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Coffee House => Coffee House Boards => CH / Science and Technology => Topic started by: KennyR on August 23, 2004, 10:52:53 PM
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Flashlights (torches, in UK): they're the thing you don't need 99% of the time, but when you do, you need them badly. It's storing the things that's the hard part. Or rather, storing them with batteries installed.
After being caught short needing a flashlight for the last time, I bought one or two, put in brand new batteries, and hung them up in a place I'd always know where they were. A month later, I needed one, so I went for it...and the batteries were practically flat. I know batteries discharge naturally, especially in warm places, but not that quickly.
How can I store these things without the batteries discharging? Sure, I could store them seperately, but that's hardly very convenient if I'm in suddenly the dark or need the flashlight for something quick like looking behind furniture. Is there a clever trick someone knows to store them but keep them ready?
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@ Kenny...
Kinetic torch, my mate
http://shops.bizarsoftware.com.au/ATAShop/catalogue/category16/category78/product174
The mode of operation may remind many users here of their first sexual experience, but the benefit is definite light at the end of the tunnel and no need to buy batteries. Gets you out of a fix at least... :-D
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Hum,
my favourite is candles (http://www.primitiveways.com/fire.html),
(er, though not recommended for looking for gas-leaks), but handy in post nuclear apocalypse eventuality.
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X-ray wrote:
Kinetic torch, my mate
http://shops.bizarsoftware.com.au/ATAShop/catalogue/category16/category78/product174
The mode of operation may remind many users here of their first sexual experience, but the benefit is definite light at the end of the tunnel and no need to buy batteries. Gets you out of a fix at least... :-D
:-D I already have one, hanging up beside my other flashlight. ;-) It's just not very bright. Good enough for finding other flashlights in the dark or not breaking my neck, but not very useful generally, especially outdoors. And it's one of the brightest of the kinetics.
Squatting at the window in the dark frenetically pumping some small rod-shaped object is liable to attract attention too, I suppose. :) (Luckily, my flashlight uses a pump handle, not shaking, yay. Much less onanist.)
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Blob, one biggish problem with candles:
(http://www.firesurvival.com/Images/burningHouse.jpg)
Apart from the fact that the wind blows 'em out when you go outside. And the fact that I can never find matches to light them. ;)
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Hum,
i see what you mean...
but,
it would be cool to be able to see in the pitch black, huh?
(http://files.slonov.net/files/film/Pitch_Black/wallpaper/200/Pitch_Black_005.jpg)
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@ Blobzie
This one here will give you a run for your money in the humming stakes:
http://www.lboro.ac.uk/research/susdesign/InfoInsp/Inspiration/alternate-energy/baygen-torch/baygen%20torch.htm
It's also good for those who don't feel comfortable with the 'shake' motion, or for ladies (whose shake muscles are not as developed) :-P
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Ah, the Sherpa. I know it. I wish I'd have seen it before I got my own kinetic, it looks pretty good. Although, I'd like to know just what 'superbright' actually is. The one I have was advertised as this too. :-P On the other hand, mine is LED, which, while far more efficient, isn't as bright as a xenon bulb like that on the Sherpa.
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@ X-ray
Hum,
not too impressed...
But
if they had it mounted on a head-band then i would definitely get one ...
(http://images.backcountry.com/images/items/medium/PTZ0044.jpg)
BTW, i once had russian ex-military radioactive tritium night lights for my bike once ...they were always on, you just removed the cap to see...
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Nice hat, but I bet its batteries still go as flat as three-week old Irn Bru if left inside.
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Flashlights suck, I use a propane lantern.
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@ Blobzie
That headgear looks like something a 1930s gynaecologist would have.
I think the wind-up torch is probably the best of the bunch.
Tritium-coated sights can still be found on many tactical small-arms, but obviously in much smaller quantities than you would have on your bicycle.
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X-ray wrote:
The mode of operation may remind many users here of their first sexual experience
<>
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KennyR wrote:
Squatting at the window in the dark frenetically pumping some small rod-shaped object is liable to attract attention too, I suppose. :)
:roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao::roflmao:
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I keep a glow stick in the fridge for use in an emergency.
Chemical light is the best!
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T_Bone wrote:
Flashlights suck, I use a propane lantern.
I had one, but threw it away. The mantles were too difficult to maintain. Besides, they can't throw a beam, and looking for the remote control down the couch is liable to be quite an experience with one.
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Seriously though, I'm thinking of just dumping alkaline and going for NiMH rechargables instead. Problem is, they have a lower voltage per battery (1.2 compared to 1.5). Well, thats not the big problem. The big problem is that packaging for every flashlight I ever bought screams: "Only use alkaline batteries in this product!" They don't recommend it, they demand it. Anyone know why?
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Alkaline batteries have higher current densities and are less likely to leak than other disposable batteries. They probably don't suggest rechargables because they don't output the power and hence results in a lower brightness. Also, rechargable batteries (lead acid excluded of course!) generally don't cope with higher current demands well (OK, these things are relative, but a normal bulb drains a lot more juice than most battery driven components), so you get a dull beam that doesn't last too long - not exactly what they are trying to sell.
There is no technical reason not to use non-alkaline batteries I can think of.
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Karlos wrote:
Alkaline batteries have higher current densities and are less likely to leak than other disposable batteries. They probably don't suggest rechargables because they don't output the power and hence results in a lower brightness. Also, rechargable batteries (lead acid excluded of course!) generally don't cope with higher current demands well (OK, these things are relative, but a normal bulb drains a lot more juice than most battery driven components), so you get a dull beam that doesn't last too long - not exactly what they are trying to sell.
You're right apart from the current demands; NiMH is better under high drain than alkaline. But not the kind that flashlights will give. :)
NiMH also has a nice flat output, and can punt out just as much current until its drained. It doesn't tail off, so no yellowing of bulb light (not that I get any anyway, my flashlights are all LEDs). That in itself presents a problem: the current drain from LEDs is so low that its really not much more than just leaving the batteries inside and not turning it on! I'm not sure NiMH likes that kind of job. In fact I'm pretty sure it doesn't.
I could recharge NiMH every 30 days so I'd never have problems. At this rate, I'll be replacing alkaline every 40 without ever using the damn things!
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KennyR wrote:
T_Bone wrote:
Flashlights suck, I use a propane lantern.
I had one, but threw it away. The mantles were too difficult to maintain. Besides, they can't throw a beam, and looking for the remote control down the couch is liable to be quite an experience with one.
Remote control? Do you have a battery powered TV, or just no living room lamps? :-)
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KennyR wrote:
You're right apart from the current demands; NiMH is better under high drain than alkaline. But not the kind that flashlights will give. :)
Well, that's kind of what I was hinting at. Didn't realise NiMH was flat output. Thats interesting - the internal chemistry must be quite funky ;-)
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Hum,
what is flat output?
A steady flow of electrons, er, as opposed to wave-like output?
BTW, has anyone actually made a battery here?
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blobrana wrote:
BTW, has anyone actually made a battery here?
Sure. I made some interesting cells when I was mucking about in labs. Tried to see how far apart in the electrochemical series I could get to get a large EMF...
Never could find an ionizing solvent sodium wouldn't simply reduce. Apart from liquid ammonia, but then it just dissolves in that ;-) Pretty colour though ...
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Hum,
So kenny could have all the bits he needs to make a battery in a kitchen cupboard....pre-prepared in advance so he just need to `insert the cathode` type thing for it to work...
i found this handy table (http://www.efunda.com/materials/corrosion/electrochem_list.cfm?sort=com) for him to experiment with
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So is that, what a flat output is?
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Uhm, all one needs to make a battery is an orange and a zinc and copper plate from what I remember.
For a school project we once considered a bunch of spuds in serial. But that couldn't deliver enough current ;-).
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Ok, done some research into NiMH batteries, and I'll think I'll do the switch. They may only be 1.2V compared to alkaline 1.5V, but apparently alkaline lose EMF quite quickly and they average at 1.2. NiMH give a much more even discharge, which is useful since the flashlights don't have current regulators and go dimmer as alkaline drain.
And most of all I don't need to keep replacing them. If I charge them every two weeks I won't have to worry about leakage or hydrogen gas buildup. No arguing with the energy density though - alkaline still kick NiMH ass, so I wont get my 900 hours of light. Pity but not the end of the world, unless it really does come to the end of the world. In which case I'll loot a shop and get alkalines. :)
Ladies and gentlemen, you may keep your primitive combustion products and homemade voltaic piles. I'm going rechargeable.
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Greetings,
@KennyR
:idea: Why not change the flashlight bulb to something efficient to say, small but powerful LED, like what most mobilphones have, only brighter, and something very reflective on it's side for best illumination.
Very little power needed and smaller in size. Man, you can even use a AAA battery. What do you think?
Regards,
Gizz
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gizz72 wrote:
Why not change the flashlight bulb to something efficient to say, small but powerful LED
None of my flashlights actually have bulbs. They're all LEDs. But actually providing light isn't the reason I keep running out of batteries, it's the drain the flashlights have when not on that's freaking me out.
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@Kenny
What sort of LEDs are they?
It's not necessarily good, but ultra bright red (>15,000 mcd) draw a tiny current (20mA or so). Ultra bright green types draw a bit more current (but not much more), and green is perceptably much brighter than red to the normal human eye.
"White" LED's AFAIK draw considerably higher currents at the same luminous intensity...
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@Karlos
They are white (although they look slightly bluish), and they are brighter than most ordinary flashlight bulbs. A Lightwave 4000 (with 10 white LEDs) which is advertised to run with 900+ hours on 3 D batteries, and a Lightwave 2000 (4 white LEDs), advertised for 340 hours on 3 AA. Actually they'll probably still be bright enough to read by long after that. So they ain't high current! ;-) (The LW4000 is probably the world's most efficient flashlight, and I had to ebay for it and get it stateside.) Oh, and my kinetic, with its purple LED that seems to be lit no matter how long the thing is left on. :) But isn't very bright. :(
LEDs rule, but they have one important failing: they don't throw a beam. Further than 10m, they're useless. Thats why some manufacturers are making hybrids with both xenon/halogen bulbs and LEDs. LEDs for ultimate battery economy, bulbs for long distance.
It seems even the world's most efficient flashlight still suffers from parasitic drain. :(
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@Kenny
Yeah I know that they aren't current hogs compared to conventional bulbs :-) However a superbright red LED (harder to see though) would probably give twice the battery length. A green version would look far brighter to the human eye and still last maybe 60% longer than white LEDs.
Still, try selling a green torch :-D
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Hum,
i suppose that
If kennys ancestors had evolved on different planet orbiting a different coloured star then his eyes may more sensitive in other wavelengths,
But for humans i recon it's red, blue and yellow.
@Kenny
Ever considered keeping your batteries in a fridge? (In sealed bags of course)
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blobrana wrote:
Hum,
what is flat output?
A steady flow of electrons, er, as opposed to wave-like output?
BTW, has anyone actually made a battery here?
I built a fuel cell, a simple Hydrogen Oxygen Bacon cell. I used 8 molar Potassium Hydroxide at 60 degrees C as the electrolite and nickle as the catalyst/electrode.
My Supervisor was not happy about boiling Potassium Hydroxide... and was really not happy about 8 molar bubbling away.
I built the chasis of the fuel cell using perspex (acrilyic) and used Araldite to bond the pespex.
The potassium hydroxide disolved most things, including the araldite, the perspex and the skin on my hands.
My aim was to develop a practical Methanol Fuel cell, but I ran out of time, just trying to over come the problems with the Hydrogen Oxygen cell.
The electrolite was poisioned by water produced int he reaction which reduced the efficiency after about 15mins.
I got voltages as high as 1.1volt, but I nover got the current above 5miliamps... this was probably due to the relativly small surface area of my catalyst.
Thus ended my quest for a nobel prize :-)
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The Band gap required to produce Blue light is HUGE.
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bloodline wrote:
The potassium hydroxide disolved most things, including the araldite, the perspex and the skin on my hands.
What, boiling 8M KOH attacked the stuff? Now there's a surprise :-P
You should have used a pure petroleum wax coating inside the case, obviously choosing one with a melting point higher than your operating temperature. KOH wouldn't have eaten it...
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Assuming it was aqueous KOH and not alcoholic, of course ;-)
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blobrana wrote:
Hum,
i suppose that
If kennys ancestors had evolved on different planet orbiting a different coloured star then his eyes may more sensitive in other wavelengths,
But for humans i recon it's red, blue and yellow.
Green mostly, we can detect greem better than any other wavelength, given that we're not colorblind :-)
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Colour blindness has nothing to do with green receptivity. It so happens the monochrome cells that make up the majority of the retina respond to light in the green/yellow region of the spectrum. Those cells aren't used to judge colour, only brightness, hence we see green as brighter than other shades regardless of wether or not we percieve the colour itself.
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Given the spectral class of our sun (G2/Yellow), this makes perfect sense - we'd be hopeless if we depended on eg far red for our overall brightness information :-)
-/edit-
Trust me, I'm extreme red-green colourblind ;-)
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Karlos wrote:
However a superbright red LED (harder to see though) would probably give twice the battery length. A green version would look far brighter to the human eye and still last maybe 60% longer than white LEDs.
There are green torches out there. You're quite right in that green LEDs are both more efficient and mostly useless, but wrong that they would look brighter. The human eye sees about 1/3 of reflected green light, while it sees 2/3 of white. Have a look at this Q&A (http://flashlightreviews.home.att.net/qa.htm) on the flashlight review site.
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Blobrana wrote:
Ever considered keeping your batteries in a fridge? (In sealed bags of course)
I don't really have to go to those extremes: alkalines lose about 2% charge per year somewhere like a drawer. But fridge or drawer, they're not in the flashlight where I want and need them. I could go with X-ray's suggestion and fumble about with my kinetic to find them, but then I wouldn't be properly ready for armageddon. ;-)
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bloodline wrote:
The Band gap required to produce Blue light is HUGE.
It's no big deal. You just plug the band gap with a suitable dopant.
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@Kenny
I meant that green would appear brighter than red (thinking along the single wavelength LED approach) :-D
Naturally white would appear brighter still since it is the sum of all wavelegths...
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[color=33CC00]@Karlos
Hum,
Interesting,
Though i suspect that T bone is also correct in that it`s a yellow-green colour that we are most sensitive to (er, cos the yellow `band` is very narrow).
but, er, i`ve never bothered to look, in depth, into the mechanics of the human eye.
[/color]
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but, er, i`ve never bothered to look, in depth, into the mechanics of the human eye.
It's more Chemistry than Mechanics...
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@blob
I'm sure I said yellow/green in that last post ;-)
@bloodline
Maybe she meant Quantum Mechanics, in which case she's spot on ;-)
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Hum,
yeah,
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Anyway , i noticed T bone said `greem`... :-)
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blobrana wrote:
Anyway , i noticed T bone said `greem`... :-)
:-P
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Hmm, I got a battery tester and the batteries aren't as flat as I thought. They're sitting at something like 85% capacity.
Still, thats not 100%, so out they go and in go the NiMH. The old ones can go in a drawer to await the end of civilisation, where I can barter them for virgin brides.
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KennyR wrote:
Still, thats not 100%, so out they go and in go the NiMH. The old ones can go in a drawer to await the end of civilisation, where I can barter them for virgin brides.
How many Virgin brides does one get for half dead A cells?
-Edit- /me quickly rushes to the junk draw in the kitchen to dig out old batteries :-D
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bloodline wrote:
KennyR wrote:
Still, thats not 100%, so out they go and in go the NiMH. The old ones can go in a drawer to await the end of civilisation, where I can barter them for virgin brides.
How many Virgin brides does one get for half dead A cells?
-Edit- /me quickly rushes to the junk draw in the kitchen to dig out old batteries :-D
None, if someone shows up with working C cells :-P
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Coincidentally, I found 3 rechargeable C cells that have been lying at the bottom of a box since before 1990, and they actually still took a charge. I was pleased, before I realised that I don't have one single item made to run on them. That's why they were at the bottom of a box for 15 years.
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KennyR wrote:
I don't have one single item made to run on them.
A likely story! :lol: ;-)
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Perhaps it explains his -uhm- slightly negative outlook on the world :-D.
:angel:
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:lol: