Dan's Data letters #158
Publication date: 5 January 2006.Last modified 03-Dec-2011.
Or in a hatbox in your wine cellar
Can I store a laptop battery in a Tupperware container in my pantry or fridge? Why or why not?
Is it a good or bad idea to store my laptop battery in a Tupperware container in my pantry or fridge?
Do you have any better suggestions?
Reason: I have a Sony PCG FX390P. It's an older laptop (P3, 1.1 GHz, 256MB RAM, 15" LCD, DVD/CD-RW, 54MBps wireless PCMCIA card, WinXP Pro installed over Win2000) with a modular bay where you can put in a second battery instead of a weight-saver or floppy drive. The batteries are billed as high capacity lithium ion. Because it's an older machine, I don't usually get much more than an hour of battery life. So, I want to either get a modular bay battery or a second battery, to extend the mobility usage.
When I'm not using the batteries, I am thinking of storing them somewhere, but am not sure what the protocol for storing laptop batteries is. I live in San Francisco in the US, and it is a moderately humid climate. I know you can store Energizer and Duracell batteries in the fridge, but I'm not sure about laptop batteries.
David
Answer:
Yes, you can store a battery in Tupperware in your fridge. You can also store it in a box made of Lego on your roof,
or in a burlap sack at the bottom of a well.
(Smart aleck mode: Off. Or as close to off as it ever gets with me, anyway.)
The general rule for rechargeable lithium batteries of all kinds is to not buy more than you need right now, on account of their lousy lifespan.
Various companies keep coming out with promises about amazing new lithium-based batteries that'll charge in a second and a half, last for eight billion cycles and have the exact same form factor as a shoelace, but none of those have hit the market yet.
If you keep LiI batteries cool and partially charged, they probably will last significantly longer in storage than they otherwise would. I've talked about this sort of thing before, here and here (and then, of course, there's this, and this peripherally relevant page).
The batteries still aren't going to last terribly long compared with plain old NiMH and, especially, NiCd batteries, but every little bit helps, and it's not as if you have to spend a lot of time or effort to store them this way.
When you mention Energizer and Duracell batteries, then yes, you can store them in the frige safely too, but there's not a lot of point to doing it. The natural self-discharge of alkaline batteries at "room temperature" (where "room" is not "outside-toilet-in-Tehran") is only a couple of per cent per year, so you're unlikely to notice much difference. If the alternative is storing them somewhere that's 30 degrees C or warmer, though, then you are likely to notice a difference.
Dry cell batteries ("heavy duty", "super heavy duty") self-discharge faster than alkalines, and benefit more from refrigeration. A lot of people seem to have forgotten about dry cells, which is a shame because as long as they're fairly fresh when you buy them, and run time isn't critical and the load isn't large, dry cells can be much better value than alkalines.
Dry cell batteries have a water-paste electrolyte that should be more resistant to freezing damage (electrolyte expands, battery casing bulges or something breaks inside...) than the water-and-NaOH electrolyte in alkaline cells, but you still shouldn't store either in the freezer. There's just not much to be gained that way over putting them in the above-freezing part of the fridge.
Lithium cells (now available as 1.7 volt AAAs as well as AAs, as well as all of those little coin cells and 3.6V photo batteries) have very low self-discharge and don't really care what temperature they're stored at, within reason.
It's a better idea to store NiMH and NiCd batteries in the fridge, if self-discharge is an issue - they can self-discharge a few per cent per day soon after charging. Though you can, of course, also just pop "stale" batteries back in the fast charger for ten minutes to top them up.
Lead acid batteries of all kinds also have low self-discharge and don't need to be stored cold. Not that I suppose you're considering smashing your fridge's vegie crisper with a crusty old truck battery, but lots of photographers, for instance, tote around sealed lead acid batteries as a cheap power source for their lights.
Nothing beats a Fisher-Price Corn Popper
I have a two-year-old son, and he has a bunch of very, very annoying toys. I've hacked a few of them by muffling or totally removing the speakers, but am wondering if there is not another option.
Would it be feasible to stick a resistor (variable or otherwise) inline with the piezoelectric speaker to reduce the volume? What is the easiest way to go about determining the voltage/amperage that drives these speakers so I can go and talk to Mr Ohm about his Law?
Or am I barking at the wrong forest?
Ben
Answer:
It's nice when all you need to do is put a piece of tape over a grille, isn't it?
Yes, you could use an in-line resistor. Piezos are weird little things, but pleasingly easy to work with.
Electrically, a piezo transducer looks like a capacitor. DC just won't flow through one, and these transducers will work as a high-pass filter for AC, as well.
For its operating frequency range, though, a piezo tweeter passes current more or less like any other. It doesn't have a nominal impedance in the same way that a normal moving-coil speaker does, but in noise-per-watt terms you can think of all normal hi-fi piezos as being like ordinary eight-ohm-nominal tweeters already connected to a suitable high-pass filter (which'll be part of a crossover, in a normal multi-driver speaker). The filter frequency's rather high and so is the efficiency, but there's nothing strange about driving piezos beyond that. This, and their natural resistance to overload damage, is why piezos are popular with makers of PA speakers, and beginner loudspeaker hobbyists. You can just wire the darn things right across a bass driver with no crossover at all, and get a speaker that works pretty well (though it'll probably have too much treble, and the bass driver will still be getting higher frequencies that it can't reproduce properly).
The piezo transducers in toys are cheaper and nastier (though sometimes you find something unusual - I used to have a modem with a piezo about three inches across in it!), and are likely to be driven at higher voltage than the ones that're used in hi-fi tweeters. Easy enough to tell, though; set multimeter to AC volts, touch probes to solder blobs on piezo, see what it's getting when dismantled toy makes a noise.
You shouldn't expect the thing to behave vastly differently from any other nominal-eight-ohm device for volume-control purposes, though. Put eight ohms in series with it, and you may indeed roughly quarter its output power - because now it's got half as much voltage across it, and half as much current flowing. The circuit's power is now actually only halved, not quartered, but one-half of the power is now silent heat from the resistor.
Since the power rating for toy piezos is minuscule, no tiny resistor will warm up even slightly; a cheap lightweight resistance-substitution-wheel doohickey will let you quickly find the right value for the noise level you can live with, or you can of course just buy a bunch of quarter- or eighth-watt resistors with suitably low values and swap them around with alligator clip leads.
In a crossover-ed speaker, in-box volume control has to be done with an L-Pad circuit to prevent the crossover frequency shifting. But if you're just controlling the volume of one driver, you don't have to worry about that.
Alternative, quick and dirty solution: Mechanically quieten the transducer. Tape, non-conductive paint, a blob of glue, chewing gum...
Big feet, little head
I am somewhat of a novice when it comes to taking good pictures. I searched for days on the web hoping to find a solution to a photography question I have, and was thrilled when I came across your article. Particularly because of these two photos in the "Perspective" section.
Basically, I hope to take a picture of a DVD-ROM drive with the tray open. The picture would "emphasize the bigness of the protruding part" (i.e. front bezel) while blurring the back (i.e. the actual drive). This is similar to the photo of the rotary tool that you took. I am hoping to purchase a new lens for my Nikon D70 that will do this job. However, I have no idea which to buy. Searching the web caused more confusion. From what I've been reading, wide angle lenses give the "distortion" while fast 85-100mm lenses give better blur (I might be completely wrong here). Also more confusion was added by knowing the difference in size of 35mm film and the DSLR sensor cause the end result to be different even using the same lens. So, since the pictures on your site are similar to what I want to do, I would really appreciate if you can give me some advice.
Wiyan
Answer:
If you're buying a whole SLR lens, even a $75 piece of garbage, to take just one picture, you need your head examined
- but I presume you know this already.
Since you don't seem to have a really wide-angle lens yet, getting one is of course not a bad idea, and there are lots of options these days. A few years ago it wasn't easy to find a super-wide to match an APS-sized-sensor DSLR, but the popularity of these cameras means we're spoiled for choice in the 15mm-ish range now.
Wide-angle lenses do indeed give the sort of picture you're looking for. The wider the field of view (15mm on a 1.5X-multiplier camera like yours is equivalent in field of view to a 22.5mm lens on a full-frame camera, like a 35mm film SLR), the more extreme will be the perspective "distortion".
The quote marks are deserved, because this isn't really distortion - well, the mere wide-angleness of it isn't, anyway. Rectilinear wide angle lenses just give you an image that can only be viewed "realistically" if you're closer to it than usual. Put your nose up against a photo taken with a full-frame camera with a 12mm lens on it and, assuming your eyes can actually focus that close, it'll look like a normal view of the world.
Fisheye lenses, on the other hand, actually do distort the world in an obvious way - but, personally, I quite like fisheye distortion.
Find examples, with nudity, here.
And yes, you are wrong about needing any particular focal length of lens to get a nicely blurred background. (Probably because you read something about taking traditional portrait photos with blurred backgrounds, for which lenses around the 100mm mark are often used, simply because they let the photographer stand a sensible distance away from the subject. You can also take a perfectly good portrait with a giant telephoto or a much wider lens, though, environment permitting; only if you use a super-wide will your subject look weird.)
All other things being equal, depth of field becomes smaller as the subject gets closer. When you're doing real close-up work (within spitting distance of the subject), it's easy to make the front of it sharp and the back of it blurry by using any large-ish aperture, even if you're using a consumer digital camera with a very small sensor. Smaller sensors give more depth of field from a given lens, which is a good thing for happy-snaps but makes arty selective focus difficult, unless you cheat. The f3.5-ish setting that's the maximum wide angle for all sorts of cheap DSLR lenses is more than enough to blur the background for an extreme close-up shot, though.
The focal length of the lens doesn't make much of a difference here, since to fill the frame with a subject of a given size you have to hold the camera closer when you've got a wider-angle lens, and wide angle lenses have more depth of field. It more or less evens out.
Photo enthusiasts often get all excited about the quality of out-of-focus areas of the image, but if all you care about is quantity of fuzziness, as it were, any lens will do. And the fuzziness looks broadly the same for every lens, unless you're using something odd like a reflex lens.
So you've got two basic options: Buy a super-wide-angle lens of one kind or another, or just buy a wide angle (or even fisheye) adapter that screws onto the filter threads on one of the lenses you've already got.
If you don't think you're going to actually be doing a lot of wide angle photography, and if you don't need a top-quality result, get a screw-on adapter. They work, and they give you a cheap way to mess around with silly effects. You'll lose a fair bit of image quality, but lousy quality can be a feature, not a bug, for a lot of art photography - and if your application involves small prints or scaling images down for the Web, the lousiness can end up invisible anyway.
If you're determined to buy an actual super-wide lens, things can get pretty expensive pretty quickly. I think the only cheap-ish option open to you is the Phoenix/Tamron/Tokina/Vivitar/DatsubishiGrapefruit (almost exactly the same lens under the various names, all actually made by Cosina) 19-35mm f/3.5-4.5 zoom, the Phoenix version of which is the cheapest (yes, from a real store) at $US160-odd, whether you want the Nikon-mount version or one of the others. This lens doesn't go that wide, and it's optically pretty ordinary, but it's confortably better than a screw-on adapter, and apparently quite good value.
The next step up, and the cheapest really super-wide option, and as far up as I'd recommend you ever step unless you've got buckets of money and/or are very sure that much wide angle photography lies in your future, is the very one you saw in the biglens picture - Sigma's 15-30mm F3.5-4.5 EX Aspherical DG DF PDQ QED BLAHBLAHBLAH. It's a big bug-eyed monster of a lens and costs about $US450 (with, again, various mounts available), but it's optically good, and not that big by real compensating-for-something-photographer standards. It's a mere 615 grams, so it doesn't even need its own separate tripod!
Beauti ul music
A friend of mine is a bit of an audiophile (always strikes me as a bit of a Nasty Description, that, not too distantly related to other kinds of 'philes, but I digress). He's worked in the sound and home entertainment industry for many years and with a lot of stuff he really sounds like he knows what he's talking about and I appreciate his opinion. However the other day he was talking about some $120 TOSLINK cables, and was telling us How Much Better they sounded. I laughed and said he must be joking, that digital data transmitted optically either gets there or it doesn't – spending more than $15 on a standard link TOSLINK is an absolute waste of money. He disagreed and said that with a lower quality cable you can lose data that is repaired with error correction, resulting in poorer sound.
Now correct me if I'm wrong, but if you're listening to a CD (or audio DVD) and you lose data bits, somehow, due to a "lower quality" cable, don't you end up with clicks, pops or a complete absence of sound, depending on your equipment and how it handles the data loss? AFAI was aware, with digital media you're either getting the whole data stream, or if it becomes unsynced or corrupt there is NO question about it. Am I totally off track here, or does my friend need a refresher course in digital media connectivity solutions?
It seems to me that audio is an industry where there's a lot more voodoo going on and a lot less science. Personally I find that a bit confusing - being a tech industry, I would have thought the people in it would DEMAND scientific evidence and justification. I mean, sound in all its forms is measurable well beyond what the human ear can perceive - why don't we have labs with audiometers testing scientifically whether cable A improves the sound quality over cable B etc? Why isn't there an audio website with a central, seachable database that proves and debunks various voodoo cable/speaker/amplifier/wooden volume knob myths?
A friend of mine once connected the demo speakers in a sound lab up to the secondary channel from the amplifier using 500m rolls of EXTREMELY cheap cable (you know, your 4c a metre rubbish that ships with $15 car speakers). Yes, that's 500m rolls for EACH speaker, and he said you couldn't tell the difference between that and the $400/m 3m cable that was connected on the primary channel. He demonstrated it in a blinded test to all the sales guys there too, and they couldn't believe it. Its an example that's sold me - I know enough not to buy cable that can't handle the current you're trying to pass through it, but I'll buy a $50 cable over a $400 one if they both do the job any day!
Trevor
Answer:
Your friend's error correction idea is an excellent theory, with only
two minor flaws.
One, PCM digital audio streams don't have any error correction, and two, PCM digital audio streams don't have any error correction. Now I realise that technically speaking that's only one flaw, but I thought that it was such a big one that it was worth mentioning twice.
There's error correction on CDs, and I don't know the details of error correction for the compressed movie audio formats, but it's important to remember that error correction in the disc reader is separate from error correction (if any) in the digital data link from the reader to the separately-boxed decoder/DAC.
In the case of a CD player feeding a digital interconnect, the player does its best to get the right bits - or, at least, inoffensively interpolated bits - off the disc, but after that the data's on its own.
If your digital connection's dropping bits then it certainly can affect the sound of the system, but, as you say, it's rare for a digital interconnect to be less than perfect in such a way as to make an audible difference, without that audible difference to be that there just isn't any music any more, or at least that the music's cutting out and/or hideously distorted. That's the nature of digital data - it's generally either perfect, or very obviously broken. It doesn't handle data loss as elegantly as analogue.
At this point, audiophiles usually launch into an explanation involving detection thresholds and clock jitter and so on and so forth, but that's irrelevant too, because it's all stuff that happens before, or after, the cable. All the cable has to do is move the bits; all it can do to them on the way is attenuate the signal somewhat.
Attenuation can be significant for optical cables once the cable starts getting pretty long. There are various factors to consider then, and cheap TOSLINK cables have a plastic lightguide, which is no good for cable runs of more than a few metres - actually, I can believe that the very cheapest ones could start crapping out at rather shorter lengths. Cheap and nasty cables are also more prone to connector or lightguide damage if they're not treated very carefully - which they may not have been by the person who put 'em in the box at the factory, for all you know.
Digital audio isn't a very demanding task anyway. Since even maximum bit rate DTS audio - which may or may not be used on any DVDs - only needs 1536 kilobits per second (a bit more than the data rate of uncompressed CD audio), and most DVDs require less than a third of that data rate, for regular digital audio cable runs of a foot or two you can pretty much use a piece of clean string.
On the subject of the demand, or lack thereof, for science in the consumer audio industry - I'm sure some of the companies involved care about it a great deal. But industries have customers, and it's their demand, as steered by the shadowless blank-eyed man-things with marketing degrees, that drives the product development decisions. Since psychoacoustic factors are powerful, and the audio reproduction industry long since passed the point where most listeners cannot actually be more satisfied with the sound of the system, the manufacturers were forced to move into less quantifiable factors, whether those factors actually existed or not.
Some of the further development has been very worthwhile. The continuing advances in portable players and headphones, cheap-ish car stereos and boom boxes that can play MP3 CDs, user interface improvements, multi-room audio and so on. And bells and whistles qualify, as well; I'm not a fan of mini systems with indifferent sound and a million blinking lights, but if someone likes the idea of a Starship Enterprise stereo and is happy enough with the sound, then good luck to them.
But real advances only go so far, while the ability of human beings to fool themselves is pretty much limitless. I'm sure that some of the hi-fi snake oil merchants know they're scam artists, but justify their activities on the grounds that gullible people with fat wallets are going to spend their money on some damn thing they don't need. If the "audiophiles" were going to give the money to charity, they would have already. They'll probably get more joy out of a pile of hi-fi crap than they would out of an obscure supercar that spends 96% of its life in the shop, and it's not as if hi-fi scammers are robbing the poor.
Well, that's how I'd justify it if I were in that business, anyway.
Why isn't there a site with a database of reviews of goofy hi-fi tweaks? Because snake oil enthusiasts reject empirical testing, preferring a heady mix of faux skepticism and self-important subjectivism. They're unsinkable rubber ducks, like a lot of believers in the paranormal; the ad hoc explanations flow thick and fast when countervailing evidence is presented.
Anyone who wanted to run a site like the one you suggest would have to pay an awful lot of money for voodoo devices to test, since it's not as if he'd get free review product (well, not after he put the first few reviews up, anyway...). He'd also have a dickens of a time finding anyone willing to advertise on the site - the makers of Acme Medium Duty Figure 8 Bell Wire, "Just as good as Monster Cable!", probably aren't too interested in selling speaker-cable lengths of their stuff at a buck profit per unit, even if audiophiles can be talked into buying it instead of electrically-identical-at-audio-frequencies stuff that makes its manufacturers a thousand bucks per unit.
And, on top of that, such a site would be boring to run. How many double blind tests that end up supporting the null hypothesis would you like to organise per week?
On the one hand, at least the audiophile nuts aren't likely to declare holy war on anyone about the directionality of cables or how much better CDs sound after you've frozen them. But, on the other, he who's happy to believe one crazy thing for no reason is likely to be happy to believe another; the frequently heard "Where's the harm?" argument falls down there, as it can be argued that all irrational beliefs, no matter how apparently innocuous, help to pollute the world with yet more nonsense and make the truth about anything harder to find.
I'll restrict myself to only one James Randi link, at this point.
