LED Torch Circuit Diagram: 80x Longer Battery Life

Circuit Diagram

A prevalent difficulty with miniature flashlights involves a limited operational duration, both for the batteries and the light source. The typical incandescent flashlight, for example, typically draws approximately 2 Watts. The LED Torch depicted in Fig. 1 utilizes only 24 mW, resulting in over 80 times longer performance from 4 AA alkaline batteries – effectively providing up to one month’s uninterrupted operation. Despite the flashlight’s modest illumination, it remains quite adequate for lighting a pathway for pedestrian movement.

The LED Torch is constructed around a 7555 timer operating in oscillating mode (do not employ a standard 555 timer). A white LED (Maplin order code NR73) generates 400 mcd of light output, which, when concentrated, can brighten objects at a distance of 30 metres. Explore Conrad Electronic for a potentially more powerful white LED (order code 15 37 45-11).

A converging lens with a short focal length is positioned before the LED to concentrate the beam. If streaking is observed along the beam’s periphery, utilize another short focal length lens directly in front of the LED to refine the beam.

Should a different power supply voltage be desired, the value of resistor R3 is adjusted as follows:

Integrated Circuit Description

The 7555 timer IC is a versatile integrated circuit commonly used in oscillator and timing applications. It’s a monolithic integrated circuit fabricated on a silicon substrate and packaged for easy surface mount installation. This particular IC operates in astable mode, meaning it generates a continuously oscillating signal without the need for an external trigger. It features three terminals: Pin 8 (VCC), Pin 5 (Trigger), and Pin 6 (Output). Its low power consumption and relatively simple control requirements make it a popular choice for a wide range of circuits. The IC is available from various distributors like Mouser Electronics or Digi-Key.