Idea to extend LED runtime

[mobile1]

Here is an idea to extend LED-runtime, I dont know whether someone has already come up with this or whether a LED light is using this already or whether it would work at all.

The characteristics of a LED is that they provide instant light (in less then 100ns - which is if I am not wrong about 10^-9 seconds).

My idea now is to instead of delivering a constant current to the LED, to deliver short pulses of current, which turn the LED on and off at a very fast rate - When there are more then 20 light "flashes" per second, our eyes think it is a constant light (sort of like a movie where you see multiple still-pictures and you think its a film).

My guess here would be that it should be possible to save a percentage of energy - the time the LED is off. It also would generate less heat.

Of course I dont know whether this would decrease the perceived brightness.... but maybe not, because it takes the eye a certain time to adjoust to darker light. Think of it when looking into a flash, the flash seems to last a lot longer (in our eyes) then it actually does.

Does anyone have some equipment to test this assumption... perceived brightness vs. energy consumption of a fast-strobe LED-Light.

 

[georges80]

It will look dimmer - that's essentially what PWM is all about - a dimming mechanism that provides constant current pulses of variable duration (to maintain the same colour temperature of the white LED/phosphor).

You will of course extend battery life - but the LED will dim. I have a version of my uFlex driver (test software) that does dimming via PWM rather than lowering the drive current.

george.

 

[INRETECH]

There is no magic bullet here, the human eye is VERY slow and will see the average of the light output

I had a customer convinced this would work, and I did tests and showed him that it doesn't

 

[mobile1]

thanks - thats what I love about this place - lots of knowledge...

 

[Roy]

Eternalight uses this (or did) in their lights that have a dimming feature. My Eternalight Marine works this way!

 

[koala]

If you PWM the wrong way.. ie, slow hz, you will drive some minds crazy, some people get dizzy, vomit and so on. I've seen it /ubbthreads/images/graemlins/frown.gif.

 

[AilSnail]

I think at around 11hz some people can get epilipsia - very serious stuff. I'm not certain about that frequency, though.

 

[sgtgeo]

Wow that could be fun at parties.

I can see it now...."bet you can't look at my flashlight without having a seizure"

lol

 

[Steelwolf]

Hey Sgtgeo. Seizures are no fun at all. Very frightening for the person undergoing it because your mind is still awake but your body won't respond. And the spasms are quite painful too.

There were quite a number of reports of kids having seizures because of some computer game. Not sure about that though.