march.brown
Flashlight Enthusiast
Many torches nowadays are using Pulse Width Modulation to control the brightness of the LED ... At its simplest , PWM is a series of DC pulses where the gaps and pulses are altered ... The series of pulses can have a mark to space ratio where the pulses of DC are of zero width (no light output) , up to 100% width (full light output).
These pulses are effectively square waves ... A square wave has every odd harmonic of the fundamental frequency up to infinity ... The spring in the tailcap is an inductor ... The impedance of an inductor increases with frequency.
The higher the fundamental frequency , the worse this effect will be ... Is this perhaps one reason why the fundamental PWM frequency is low enough to be heard by some people ?
Would a different type of non-inductive connection at the tailcap improve the performance of the torch by reducing the inductive effect ? ... The design of tailcap springs has not changed significantly since the first torch was invented ... In those days the torch was a simple ON/OFF device using plain and simple DC.
Some of the PWM torches actually create pulses that themselves are made up of several pulses of DC as opposed to just straight pulses of DC ... This would make the tailcap spring inductive reactance even higher , due to a higher fundamental frequency.
Just wondering if anyone else had thought about this !
.
These pulses are effectively square waves ... A square wave has every odd harmonic of the fundamental frequency up to infinity ... The spring in the tailcap is an inductor ... The impedance of an inductor increases with frequency.
The higher the fundamental frequency , the worse this effect will be ... Is this perhaps one reason why the fundamental PWM frequency is low enough to be heard by some people ?
Would a different type of non-inductive connection at the tailcap improve the performance of the torch by reducing the inductive effect ? ... The design of tailcap springs has not changed significantly since the first torch was invented ... In those days the torch was a simple ON/OFF device using plain and simple DC.
Some of the PWM torches actually create pulses that themselves are made up of several pulses of DC as opposed to just straight pulses of DC ... This would make the tailcap spring inductive reactance even higher , due to a higher fundamental frequency.
Just wondering if anyone else had thought about this !
.
