LED watch I wish existed

Max

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This is a watch idea that has been rolling around in my head for a while, and since I'm not about to do anything about it myself, I just thought it would feel good to get it off my chest and see whether anybody else thinks it's a good idea too.

I prefer wearing an analog watch, and I like watches that light up good and don't need button pushes to turn on the light. That's why I have watches with tritium tubes and watches with generous amounts of Super Luminova on them. I even have ones with both /ubbthreads/images/graemlins/wink.gif.

The problem is that while tritium tubes are bright, they are not actually that bright. Freshly charged Super Luminova is much brighter, except of course, the glow fades to being dimmer than tritium after not too long.

There are a couple of watches out there that use LEDs to illuminate the dial, like this Casio:
MTD-1048A-1A1.gif


and this Dakota watch:
82831.jpg


But they still are activated by pushing a button.

I think that using a LED to splash light across the face of the dial is not the best way to go.

I saw one of these blinky lights one day:
ledsupply_1831_3149442.gif


and I noticed that when you take the lens off of an LED, the little glowing chip in there is really pretty small, and while a teeny one might not throw a lot of light, it's really pretty bright to stare right at it. Actually, the glowing part of the little chip itself is no bigger than one of the tritium vials in a watch, and I'll bet it wouldn't take much current to light up an LED to be brighter than a tritium vial.

What if you made a watch that used 12 little bare LEDS for hour markers? How much power would it take to light up that watch face brighter than a Luminox all night?

Here's what I would do. I would start with a solar-powered watch like a Citizen Eco-Drive. The watch uses its solar cell to recharge the battery/capacitor and also to measure how much light is hitting the watch face. If it's a lot of light, then the LEDs are turned off and the batteries recharge. If it's only a little light, the LEDs turn on. For power savings, you could make it so that, for example, the LEDs turn on dimmer in complete blackness than they do in low light because it's harder to see a dim glow in dim light than it is to see a dim glow in the total absence of other light. In addition, you could make the LEDs shut off after say 24 hours or when the power is running down so that the watch doesn't quickly go dead when left in a drawer.

Of course, you could add a button, for the heck of it, that when pushed turns on the LEDs full bright for 5 seconds.

Seriously, how much would this extra power draw reduce the power reserve of a solar watch that normally runs in the dark about 6 months fully-charged.

Some things I haven't figured out yet. Is there a good way to light up the hands? What about the date?
 

KevinL

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It depends on how many milliamps you are running through the LED. 5mm LEDs run around 20-30mA, which is a HUGE amount of power for such a small watch. But at 20-30mA, we are looking at the power of an ArcAAA or CMG Infinity Ultra. For a watch, that is truly a huge amount of light. Heck the watch could double as a flashlight, although the batteries would go flat faster than you can say "that was bright".

However, it would be possible to light a LED at much lower currents and still produce light. You're right, the actual light emitting semiconductor die is extremely small and could be easily encapsulated near or as part of one of the digits, minus the epoxy dome of 5mm LEDs. Driven at low current, it would already put out more light than glow material or tritium.

A cool idea: combine the LED with strontium aluminate (the compound behind many high end glow-in-the-dark materials) - so that you only light the LED for a second, enough to charge the glow material, which continues to glow after the LED has been extinguished.

On a less technical note, I was looking at a watch the other day without an integrated backlight - I'm used to digitals like the Casio G-Shocks and their EL backlight. Then I realized, why do I need a backlight? My backlight has a variable power selector dial, six levels of output, runs from a lithium ion or two CR123s and has a Luxeon V emitter /ubbthreads/images/graemlins/grin.gif
 

DBrier

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I think you could get better results in both the compactness and power levels if you used a tiny led and some fiber optic cables. Twelve cables and and a single LED should work quite nicely.
 

Max

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[ QUOTE ]
KevinL said:
A cool idea: combine the LED with strontium aluminate (the compound behind many high end glow-in-the-dark materials) - so that you only light the LED for a second, enough to charge the glow material, which continues to glow after the LED has been extinguished.

[/ QUOTE ]
Yes. I like that idea too. Use blue or UV LEDs with glow material. Green or red LEDs would probably be more power efficient.
 

Max

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Teaneck, NJ
[ QUOTE ]
DBrier said:
I think you could get better results in both the compactness and power levels if you used a tiny led and some fiber optic cables. Twelve cables and and a single LED should work quite nicely.

[/ QUOTE ]
Or some kind of one piece plastic light guide.
 

BF Hammer

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I think the idea can be taken even farther. A single UV LED with optical fibers running to behind markers on the dial that have a coating of Luminova. A timer circuit briefly flashes the LED at regular intervals to charge up the lume and keep it charged up to high brightness. UV light will transfer higher-energy photons to the lume and will need shorter flashes for charging up. An on/off button or maybe even a motion sensor could be added so it is only activated while the watch is worn, making less demand on the battery.

Some of the technology from the Citizen Eco-Drive series could be applied to make these solar-powered. Hmmm...I'll think of ways to make this thing cost over $500 yet. /ubbthreads/images/graemlins/broke.gif
 

Max

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Actually, I'll bet OLEDs would be really good in an application like this. I have read that in displays they light up for microamps per pixel. Anybody know if OLEDs are more or less efficient than semiconductor chip LEDs?

They wouldn't need to be any brighter than that. OLED displays are visible in a room with the lights on. Tritium vials are not.
 

GiveMeLight

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Feb 18, 2005
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Iowa
This might be up your alley...

How about a watch with 138 LEDs (red, green, and yellow)?
Solsuno LED watch
Solsuno Web site

I have no affiliation with either site. -Just a passion for technological excellence /ubbthreads/images/graemlins/smile.gif
Cheers,
Gabe
 

cheesehead

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Re: This might be up your alley...

If you need more light than that of a luminox with their tritium tubes, well,...I don't know. I've never found a situation where ambient light wasn't enough, or when the tubes weren't bright enough. The lighting on that watch is darn near perfect, and in a dark room, it's nearly bright enough to read with.

All the "glow" watches I've had were horrible. They are brighter for about 30 seconds and then are just plain terrible. The pulsed LED to charge them, sounds good, but again, can this be any brighter than tritium tubes and can a watch contain enough battery power to make this practical? I would guess not.
 

cobb

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Re: This might be up your alley...

Wonder if timex makes a dial face watch with the indiglow surface? Seems that would about cover your needs. I like my timex iron man with that technology. It is evenly bright and readable. I use to uave casio watches that used an actual bulb to side light half of the screen, but use that too much and you ran down the battery.

What I would want is an led watch , either dec or binary that stayed lit and maybe you plugged it in to a pc or a wall wart to charge it.
 
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