New Idea - Using Strobe to save battery power

CanadianBacon

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I was just got an idea when I saw the specs on the quark aa2
on turbo, the runtime is 1.3 hrs.
on strobe, the runtime is 2.5 hrs.

What if there was a strobe that was above 60hz so that the eye can't perceive the strobe and it looks like a continuous beam.

It would be as good as a normal continuous beam.... but with twice the runtime. If a single die led can't strobe fast enough..... how about having a quad-die led cycling through all four at 60hz+?

Any thoughts?
 

maxotar

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Isn't this essentially the same as Pulse Width Modulation (PWM)? If so, your idea is already in use, just at higher frequencies.
 

UpChUcK

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I was just got an idea when I saw the specs on the quark aa2
on turbo, the runtime is 1.3 hrs.
on strobe, the runtime is 2.5 hrs.

What if there was a strobe that was above 60hz so that the eye can't perceive the strobe and it looks like a continuous beam.

It would be as good as a normal continuous beam.... but with twice the runtime. If a single die led can't strobe fast enough..... how about having a quad-die led cycling through all four at 60hz+?

Any thoughts?

It's called PWM and it is already used to extend runtimes and keep the LED's from :poof:. Some use current control.

Damn, beat me to it.:eek:
 
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joeparker54

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It's called Pulse Width Modulation, or PWM. Many, many, many lights already use it. LED's are capable of pulsing in the kHz range. You can control the brightness by varying the duty cycle.

damn, two beat me to it! lol
 

KenAnderson

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It's being done all the time. Many LED lights use a strobe effect to vary output. Swing a light at arms length while watching the lit LED. If you see gaps, it's stobing. If you see an even swath of light, the circuit board uses a non-strobing method to control output.

Great idea you had, just a few years too late ;)
 

mcnair55

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I was just got an idea when I saw the specs on the quark aa2
on turbo, the runtime is 1.3 hrs.
on strobe, the runtime is 2.5 hrs.

What if there was a strobe that was above 60hz so that the eye can't perceive the strobe and it looks like a continuous beam.

It would be as good as a normal continuous beam.... but with twice the runtime. If a single die led can't strobe fast enough..... how about having a quad-die led cycling through all four at 60hz+?

Any thoughts?

Are you really that bothered about battery life that much? Just enjoy your light and stick another battery in when required.:ohgeez:
 

Kestrel

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The other thing is that the eye will perceive it as less bright overall, so you're still not getting anything for free. Say, a ~50% duty cycle will be only be half as bright, for example - this is dimming via PWM.

It's actually more efficient to draw less continuous current rather than use PWM, as the LED operates more efficiently at a constant 50% current draw rather than 100%/0%/100%/0% etc.
 

adnj

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This is absolutely correct. This is what PWM does.
I was just got an idea when I saw the specs on the quark aa2
on turbo, the runtime is 1.3 hrs.
on strobe, the runtime is 2.5 hrs.

What if there was a strobe that was above 60hz so that the eye can't perceive the strobe and it looks like a continuous beam.

It would be as good as a normal continuous beam.... but with twice the runtime. If a single die led can't strobe fast enough..... how about having a quad-die led cycling through all four at 60hz+?

Any thoughts?
 

Mr Bigglow

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The very first portable LEDs I ever saw were inside inches-across button-type units intended for bicyclists. They were always amber in colour, used 9 volt batteries, and flashed at a moderate speed, about 60 pm, extending the battery life out up to what was then a HUGELY impressive 12 hours. All of which is to say that it's interesting to learn that the 'flash conversation principle' has been extended so far as described.
 

mcnair55

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cool!

I never knew about this "pulse width modulation"

looks like I have a lot to learn :)

And just think in a couple of months time you will be explaining to another newbie and with knowledge gained from here.I have zillions to learn but day by day I do.
 

Linger

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Interestingly, the Dosun H1 seems to msot of what the OP posits.
The 5th mode is a full bright strobe, so quick a flickering that even the most die-hard 'tactical strobe' fan won't call the Dosun 5th mode disabling in any way. I have used the PWM flicker when bushwacking, and it provides a helpful amount more usable illumination then the medium mode. So what's it do?
Well, when the batteries are depleted, all the headlight will do is this quick strobe, flashing away for a looong time, giving users the most possible usable light from the batteries for the longest time.
I posit this is what the mode is for: even with freshly charged batteries, max run time with max illumination. It's the WTSHTF mode, if you know you'll need to hike through the night.

Point two is that, if the pulse on is long enough, the light does not seem dimmer, it is not the same as PWM dimming. The Dosun strobe duty cycle is visible (a few times a second) and 'appears' as bright as high output. High is the first mode, Strobe and High are easily compared as High is the next click away. Clicking to High doesn't appear any brighter, just makes the flickering stop.

To summarize:
OP's totally wrong saying this is a new idea
correct in that strobe can be applied in a way that isn't PWM dimming
incorrect to believe it could be subliminal (+60hz quick pulse below visual threshold) because to fast will appear as dimmer rather then full bright strobing.

Best,
 
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HDS_Systems

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CanadianBacon,

Your eye integrates so a fast strobe will look like a dimmer continuous light.

As is explained on our web site, PWM is significantly less efficient than a reduced current drive from the perspective of the LED. Smooth DC is in fact the most efficient way to drive an LED.

You might want to read our frequently asked questions to gain a much better understanding of LED flashlights.

Henry
 

richardcpf

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In flashlights with PWM, low mode is basically a lower freq. strobe.. same will happen with the quark. It is impossible to increase runtime without sacrificing brightness, it's the law of physics.
 

MikeAusC

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Say you have a direct-drive light that puts out 100 lumens.

If you pulse the power to it, it will draw less power and it will produce less light, BUT the brightness-to-power ratio will be greater.

Say it's on for 5% of the time, it will only draw 1/20th of the power. Because the chip is running cooler it will produce MORE than 1/20th of the light.

If you measure the light with a lightmeter it will still show an average brightness a bit over 5 lumens, BUT if you pulse it at around 60 Hz and you ask people to judge the light's brightness, they'll report it as closer to a light putting out 10 lumens - i.e. it will appear twice as bright as the equivalent power.

This increase in APPARENT brightness is optimised at 60 Hz and 5% duty cycle.
 
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tolkaze

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All i know is, that PWM is only really good for static lighting, or for walking through the bush. Close up work, reading and fast movement across sharp lines (like in the house) makes me sick really easily. Even really fast PWM for reading is annoying, like the pinwheel effect of a DLP projector.

Constant current feels so much smoother when reading, even at the same brightness
 
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