LED Torch

The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears to be a stronger white LED (order code 15 37 45-11).

A convex lens with short focal length is placed in front of the LED to focus the beam. If banding occurs at the beams perimeter, use another very short focal length lens directly in front of the LED to smooth the beam.

The circuit design of the LED torch incorporates a 7555 timer IC configured in astable mode to generate a continuous pulse width modulation (PWM) signal. This configuration allows for the effective control of the LED's brightness and flicker rate, enhancing the versatility of the light output. The 7555 timer is preferred over the conventional 555 timer due to its improved performance characteristics and stability in various operating conditions.

The white LED, specified with Maplin order code NR73, delivers a luminous intensity of 400 millicandela (mcd), which is sufficient for illuminating objects up to 30 meters away when combined with an appropriate optical system. For applications requiring higher brightness, the alternative LED from Conrad Electronic (order code 15 37 45-11) is suggested, as it may offer superior performance in terms of light output.

To optimize the light distribution, a convex lens with a short focal length is utilized, positioned directly in front of the LED. This lens concentrates the emitted light into a focused beam, allowing for effective long-range illumination. In scenarios where beam banding is observed at the perimeter, the addition of a second, very short focal length lens can mitigate this issue by smoothing the beam profile, resulting in a more uniform light output.

The overall circuit design should include proper power supply considerations to ensure that the LED operates within its specified voltage and current ratings, thereby prolonging its lifespan and maintaining consistent performance. Additionally, appropriate heat dissipation measures may be implemented to prevent thermal buildup, which can adversely affect both the LED and the timer IC.The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears to be a stronger white LED (order code 15 37 45-11). A convex lens with short focal length is placed in front of the LED to focus the beam. If banding occurs at the beams perimeter, use another very short focal length lens directly in front of the LED to smooth the beam.

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