Dan's Data letters #117
Publication date: 16 July 2004.Last modified 23-Aug-2012.
22.3V, tolerance 0.4%...
I was wondering if you know a site where you can get an Australian power supply outputting 9V AC 1.5A, the plug at the end looks to be around 4mm in diameter. I've checked at Jaycar and DSE, they both didn't have it and couldn't really point me anywhere either.
Minh
Answer:
As you've already discovered, this is an unusual specification and not easy to find.
It's entirely possible that the gadget you want to run doesn't actually need AC. If it's got an internal bridge rectifier, then you should be able to connect a regulated DC adapter with a big enough current rating to it and have it work; even the polarity of the input won't matter.
If the thing runs from DC but does actually use the AC waveform for some reason (like running a timer, for instance), then plugging DC into it is still unlikely to even pop a fuse - the device just won't work.
There are devices in the world that run from AC plugpacks and don't like DC; they have an internal transformer to provide different voltages to different parts of the device. Plug DC into a transformer and you'll blow it up. Small plugpack-powered devices aren't very likely to work this way, though; gear with internal transformers usually runs from mains power. Damage is much more likely to happen if you plug an AC adapter into a gadget that wants DC than the other way around.
Anyway, if the thing really needs AC, then you may be reduced to scrounging around for some random beefy 9VAC power supply on eBay, probing it and giving it a new plug, or just building a regulated supply yourself. Old C64 and C128 PSUs are a good 9VAC source for people who need something to run that old modem, or whatever (and give you a bonus 5VDC rail as well), but even the C128 PSU can only output about one amp at 9V, so that's no good for you.
Solid state off-roading
Is it possible to make a long-range LED light for use as off-road lights? It seems that the best way to do it would be to mount the LED shining into the housing of a large flashlight and let the light reflect off the housing and back out, but I'm not sure.
Eli
Answer:
In theory, yes, but it's not economical yet, because you can't get single LEDs that're bright enough (well, unless
by "off-road lights" you mean "off-road bicycle lights", or something).
White LEDs manage around the same luminous efficacy as halogen incandescent lamps; they're considerably less efficient than the HID (High Intensity Discharge) mini-arc lamps that're currently popular in headlamp and after-market automotive light applications. Since long-lasting LEDs that can handle more than about five or six watts continuously don't yet exist, you need a cluster of LEDs for any automotive headlamp kind of application, which'll cost you a lot of money even before you start looking at the optics to use with them. Most narrow-beam LED applications use lenses in front of the LED, but side-emitting Luxeon lamps (and, now, some cheaper clones) can be used with conventional reflectors.
If and when the dollars-per-lumen of super-LEDs becomes competitive with that of HID or even plain old incandescent, then they'll be practical for mass market headlamp kinds of applications. Right now, though, they're only suitable for money-no-object concept cars.
Conductive tyres not included
I was wondering what your opinion is on the "Earth Grounding Kits" you can buy for performance cars. People (usually the those selling them) say they provide small power gains (2-3 kilowatts), improved "stability" of the electrical systems, better audio, brighter lights, and other general benefits in all areas. The most common comment is improved "smoothness". Measure that!
So anyway, by all reports they're "good fer what ails ye!"
HKS even make a kit, and they generally make high quality performance parts, which makes me wonder if maybe they really are beneficial in some way. I can get a kit quite cheap and try it out, but mum taught me not to waste, so I thought I'd ask your opinion.
Ryan
Answer:
On the face of it, it sounds ridiculous to be tying the grounds of various pieces of car electrical equipment together
with an earthing kit, since by definition they're all tied together by the chassis of the vehicle, in any normal negative-ground
automobile.
However, it's not so silly when you consider the lousiness of the earth connections that various devices may have. Most notably, the battery itself in many cars often has less than perfect clips on its terminals - corrosion is common between the clips and the wires that're crimped into them, thanks to the proximity of sulfuric acid. And other things can have bad earth connections too, if there's rust or slight looseness. The connection may look OK when you apply a multimeter to it with the car stopped, but may become crummy when the engine's running.
Most of the people who buy pre-packaged grounding kits, though, are going to install them in a vehicle that's already been dressed up to some extent, and is probably either pretty new or, at least, well-maintained. In these cases, everything should already have a decent earth - or can be given one for free, by unscrewing the contact bolts and cleaning out any corrosion, muck or paint that's between the metal surfaces. If all your battery currently has is one dinky old corroded cable connecting its negative terminal to the chassis, there could be some justification to replacing that with a foot of super-chunky wire and cleaning the contact points, especially if you're running a big stereo and/or lots of after-market lights. But as far as the full earthing kits go, only if you're adding that bling-blingy decorative copper octopus to a car that's not actually in a good state of repair - which I'm sure some people are - is it likely, to my mind, that you'll be achieving much.
Let's humour the earthing kit people, though. What could a kit do?
If all you're talking about is simple DC loads like amps and headlights, I think the improvements people report from extra earthing have to exist only in their minds, unless something was wrong (in a way that could be fixed without extra hardware) in the first place. Bad car stereo installations may have a bad earth path, restricting the current the amplifier(s) can draw. So may badly installed after-market light kits. So may the factory components, of course, and not necessarily only in cars made in England. But, generally speaking, adding parallel earth wires for that sort of gear ought not to achieve anything.
Electronic equipment like engine control computers and their networks of sensors are a different matter; they may well Go Strange if their design assumes a clean 12/13.8V supply but they actually get something glitchy and fadey. Any well designed electronic device should be immune to all normal power input weirdness, of course (which is why super-fancy power conditioning devices for stereo systems, especially very expensive power cables, are such a stupid concept), and the automotive industry's been using electronic control systems for long enough now that they ought to know what their gear is at all likely to be fed. But then again, these things are built down to a price, and even in performance cars a percentage point or two of engine power is going to be very hard for the user to detect, even on the drag strip. If that's all the car makers sacrifice by not running their own fat earth cables all over the place, they may be perfectly happy with the situation.
For this reason, I find reports like this one, which found a massive 1%-or-so gain in peak dyno power with an earthing kit, plausible enough. The complexity of the engine management system, in a modern tweaky performance car, is sufficient that improving the earthing may well actually do something.
If people were claiming really noticeable gains then I'd be very suspicious - if bad earthing was costing 40 horsepower, the manufacturers really would have noticed - but the marginal gains reported, assuming they're not just testing errors, aren't ludicrous.
The above-linked page also talks about how to make your own earthing web, by the way, much cheaper than a pre-packaged one that comes with a rice boy sticker.
Boiling's no good either
Concerning your recent response on the life of Li-I batteries in mobile phones (and in general), a friend of mine heard that you can rejuvenate them by sticking them in the freezer for a few days. He didn't think it would work, but his battery was next to useless anyway, so he tried it as a last resort. He claims it did noticeably improve the battery's performance.
Benjamin
Answer:
The freezing point for lithium ion battery electrolyte is below -20°C, so a normal domestic freezer shouldn't actually
damage them (it may damage lithium polymer batteries, though), but there's no reason to suppose it'll do them
any good, either. Perhaps the fact that your friend just left the battery alone for a while let it perk up a little.
If there's actually anything you can do to revive a dead Li-I pack, nobody's found it yet.
Wiggy wall warts
I have a problem regarding AC to DC adapters (mobile phone chargers, actually).
I have recently moved to Brazil from Sweden, and I brought my mobile phones and other electronic equipment. The thing is, the electricity works differently here. In Sweden, a standard outlet has one 230V phase at 50Hz and a neutral, and ground if it is a grounded outlet. Where I live in Brazil they have two phases with 110V each (60Hz) and sometimes ground (although my measurement just now showed 122V on one phase, 114V on the other). No neutral. In my head this should equal more or less 220V, 60Hz.
My problem is that some of my AC-DC adapters work, while others supply a way too high DC current. I noticed it only after my Siemens mobile phone battery died, presumably from having charged it with twice the intended voltage for some time.
My Sony Ericsson charger that is rated 100-240VAC 50/60 Hz with 4.9V output works just fine. My Siemens charger is rated 220-240VAC 50/60Hz (and therefore should work) but outputs 8.9 V instead of the intended 5V. My Nokia charger is rated 230VAC 50Hz, and it outputs 7.9V instead of 3.7V. All measurements are without load.
That the Nokia doesn't work I presume is because the frequency here is 60Hz and it is only intended for 50Hz. But the Siemens? Is it because of the two phases without the neutral, or what? Should I invest in locally marketed AC-DC adapters for my electronic equipment to be on the safe side?
I also succeeded in killing the DC adapter for my router, which was rated 100-240VAC, 50-60 Hz, but that may be unrelated to the problem above (it could have been a sudden surge in the power grid or something, it was before I invested in a good power filter).
Jan
Answer:
The "phase-phase", no-neutral mains power arrangement you describe is not at all common. Well, it's common in the
USA in houses that have a phase-phase 220V supply to run clothes dryers and other high-power devices, but not many
countries use it for general purpose mains. If an oddball mains system is used anywhere, though, it'll be used in
Brazil, where it would seem that every local government has its own idea about what kind of mains to use.
That said, though, I don't know why some of your adapters are freaking out and others aren't. It's certainly not because you're testing the adapters without a load; mobile phone chargers should all be regulated and not deliver significantly higher voltage when they're unloaded, and unregulated adapters shouldn't ever deliver more than root-two times their rated voltage, anyway.
Perhaps the aggregate phase-phase voltage is more than 240V - apparently single-phase power of up to 127V is used in some parts of Brazil. if you've got an RMS AC voltmeter, it'd probably give you a decent idea of the aggregate voltage if you put it across the two phases, unless the waveform is extremely screwy. I'd be more inclined to expect problems from the surges and spikes and sags that're common in countries like Brazil (I'd definitely invest in power conditioners for everything in sight if I were you), but that wouldn't account for some AC adapters being consistently nutty, and others not. Maybe a reader will clue me in about this.
The supply frequency could perhaps have something to do with the problem, for the Nokia charger, but it ought not to cause a high output voltage; inductive loads don't like being run at a higher frequency than the one they were designed for (going the other way is generally OK), but a modern switchmode plugpack (the lightweight ones that phones always use these days, as opposed to the bigger, heavy, transistor-filled linear plugpacks that cheaper gear commonly still uses) shouldn't be too bothered about it, and certainly shouldn't go that crazy. Maybe the higher mains frequency is overheating it, and then it's freaking out - if it goes crazy as soon as it's plugged in, though, that's not the problem.
Should you buy a bunch of new adapters? Maybe. Find local nerds and ask them. And I mean local nerds, not ones from the other end of the country who may have a whole different collection of electrical problems to deal with.
Magic bulbs
Since you've discussed Compact Fluorescent Lamps before, I was wondering what your take was on the Fresh2 Odor-Eliminating Light Bulb?
Joe
Answer:
I took a little while to answer this letter, because when Joe sent it to me, I had no opinion about these allegedly-deodorising
CFLs beyond the natural miserable cynical skepticism that suffuses every molecule of my being whenever I'm presented
with anything that promises a tiny reduction in the soul-demolishing
awfulness of the human condition.
Now I'm willing to believe that the things work, though.
It continues
Here's a $US2000 power cable for you!
But that's cheap compared to the one at the bottom of this list.
Then there's this.
I can't believe (well, I guess I can, but I'd prefer not to) that people will pay $US6800 for a Siltech Cables "Golden Eagle Signature G6" 1.5 meter DIGITAL interconnect cable. Lord knows the bits won't get there any other way...
But back to the $US6700 Siltech "Ruby Mountain Signature G6" power cable. I could get a pretty good (yeah yeah, not "audiophile") system for that kind of money.
If only I had lower ethical standards, I would start a business selling this kind of crap (but more expensive), claiming my cable was assembled with filtered machinery (haven't seen anyone claim that yet). Moreover, the cable itself would be made with hand-picked atoms and molecules - each tested to ensure they have no quantum signatures that could distort the audio path. Yep, I'd have to reject 99% of the atoms that came in the loading dock, but I'd still make a fortune only selling 5 or 6 a year. Especially selling something like the $US32000 10 foot Siltech "Emperor Signature G6".
I weep at my morality...
Danny
Answer:
[Deem my usual arm-waving wild-eyed rant about such cables to have been included here. Oh, and as of 2012, the Ruby
Mountain Signature G6 has been superseded by the
Ruby Mountain II, which lists
for a mere $US6500
or so, depending
on length. Siltech's "Emperor
Crown" speaker cables can be found for only
$US35,000 for
two 2-metre cables. But if you're really serious about your music, the "Emperor
Double Crown"
cables are
only $US48,500!]
To be fair, you certainly could get an audiophile stereo system for $US6700 - or for quite a bit less. The lunatic fringe of the audiophile market does not define everybody who's happy to call themselves an audiophile, any more than Christians who believe in treating acute appendicitis with nothing but prayer speak for Christians in general.
(And there are also definite audiophile lunatics whose particular brand of lunacy just doesn't require them to spend a lot of money.)
The word "audiophile" has, indeed, come to be associated with people who, rather than listening to music through the hardware, listen to the hardware through the music, and seldom seem to be satisfied with what they hear. But lots of audiophiles have quite modestly priced systems. There's a whole culture based around cheap speakers that can be built at home, often mildly obscure things like single-driver transmission lines (maybe with a tweeter perched nakedly on top), or corner-loaded horns (which can be pretty expensive if you buy 'em built, but you get a darn solid piece of furniture for your money). And there are also plenty of audiophile cults based around vintage hardware of one kind or another - the little old BBC LS3/5a monitor speaker, for instance, or various home-made tube amps of highly variable merit.
These less hardware-fetishistic audiophiles may still blow epic amounts of money, but they generally do it on obscure vinyl and/or CD collections visible from space.
Regarding your brilliant plan to milk cash out of the other audiophiles, though - I like it! But the tooling should all be made of aluminium bronze and beryllium copper, so you can not only proudly claim that your entire plant is non-magnetic, but that no sparks are ever struck in there, to corrupt the cable with the evil of broadband radio frequency interference!
(Metal sparks and electric sparks aren't actually the same thing, but I think you should be proud if you can add your own little particle of audiophile flapdoodle to the mountain that already exists.)
