Re-call in my youth if you turned down the dimmer switch in my room the switch became warm to the touch and made a loud buzz. Interpreted this into ‘hmmm, reckon it’s not saving energy, just wasting it. Oh hum, best look at boobs in the catalogue’

Few decades later and I recently purchased cheap ebay head torch;

http://www.ebay.co.uk/itm/Ultra-Bright-500-Lumen-CREE-Q5-LED-Headlamp-Headlight-Zoomable-for-Outdoor-UK-/161069509583?pt=UK_SportsLeisure_Camping_LightsLanternsTorches&hash=item25807dabcf

Now, for £8 it’s ace for dog walking/emergency uses, really impressed however, when I dimmed the light on it the other day I recalled the catalogue light in my room and wandered if there was in point turning down the light strength if it did not save battery power.

Does anyone know much about the model/electrics to school me? There is no noise/noticeable heat when dimmed.

It will be using less energy.

Not an electronics bod, but I think that the driver will be:

– restricting the current to the LED, so rather than e.g. 6v @ 750mA, it’ll be 6v @ 500mA. Power=volts*current so lower volts and/or current will result in less power consumed.

OR

– it’ll be a PWM signal, where the LED is effectively turned on and off very rapidly. High brightness might be 80% PWM signal (80% on, 20% off), whereas low brightness might be 50% PWM signal, so the LED is on for less time, but at the same brightness when it is on. The on/off occurs so rapidly, that you can’t perceive it.
EDIT – PWM stands for Pulse Width Modulation.

Wait for someone to tell me how wrong I am now…… 😀

Cheers stumpy, you’ve backed it up with numbers so i’m willing to accept what you say as FACT!

Ta muchly

Ride in the rain and the strobe effect on raindrops is obvious.

scotroutes – Member

Ride in the rain and the strobe effect on raindrops is obvious.

I’ve noticed that before, but is that not just caused by the number of drops passing and being momentarily illuminated, then the next one, then the next one….?

I think PWM signals are in the kHz or maybe even MHz range……would be impossible for the human eye to detect. I think.