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Flashlights that use Light-Emitting Diodes (LEDs) instead of traditional incandescent bulbs are becoming popular these days, mostly because they generate light much more efficiently, so they use less power and the battery lasts longer. However, so far as I've seen, just about all these flashlights have
multiple LEDs in them, to produce light.
I'm sure the manufacturers do this so that they can advertise that the flashlight is as bright as what people are used to, but in my opinion, I don't always want or need that much light--and the battery could last even longer. Some of these flashlights have a voltage adjustment feature that can dim the LEDs together, some have a focusing adjustment that can concentrate the total light into a narrower/brighter beam, but neither of these is what I want.
I'd like to be able to control the number of LEDs that are actually emitting light. A very simple slide-switch could accommodate this easily. Let's assume a flashlight that has 4 LEDs:
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The above sketch portrays one horizontal wire that doesn't touch the 4 vertical wires. Each of the 4 wires connects to a different LED. (The rest of the circuit connects to the battery, and we need not portray that.) Let's assume the slide switch (not portrayed) is at the right. No LEDs are lit. As we slide the switch to the left, it allows a connection to be made between the first of the vertical wires and the horizontal wire, so now 1 LED is lit. A fairly standard thing called a "detent" can be incorporated to let the user know that the switch has been slid to a place where it won't slide by itself off of that spot.
The detent doesn't prevent the user from forcing the switch to slide to the next detent, where 2 LEDs would be lit, because of the physical length of the conducting part of the slide switch. Obviously if we slide the switch all the way to the left, all 4 LEDs will be lit.
There are other ways to accomplish the goal of adjusting the number of glowing LEDs (rotating switches, electronic switches controlled by a single pushbutton, etc.); I just haven't seen any flashlights yet on the market, that allow this adjustment.
9-Volt LED Light, with two intensity settings.
http://www.amazon.c...s06-20&linkCode=asn
This can keep its LED continuously lit dimly for at least a year. I've placed mine in strategic places, such as at the top of a staircase -- very useful in the event of a power outage. [Amos Kito, Dec 11 2008]
50w led driver
http://www.linear.c...,C1094,C1766,P81080
[n81641, Dec 17 2008]
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Sorry, baked for some time now.
I've got one with ten LEDs, the first press of the on/off switch puts on six of them, press two puts on all ten. Press three turns them off. I've had this one maybe five years now. |
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I've seen bicycle lights (mostly the red tail lights) that have a single switch that can cause various things to happen to the LEDs (off/on, steady glow, flashing in different ways, etc). But like I said, I haven't seen an ordinary flashlight with this adjustment. I'm not surprised that it exists; I'm just surprised that they don't seemed to be advertised as having this feature. |
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Mine does that. It would be more useful if it was a better torch, but you always need it on brightest. They tried though. |
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As I say, it's a few years old now, and uses multiple 5mm LEDs; modern lights tend to use fewer, more powerful LEDs, even single devices - you can buy Maglite LED replacement "bulbs" that are brighter than the incandescent lights, and last longer.
Maybe have a PWM device to control brightness for these, but difficult to retrofit. |
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Good quality LEd lights have an inbuilt control module that regulates current across the LED. This is quite selectable - I'm yet to see one with fully analogue controll, but I do have a torch at home that has 11 power settings. Basically a full depress of the tail button is on/off, and a half depress toggles through the settings. I think there are 9 settings for light intensity, then there is a strobe setting, then there is a SOS - programmed strobe. |
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This control methodology (solid state, built into the control module) is very common with high-end LED torches and headtorches. I own several high-end LED devices and all of them feature current-regulating control modules and multiple brightness settings. Not that this makes your idea redundant per-se, but I for one prefer solid state switching rather than mechanical. Lastly, LED's preform much better, exhibit better battery life, etc when driven by a control module. You'll find that the more powerful CREE or LUXEON star modules all require a driver to run - you can just bang some volts across the terminals if you like, but don't expect much from them if you do. |
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[Ian Tindale], in the US, the term "flashlight" refers to the same device that the term "torch" refers in the UK. |
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A torch i've had for a couple of years now also does this with one button. Press for one, three or six leds. |
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[marked-for-retention] User living in his own dream world where real world inventions penetrate slowly, if at all. |
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Guys, this idea IS original to the poster. Read the help file, if you doubt me. |
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// I'd like to be able to control the number of LEDs that are actually emitting light // The torch i have does this with a push button. Sorry if i've missed something but how is this idea different? :-) |
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[Ian Tindale], that's where a rotatable knob or a slide-switch could be advantageous. You can quickly move it to roughly the final desired spot, and then tweak either more or less lit LEDs as desired. |
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//it's actually quite technically difficult to vary their brightness - you have to do it using pulse-width variation rather than simply varying the voltage//
It's actually quite simple - being current-driven devices, you vary the current, not the voltage, to vary the brightness.
PWM (pulse-width modulation), which has the effect of varying the average current through the device, is just one way of doing this.
All you're doing is switching off the LED for a different amount of time - do it at a high enough frequency, and all you see is a dimmer or brighter LED (until you move your eyes rapidly) |
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At which point you start fitting. |
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In addition to adjusting the brightness / number, it can be useful to adjust the light color. I have an LED flashlight that features bright white along with 2 ranges of UV. How far away are we from one with adjustable color IR>Vis>UV ? Controls like a graphic EQ... |
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Even relatively cheap LED torches/flashlights have multiple modes these days. I have a couple of Fenix lights that have 12, 53, 107 and 120 lumen output levels and a couple of strobing settings all solid state controlled for about £35. |
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I've made a few flashlights like this, i used 24 bright white led's and the 3 switches allow me 1 for reading while camping, 8 for untangling knots and 24 for when I'm trying to find that hook I dropped while fishing. |
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//How often do you say "You know what? This torch is just too bright."?// Burglars need dim torches. In one Trixie Beldon adventure a burglar puts tape over most of the aperture of his torch, to avoid waking people. Of course, Trixie immediately identifies him as a burglar for this very reason. An excellent feature would be for the first LED to be red, so you can see without ruining your night vision. I put a dimmish red LED in a mini maglite for this reason, when rogaining. I used it to read the map and relied on unaided night vision the rest of the time, and carried a second bright torch in case it was needed. |
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I like the slider switch idea. |
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[UnaBubba], this Idea does not widely exist in the form presented here, where the LEDs are individually switchable. I agree that many of the new lights allow switching of banks of LEDs, but that's not the same thing. Your MFD is invalid, therefore. |
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//individually switchable// The logical development would be LEDs with brightness related as consecutive powers of two, with one switch per LED, enabling binary coded brightness; 2^n brightness levels (including off) for n LEDs. |
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LED's tend to vary in brightness if in parallel, but if wired in series, the current is the same for all, but harder to switch individually. An automotive LED headlight driver circuit I read about runs an entire 55 watt string of LED's in series. I'll see if I can find the link... |
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