watts. As shown in figure LED flashlight, the electricity consumption is only 4 24mW, 5 alkaline battery can provide more than 80 service (which means that the sustainable use of 1 months) although the brightness of this flashlight is very limited, but for ordinary road lighting is enough.
Working principle: the core of the LED flashlight is a 7555 integrated circuit (not use ordinary 555). A white light emitting diode (if you can not find, can only use other colors instead) when the brightness of the issue is about 400mcd, so when the focus can be lit 30 meters away.
The focus is to install a short focal length focusing lens in front of the LED.
If you want to use other voltage values, the value of the resistor R3 must be modified: 9V – 470, 12V – 560