[Laser] Modulated LED light

[stuart.wisher at talktalk.net]

I was interested to hear of the pulsed LED radiation from the apartment. In addition to switch mode PSUs for LEDs, (frequency sounds way too low to be one of those), some time ago I used to use the red light coming from car tail lights equipped with LEDs some 6km away to test my AM baseband optical receivers. It seems that many LED rear lights on cars are pulsed at audio frequencies, plus the bi-xenon headlights on other cars also make an interesting sound. One of my friends has a car where the LED tail lamps are pulsed at a different frequency to to the stop lamps. Also, those cars that have interior lamps that fade down before they go off completely, emit an interesting noise as they do so, it is obvious that some sort of PWM is employed to achieve the fading by progressively reducing the duty cycle.


Stuart, G8CYW