TEA NOW

Teasmade

Alarm clocks are awful. Get one of these instead.

Even if your alarm clock is one of those Zen alarm clocks with melodious metal chimes, or it's your phone playing New Age music at gradually increasing volume, an alarm clock is still not offering you anything. It's just invading your rest and causing you to start your day with a little slap of sadness and irritation, arguably made even worse by the snooze button's empty gift of a few more minutes of half-sleep. Which you'll probably only spend trying to integrate your interrupted dreams with wakefulness.

(It is, at least, pleasant when I realise for the umpteenth time that I am not, in fact, still in high school.)

Or you may just lie there, living in fear of the return of the cursed alarm.

I shudder to think how much human misery those millions of little morning insults have added up to, over the centuries since humans first invented a water clock that would make a noise at a particular time.

Presuming you can't just rearrange your life so it doesn't matter when you get up, the best option in the pursuit of timed wakefulness is, clearly, a butler. A butler who brings you a cup of tea, even as he murmurs his apology for the regrettable necessity that you be conscious.

(The celebrated Stephen Fry alarm clock seems to no longer be in production, and it would also appear that more people paid for them than actually, strictly speaking, received a product in return. One can only hope that the Bible-verse version of the same product is similarly defunct. I would very much like to see a combination of the two.)

Failing that, what you want is a teasmade.

Teasmade

This one's mine. It's not a particularly elegant or collectible example, but it does the job.

The modern teasmade - the term has become a genericised trademark, in Britain at least - is essentially an electric kettle controlled by an alarm clock. When the alarm time is reached, the kettle element turns on, and a few minutes later boiling water is delivered to the tea-leaves.

Or to anything else you put in the little teapot, for that matter. If you want alarm-clock instant soup or Bovril or anything else you can prepare by putting it in a pot and pouring boiling water on it, you can have that too. (Might be a bit of a challenge eating soup out of the little teapot, though, if there are bits in it too big to exit the spout. You could also make a hot-milk-based beverage in a teasmade. But possibly only once.)

Most Automatic Food Machines, especially the ones that look like the coolest thing in the universe, have problems. They don't work in the first place, or they work only for a little while without unfeasible amounts of maintenance, or they're uncleanable, or their sole desire is to maim or murder their operator.

For every good gadget like the blade meat tenderiser or Aeropress coffee maker, there are a dozen crappy As Seen On TV wastes of time and money.

(There's also a small sub-category of wonder food gadgets that can only work by breaking laws of physics.)

A teasmade is not like that.

It is easy for a tired person to set up of an evening, it does what it's supposed to do without fuss, it has no moving parts except the control buttons, and its cleaning requirements are close to zero.

(Classically, you are never meant to do anything more than rinse a teapot; the accumulating tannin stains are supposed to make the tea taste better, though I'm pretty sure that claim doesn't stand up to double-blind testing. If you've got unusually hard water or use a teasmade for a long time then you may also need to clean lime-scale out of the boiling vessel and tube, but just running the teasmade with water and vinegar in the boiler should take care of this.)

Antique brass teasmade

The earliest alarm-clock tea-makers were created in the late nineteenth century. They were shiny and clockwork, with alcohol burners and a match-striker or other similarly implausible mechanism to light the burner when the alarm went off. These devices were less of a threat to life and limb than one might imagine, but were still less than entirely convenient to operate, and also rather expensive. And, to be fair, if there's one thing that'll wake you up even more effectively than a nice cup of tea, it's a fire on your bedside table.

The modern teasmade is electric, safe and reliable, and quite cheap. I bought mine used on eBay in 2003, and it cost me only $AU37.85 delivered. That was an unusually good deal - one just like it is on ebay.com.au as I write this, for $AU90 plus delivery - but working and pretty-safe-looking used teasmades routinely sell for well under $US100 delivered, and you can get a brand new one for less than 60 UK pounds delivered within the UK, $AU160-odd delivered to Australia, or around $US165 delivered to the States. Or less, if you buy the version with no radio, of which more shortly.

And yes, American buyers are likely to have voltage problems, because the teasmade is largely unknown outside the UK and as far as I know nobody makes a 110-volt one. More about that in the "buying one" section, below.

How it works

Teasmade

As you can see in the above picture, the modern teasmade really is essentially just a combination of an alarm clock - often, as in mine, a clock-radio - and an electric jug. It's quite easy to use.

The alarm clock in my teasmade works in the same way as every cheap plastic clock-radio. You set the time, you set the alarm, you tune the radio, and you select how you want the thing to wake you up.

Teasmade controls

In addition to the standard clock-radio options of an awful alarm noise or a tinny radio, though, my teasmade lets you select "tea" alone. You will then be awakened by the sound of boiling water, and the smell of a mildly caffeinated beverage.

My teasmade is rated at 600 watts at 240 volts, which is on the low side by electric-jug standards; here in Australia our mains electricity is a nominal 230 volts and a usual actual 240, so electric jugs with a power rating of 2000 watts or more are common.

My teasmade's water capacity is only about 650 millilitres - that's about 2.6 metric cups. Or a couple of good-sized mugs, or more than three dainty little teacups. The 600-watt heater takes about seven minutes to boil this full capacity; proportionally less if you don't fill it completely. You should of course take account of this boiling delay when setting the alarm time.

The initial heating process is quiet; it'd probably wake me up if I were sleeping without earplugs, since I'm a pretty light sleeper, but most people would sleep through it. The part where the boiling water is transferred to the teapot, though, is quite dramatically loud, and should be an effective alarm for most people all by itself.

The reason for the noise is the way in which my teasmade, like pretty much all others, transfers the boiling water from kettle to teapot. When you put the filling cap back on the boiling vessel, the boiler is sealed except for a metal tube that goes almost to the bottom of the vessel, and arches over to point at the middle of the lid of the...

Teasmade teapot

...distinctive hole-topped little teapot. (If you find a junk-shop teapot that looks like this, you now know where it came from.)

When the water boils, the pressure of the steam pushes the water through the tube and into the pot. It takes no more than ten seconds for my teasmade to transfer a full pot-worth of water through the rather narrow tube. Hence the noise. When the reservoir's empty, it heats above the boiling point of water and a thermostat shuts off the heater. (There's also a switch that disables the heating element if the teapot isn't in place, so night-time absent-mindedness will not result in an unconfined spray of boiling water the next morning.)

If you need more of an alarm to wake you up then, ideally, you'd be able to set the horrible alarm noise or irritating radio station of your choice to go off when the water transfers, or even after the tea's had a few minutes to steep. But my teasmade can't do that; the alarm/radio goes off when the heating element turns on, at which point a single cup of tea is at least five minutes away, and a full pot is at least seven.

Some teasmades have more sophisticated alarm settings, so the alarm can go off when the boiling is completed, not when it starts:

OK, that alarm takes us straight back into the Land of Horrible Awakenings. But at least there is tea.

Going along with its cheap-clock-radio nature, my teasmade has no backup battery, and reverts to that good old flashing "12:00" and no memory of previous settings if there's even a momentary power cut. You can solve this problem by running the teasmade, and for convenience also your bedside lamp, from a small uninterruptible power supply. A pretty beefy UPS will even be able to run the tea-making element; a cheap one won't be able to do that, but will at least ensure continuity of timekeeping if the element doesn't try to click on from UPS power.

I'm hardly an authority on teasmades, though; there are a lot of different models, even if you disregard the pre-electric W. Heath Robinson versions.

Goblin
Teasmade
(Image source: Flickr user James Mooney)

Here's a Goblin with a removable boiler, as well as teapot, presumably for ease of filling.

Goblin
teasmade
(Image source: Flickr user James Mooney)

TEA NOW
button
(Image source: Flickr user Martin Deutsch)

I wish mine had a TEA NOW button.

Teasmade with
trophy
(Image source: Flickr user leo.j.turner)

Another picture of the same model of teasmade, or at least one with the same buttons. It appears to have won an award. Good for it.

Teasmade with
slightly lopsided lamp
(Image source: Flickr user MarkyBon)

This one just screams Fawlty Towers.

Assorted
teasmades
(Image source: Flickr user gruntzooki, a.k.a. Cory Doctorow)

Another just like it, and some others, on display in the London Science Museum. It's apparently circa 1945.

The integrated lamps can be rather nice:

Science
Museum teasmade display
(Image source: Flickr user ebbandflo_pomomama)

Teasmade with top
reservoir
(Image source: Flickr user Simon Harriyott)

This one looks as if it ought to be mystifying Jacques Tati in Play Time.

Buying one

A simple search for "teasmade" (which may or may not correctly geo-target to your country; here the same search is on eBay UK, and here it is on ebay.com) gets 20 relevant hits on eBay.com.au as I write this, plus a few isolated teapots and a Bjork remix with "Teasmade" in its title.

There are some decent deals there, but I probably got my teasmade so very cheaply - under $AU40 delivered - because it was described as "Alarm clock/radio with teapot -RARE", which barely describes it and is almost impossible to search eBay for. I've no idea how I ever found it.

Even if all you throw into the eBay search box is some generic "tea maker" sorts of terms, it's pretty much impossible to filter out umpteen ordinary electric jugs, teapots with infusers in them, teapot-shaped kitchen timers and so on. Here's my best effort at making such a search across the whole of eBay.com.au with possible geo-targeting to other eBay sites; if that doesn't work, here's one for ebay.co.uk and here's one for ebay.com.

The easiest way to get a teasmade today is to just buy one new. For a while I think this may have been impossible unless you found a dealer with "new old stock", but now it's quite easy to buy a Swan teasmade online.

Swan teasmade

You may or may not care for the Swan's magic-lantern styling and LCD analogue clock, but on the plus side, you know the appliance hasn't been sitting in someone's garage for fifty years, maturing into a truly world-class fire hazard.

The Swan teasmades list on their site for £79.99 (about $US128 or $AU124, as I write this) ex delivery. They don't ship outside the UK, though.

The Swan teasmade is also on sale at this Union-Jack-waistcoat of a site, which is very excited to announce that the "Teasmade Classic is now £48.99 and the Radio Teasmade is now £69.99!". But they, also, only ship within the UK.

There are Swan teasmades on eBay; a US buyer could get the basic no-radio model for $US132.05 plus a mildly suspicious only $US6.00 for shipping, and an Australian shopper could get the same model for $US142.05 delivered.

That's not cheap, but at least the Aussie shopper would only need a plug adapter to connect a UK-sourced teasmade to Australian mains power.

(Until quite recently, it was normal for UK appliances to come with a power cable that terminated in bare wires, because the UK contained an incompatible mixture of the old BS 546 and new - in the sense of "after World War II" - BS 1363 wiring and plug standards. You had to buy a plug separately and screw it onto the cable yourself, or get someone in the shop to do it for you if you were a wuss. Nowadays BS 1363 is dominant enough that I think pretty much all UK appliances come with a BS 1363 plug moulded onto the end of the cable. Chopping that plug off and replacing it with one to suit your own country's mains, so you don't have to use an adapter, is unwise if you don't know what you're doing, but is legal in most countries.)

If you live in the USA, Canada or some other 110-to-120-volt country, though, you have a problem. Some teasmades wired for 110V are alleged to exist, and converting one wouldn't be an insoluble problem for an electronics hobbyist or repair-person, but you ain't gonna get one off the shelf.

So there's nothing stopping someone in the Americas from buying a teasmade from the UK or Australia, but it'll be the wrong voltage and you'll have to run it from a quite beefy step-up transformer.

Your beefy step-up transformer will very probably be an autotransformer, and very probably come with a piece of paper listing a wide variety of devices they strongly recommend you never plug into it on account of autotransformers' poor isolation qualities. A teasmade is likely to fall into at least two of those forbidden categories.

That said, two-pin sockets and cheater plugs do not yet seem to have killed most of the American population, and those are more straightforwardly dangerous than a teasmade running from a step-up transformer. Modern teasmades also have no exposed metalwork, so you're not really living too dangerously if you use one from a step-up transformer. I'd do it. But I am known for making poor decisions.

You can also get fully electrically isolated step-up transformers; they're more expensive, but solve the safety problems. And if your American house has a 240-volt circuit for a clothes-dryer or other high-powered electrical appliance, you can just plug the teasmade into that. (Running an extension cord from the one 240V outlet in the bathroom all the way to your bedroom may negate the safety benefit.)

The frequency of US 240V will be 60Hz instead of the 50Hz the teasmade expects, which will cause old-style electric clocks to run six-fifths as fast as they should. If you get an old teasmade with an analogue clock then there's a good chance it depends on the mains frequency to keep time, and will thus be essentially useless from the wrong frequency. You could run it from a frequency converter, but by now we're getting well out into the crazy-weed.

As long as there's no mains-synchronous clock in your teasmade, a different mains frequency shouldn't be a problem. A newer teasmade with a digital clock will very probably have a quartz oscillator that's immune to mains frequency changes.

Alternatives

By this point, American shoppers intrigued by the teasmade idea but disinclined to subscribe to British Appliance-Fancier Monthly will probably be thinking there must be a simpler way to do this. I mean, you could just plug an electric kettle into a timer switch and get something approximating the same functionality.

It occurs to me that if you get a coffee-maker that has a timer function, put tea leaves in it in place of coffee (and, if you want to get fancy, also replace the paper filter with a mesh strainer screen), you could get very close to a teasmade's functionality without all of the international-voltage bother.

The design of the typical modern no-moving-parts bubble-pump coffee-maker (which, incidentally, uses as a pump the same sort of device that propels a pop-pop boat)...

...is not ideally suited to making tea, but it'd more or less get the job done. A coffee-maker may not quite make Tea According To Orwell, but I'd drink it.

(Oh, and cheap drip coffee makers' primary purpose appears to be to make coffee snobs almost as apoplectic as percolators do, but a teasmade actually makes pretty close to optimal tea. It doesn't pre-heat the teapot, which is a mark against it, but it does deliver really scalding water onto the tea leaves, which is generally agreed to be Correct. Coffee benefits from being made with less-than-boiling water; tea does not. The fact that water boils at only 174°F at 20,000 feet {79°C at 6100 metres} is clearly a far greater problem for British mountain-climbers than any piffling shortage of oxygen.)

Cheap coffee-makers with timers require you to reset the timer every night, because they can't tell whether there's already coffee in the carafe or not, and want to avoid disasters that a forgotten full carafe could cause the next morning. (Leaving the water reservoir empty shouldn't be a problem, though, because even the very cheapest of coffee-makers should have a reliable overheat cut-off.)

You'd think you could get a coffee-making teasmade-analogue with an actual alarm-clock brewing function for a reasonable price, but I'm not sure if you can. I think you can do it with expensive plumbed-in models like this one, but few mere counter-top models seem to have such a feature.

I think this inexpensive Black & Decker model may qualify, though. I managed to find a manual for it online and it does seem to have a repeating alarm-coffee function. If you definitely know of such a thing, please do tell us all about it in the comments.

(On the subject of different approaches to the problem, check this out. Once again, some concept designer has supported my previously-expressed opinion of the breed, in this case by reinventing the teasmade and making it much, much worse. Apart from apparently being carefully designed to set itself on fire from the middle out, this concept design expects you to, first thing in the morning, drink tea out of a hemispherical E-Z Spill(TM) cup with no handle. This design also requires you to put a tea bag in cold water the night before and let it sit there for hours before the water is heated, which I can only presume will cause the ghost of Queen Victoria to manifest, reach into your chest and crush your worthless heart.)

The Ministry of Safer Walks

A reader writes:

I have heard on the worksite (construction; I'm working through college as a part-time fetcher and carrier) that if a power line falls, or someone drives a crane into power lines...

...you should move away from the danger site by taking tiny little steps, or even jumps with your feet together.

But I have also heard that I need to go somewhere and ask for a bucket of compressed air, or a "long weight", or a box of right-handed pipe elbows, on account of we only got left-handed ones here.

Is the pogo away from the power line thing just another way to make people look stupid? Doesn't the electricity get grounded into the... ground?

Jay

Oddly enough, this is actually good advice. It may not be necessary in a particular situation, but better to look a bit of a dick and survive than stride away in manly fashion and die.

It's all about the voltage gradient. Connect a power line to ground by cutting it or leaning some metallic object against it and the electricity doesn't just magically vanish at the contact point. If the contact point were an actual earth stake driven deep into the ground then even a quite major power-line short pretty much would disappear right there, but if all you've got is some cable draped on the ground, or big voltages buzzing to earth in scary arcs from this and that part of the frame of a piece of construction equipment, then it's sort of like pouring water onto level ground. Some soaks in at the point where it hits, it spreads out and some more soaks in, it spreads out more and even more soaks in, et cetera.

In this analogy, voltage maps to the depth of water on the surface. The closer to the contact point(s) a given piece of ground is, the higher the electrical potential at that spot will be. This is where the analogy breaks down, though, because you will come to no harm if one of your feet is in two inches of water and the other is in one. If one of your feet is on a piece of ground charged to twenty thousand volts and the other is on a ten-thousand-volt spot, though, you'll have a ten-thousand-volt potential from foot to foot, and you'd better hope your shoes have thick rubber soles with no nails.

Here's an occupational-safety video, as cool and stylish as such videos tend to be, explaining this:

The best thing to do is stay in the vehicle and let the electricity pass around you; the metal frame of a truck is way more conductive than a human, and you're probably sitting on an insulating seat anyway.

If you're in a sparks-and-fire situation best viewed from a considerable distance...

...though, then hopping out of the vehicle so that you don't touch the vehicle and the ground at the same time, and then pogo-hopping away, is the best chance you have to avoid becoming a very crispy critter. (If you don't want to see the severely charred body of a fork-lift operator who lifted his fork into power lines, don't click here.)

Tiny mincing steps can work about as well as pogo-hops, and may be safer in construction-site terrain. The idea is to get away without falling on your face and enjoying the large potential difference that now exists between your knees and your nose.

Even an actual earth stake may become less and less effective as a current sink if a lot of power passes through it for long enough, because that'll heat the area and boil out the water that makes the ground usefully conductive. The same applies to vehicles that are shorting power lines to ground; as the arcing and burning progresses, the area under the vehicle gets drier and less conductive, and the danger zone expands. Usually the power's cut off pretty quickly, but not always.

(For this reason, dry sand and most kinds of desert-dry ground are a bad place to hammer in an earth stake. Since you'll find water just about anywhere if you dig deep enough - this is the Great Secret of Dowsing - you can get around this problem by using a really long earth stake, provided you have some way to pound it into the ground. Hammering in an ordinary earth stake and pouring water around it will work just fine... until the water drains or evaporates.)


Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

Snake-oil by phone

A reader (and commenter) writes:

I realize you're probably sick to death of hearing about PFC scams, but this might amuse you anyway: I just got a phone call from a heavily-accented call-center voice purporting to be part of an energy-saving campaign by my electricity provider, Hydro-Quebec. They promised to send me a gadget which I would plug into any outlet and which would reduce my electricity consumption 30-40%.

(Initially I thought it might be a Kill-A-Watt or similar, which I would actually use, or could if my ancient inefficient appliances didn't belong to my landlord.)

When I asked how it worked, they claimed it contained "three special capacitors" and that it reduced some sort of ill-defined stray currents in my wires, and that it would reduce what was read on my electricity meter by the above 30-40%. Initially they gave the impression they were going to just send it to me, which I would have gleefully accepted so that I could dissect it and demonstrate its non-function. But it transpired that they were actually offering me a "great deal" and a "once in a lifetime offer" - yes, those are the words they used - of 50% off on its $400 price.

Once it was clear I wasn't going to get a piece of hardware for skewering, I suddenly found I had better things to do. I called Hydro-Quebec and they know there are people doing this, they had a security department number to hand (which referred me to the Canadian Anti-Fraud Office, which isn't open), but I was kind of surprised to get it at my home number.

Anne

Yes, I am just a little tired of bogus power savers, having written about them here, here, here and here on Dan's Data, and here, here, here, here and here on this blog.

But it bears re-re-re-repeating, here and elsewhere, because people are still selling these things (and removing all doubt in the comments of relevant blog posts...), and innocent people are still buying them. The more frequently this message is repeated, the more of a public service it does:

Magic power savers that're somehow meant to substantially reduce your household (or small business) electricity bill by hazily-described means involving capacitors, power factor or even stranger alleged technology are, without exception, scams. Power factor is a real thing and so is power factor correction, but household and small-business electricity consumers are almost never billed by power factor - spinning-disc electricity meters can't even measure it - and magic one-size-fits-all power-factor-correcting gizmoes don't actually even do what they're supposed to. The components inside these things aren't necessarily even connected. So even if you were billed by power factor, these gadgets would not improve it.

I have, to date, not had the pleasure of some guy with an Indian accent trying to sell me a magic power saver over the phone. Indian dudes ringing the doorbell and trying to get me to change my electricity supplier, yes; phone solicitations for power savers, no.

(The door-to-door guys are probably having a pretty bad time. I presume someone's making out like a bandit hiring Indian kids for a "working holiday" in beautiful Australia, then leaving the unfortunate workers stuck in yet another of those godforsaken semi-scammish door-to-door sales jobs that only pay by commission and have all sorts of outrageous requirements designed to soak up what money the poor bastards do manage to make. The door-to-door electricity guys, here in Australia where the power industry is still well enough regulated that there are no real "scam" providers as far as I know, are kind of like the Kirby vacuum or Cutco knife salespeople, selling a legitimate, if overpriced, product in an unpleasant way. They are, at least, not selling white-van loudspeakers, or fake health insurance to grandmas.)

My household has, however, been enjoying the attentions of another breed of Indian-accent phone-scammers. These guys, invariably identifiable thanks to the distinctive autodialer pause when you pick up the phone, were calling us a couple of times a week, though I think they've been quiet for a little while now. We may have finally persuaded them to stop, or perhaps they got busted. Or, more plausibly, they've submerged and departed for a while to avoid being busted.

Aaaaanyway, these guys usually say they're from Microsoft or something, and tell you there's something terribly wrong with your computer, and you need to go to their Web site and install some malware to fix the problem.

Anne (my Anne, not the Anne at the top of this post) has frequently asked these callers why they do not seek honest employment. The next time I pick up a call from them, I think I'll pretend to be racist.

"Is there, do you know, a single honest man anywhere in India? Clearly the British need to return and take you naughty little children firmly in hand once again. You silly little dusky monkeys, bless your souls, simply cannot grasp the white man's honour, can you? It's really not your fault; you simply cannot tell right from wrong. We blame ourselves, you know. It was foolish of us to trust you, with your tiny, adorable brains, to govern yourselves."

(Suggested background music.)

Just wasting a telephone scammer's time is small potatoes. We must aim, instead, to induce incoherent rage.

Button batteries: Threat or menace?

A reader writes:

The Register had this story; it paraphrases a study from Pediatrics but includes this paragraph:

The incidents are no laughing matter, as a swallowed button cell can generate sufficient current to burn a hole in a child's oesophagus, from the inside, without the child displaying any obvious symptoms. Acid can also injure. Even batteries that appear depleted, inasmuch as they can no longer power electrical devices, can inflict these injuries.

Is it just me, or is the claim that a mostly-depleted button cell can "burn a hole in a child's esophagus" via electrical current a complete and obvious impossibility? By leaking strongly acidic or basic electrolyte I can buy, but by electrical action?

Charles

In brief: Yes, the problem here is burning, and it can be very serious. But it's not electrical burning, it's chemical burning, specifically as a result of electrolysis of tissue fluids. And if a battery makes it to the stomach, the swallower is likely to be OK; it's only if it lodges in the oesophagus that big trouble is likely to result.

Well, that's what I learned in the course of writing the following Wall O' Text, anyway.

("I would have written a shorter letter, but I did not have the time.")

Whenever you find yourself wondering about some oddball medical news, you should proceed directly to PubMed.

(This is particularly important if you got the news from a newspaper or TV show, many of which can be relied upon to get almost all science news solidly wrong. Mass-media science reporting is sometimes good, but it's very often terrible, for surprisingly complex reasons. Whenever I hear some interesting-sounding science report on TV news, I try to remember the first five seconds of the report and expunge the rest of it from my consciousness, so I can look up what, if anything, has really been discovered, without wasting any neuron-connections on what some attractive ignoramus thinks is going on. See also, jazzed-up, dumbed-down reality shows, some of which make a real effort to get things right, and some of which don't.)

PubMed lets you search the Medline, and some other, medical research databases. You'll generally only get the abstract of each paper (and not even that, for some), and you're not tremendously likely to be able to find the whole paper for free anywhere (a situation which should change, and actually may). But a quick PubMed search will nonetheless give you a rough idea of the state of research on a subject.

If you lean on PubMed for evidence when you're having an argument with someone, the two of you are likely to end up playing what I call Duelling Abstracts, in which neither of you knows how good any of the research you're citing is, so you both just end up Bullshitting for Victory. All research is not of the same quality, and PubMed will cheerfully present you with numerous papers in support of almost any nutty idea you like. (This is largely because Medline indexes many dodgy journals along with the respectable ones.)

Assuming you're not using the science for support, rather than illumination, you need to see how well a given piece of research was done, and how often it's been reproduced by other researchers, before you should cite it in a serious discussion. (At least few bad papers are the result of outright fraud. Unfortunately, though, a paper often has to be blatantly and quite famously fraudulent before it'll actually be withdrawn, though this situation is improving.)

But if you're just trying to see whether there's any research on, say, kids swallowing batteries, and you don't need more detail than you get from paper abstracts or letters written to medical journals (PubMed doesn't only index research papers), a couple of minutes on PubMed is all you need.

I was surprised to discover that there's actually quite a bit of literature on the subject of kids eating small batteries. I suppose it's the result of more and more consumer items that run from these tiny batteries. In 1980 you might have had a lithium coin or an alkaline LR44 in your calculator or wristwatch, or a silver-oxide cell if you were fancy, or a zinc-air battery in your hearing aid and maybe a mercury battery in your camera. But plenty of people didn't have one button cell in their house.

Nowadays, small remote controls, key-ring flashlights, laser pointers and umpteen other glowing tchotchkes run from miniature batteries, and it's easy to get the batteries out of most of these items. The only other thing you need to guarantee many tiny-battery-ingestion events is firm instruction from a parent that children must most emphatically not eat said batteries.

However it happens, kids are eating batteries, and the results can be quite serious.

I initially thought some danger might be posed by lithium batteries, which really do contain metallic lithium...

...which isn't as excitable as its relatives further down the leftmost column of the Periodic Table, but which is still not something you want running around loose in your stomach. Lithium salts: Mood stabiliser. Metallic lithium: Mood ruiner.

In theory, stomach acid could eat through the casing of a battery, but in practice this doesn't seem to happen. Especially not with lithium cells, which are deliberately made very resistant to corrosion specifically to stop them from starting fires all over the place. The same goes for pretty much every other tiny battery; I don't know which of them have stainless-steel casings, but it seems they can be expected to pass through the gastrointestinal system pretty much intact, even if they do some damage on the way.

The mechanism for said damage does seem to be electrical, but not directly. Even a brand new button cell doesn't have a lot of power to deliver, and the harder you load a battery the less capacity you'll get, but swallowing a battery will give it a quite nice low-resistance pathway from one terminal to the other, and button cells all have terminals separated by only a millimetre or two. This means something close to the battery's full short-circuit current could flow through a quite small amount of tissue. The relatively large circumference of a coin cell will spread out the affected area a bit, unless the battery lodges in such a way that only part of its circumference has a good contact.

To see how much current that actually is, I threw together a battery-torturing apparatus...

Battery-torturing apparatus

...in which the twenty-amp current range of a multimeter, with about one ohm of resistance including the wires, stood in for the conductive lining of a human gut. I think one ohm is a pretty good figure to go with, here; human tissue is often not very conductive at all (put multimeter probes next to each other on your tongue and you can get a surprisingly high reading; more invasive test techniques are discouraged), but I think the internal mucous membranes, plus stomach acid or one or another salt, are both pretty conductive and pretty easy to damage.

My first victim was a tiny LR754 alkaline button cell, 7.9 by 5.4 millimetres in size, which had been sitting in my miscellaneous-battery drawer for a while but still had an open-circuit voltage above 1.5 volts. At the moment when I clicked the magnetic contacts onto the cell it produced more than 0.2 amps, but this fell to 0.1 amps after 30 seconds, 0.07 after a minute, and so on down the line until it was 0.01 amps at five minutes.

(Because I was using the super-low-resistance 20-amp range on the meter, the lowest current I could measure was 0.01 amps, and I wouldn't bet my life on the meter's accuracy either.)

Next I tried a CR2016 lithium coin cell, 20mm in diameter and 1.6mm thick. These cells are commonly used in Photon-type key-ring flashlights; red key-ring lights can run from one double-thickness CR2032, but blue, green and white LEDs need more voltage and so run from a series stack of two 2016s.

(Modern computer motherboards usually have a 20-series coin cell as their BIOS-setting backup battery. It'll probably be a CR2032, but in a pinch you can substitute a 2025 or 2016; the thinner cells should still fit the contacts. Don't stack thinner cells to fill the holder, though!)

The 2016's initial open-circuit voltage was 3.25V, but it managed less than 0.01 amps from the outset.

I thought I might have picked a defective or very old CR2016, but who cares, if the ceiling performance of shorted lithium coins isn't high enough to be a worry anyway? So I next tried to establish where that ceiling is by testing a beefy (by coin-cell standards) CR2430 (24mm wide, 3mm thick), which had also been on the shelf for rather a while and only started at 3.16 volts open-circuit, but which still should be able to easily beat any of the more common 2016s or 2032s.

The 2430's initial current was up around half an amp, but that lasted less than a second. It managed 0.16 amps after 15 seconds, 0.12 amps after a minute, 0.09 after two minutes, and kept going strongly (again, by coin-cell standards); it still managed 0.08 amps after four minutes, 0.06 after seven minutes, and was still managing 0.03A after thirty minutes, which was when I unshackled the prisoner from the wall and consigned him to eternity in the rubbish bin.

OK, so this cell managed to deliver something in the neighbourhood of a tenth of an amp for at least a few consecutive minutes. Voltage equals current times resistance, so if the current is 0.1 amps and the resistance is one ohm, there must be only 0.1V across the battery. (Voltage sag is normal in overloaded batteries.) Power equals voltage times current; 0.1 volts times 0.1 amps gives a miserable ten milliwatts of power, which even if it were concentrated in one small spot probably wouldn't, I think, directly singe even a baby's oesophagus.

My last victim was an alkaline LR44. I think this is the button battery most likely to end up inside a child, because it's both conveniently pill-shaped and very widely used. The one I chose started out at 1.57 volts open-circuit, and initially managed to deliver more than 0.3 amps into the short circuit. This, again, fell very rapidly, to 0.23 amps at 15 seconds, 0.21 at 30 seconds, 0.18 after a minute, and so on. At five minutes it was 0.12 amps, and just before ten minutes it suddenly fell from 0.07 amps to only 0.01, perhaps because of some internal failure caused by the short.

(The LR44 didn't get hot or leak, though. Modern batteries are extraordinarily good at not leaking, and only partly because we now use a lot of alkalines instead of carbon-zinc cells which corroded away their zinc casing as part of their normal operation. Un-leaking batteries are one of those things, like un-popping tyres, that now give so little trouble that people fail to even notice them any more.)

OK, let's suppose we've got a very beefy LR44 that manages to deliver 0.3 amps into one ohm for a significant amount of time. V equals IR, once again, I is 0.3, R is 1, therefore V is 0.3V, and V times I is a pathetic 0.09 watts. Again, this doesn't seem to me to be very dangerous.

And the medical literature mostly agrees.

If a button battery lodges in the oesophagus then you have a problem. A neck-lodged battery can cause a tracheo-oesophageal fistula (a hole between the trachea and the oesophagus); one did in this unfortunate one-year-old, who recovered, and in this toddler, who didn't.

One of the couple of kids who apparently managed to eat an LED throwie escaped without drama. This kid for some reason ate multiple magnets and batteries, but only the magnets then caused trouble.

Interestingly, there's a two-page guide to "Management of children who have swallowed button batteries", which was published in 1986 in Archives of Disease in Childhood, in PDF format here. It agrees with the newer papers that it's lodgement in the oesophagus that's the problem, but says thin lithium coin cells don't seem prone to lodge at all. And it also speculates that an increase in pH (an increase in alkalinity around the battery's anode) is what causes tissue burns, not simple electrical heating or leaking chemicals from inside the battery.

A swallowed battery is essentially electrolysing water wherever it comes to rest. That'll produce hydrogen bubbles on one terminal and oxygen bubbles on the other, but the salts that make saliva, gastric juices and tissue conductive will electrolyse too. Sodium chloride in water, or hydrochloric acid from the stomach, could give you chlorine bubbles along with the others, which would be bad news. Perhaps it's that, along with mechanical damage from the child trying to swallow the battery or cough it up, that causes fistulas and their life-threatening consequences.

Given the feeble numbers I got by short-circuiting miniature batteries, I agree that there really doesn't seem to be any electrical burning going on there. You'd just need more watts per conductive length than 1.5V and 3V miniature batteries can deliver. A twelve-volt A23 battery might do it; A23s have a stack of tiny button cells inside them, and used to be ubiquitous in small radio transmitters like car central-locking key-fobs and wireless doorbells, but are now being replaced by lithium coins. I bet a standard rectangular nine-volt battery could do it too, in the unlikely event that even a full-grown adult, let alone a child, somehow managed to ram one down their throat. There are rechargeable button cells as well, which like other rechargeables have a lot more current capacity than non-rechargeables of the same size, but they're rare enough that no child may ever actually have swallowed one.

There are various other individual case reports, ranging from the benign to the fatal, in the face of which one should remember that surely for every kid who ends up in hospital for battery-eating there must be a few who ate and later excreted a battery without any adult noticing. Or, at least, without any adult noticing until they changed that nappy.

Saving the best for last, here we have "an analysis of 8648 cases", the full text of which is available for free. The authors conclude, and also say in this slightly later paper (also online for free), that the severity of battery-swallowing injuries is getting worse, because of proliferation of 20mm-plus coin cells, which (in contradiction of the 1986 management guide) now seem to be the most dangerous. Misdiagnosis seems to be a major part of the problem, though, which shouldn't be too hard to fix since batteries show up loud and clear on an X-ray. Oh, and kids do manage to swallow AAA and AA batteries too; more than 5% of the 8648 cases involved "cylindrical cells".

These authors also say it's alkalinity - formation of hydroxide ions in tissue fluids next to one terminal of the battery - that "is now appreciated as the most important mechanism" in batteries damaging flesh.

So yes, swallowed batteries can "burn" the swallower, but chemically, not via resistive heating, which barely happens at all because these batteries can't deliver much power.

In the absence of complications like swallowed magnets, there only seems to be a danger if the battery lodges in the oesophagus. But 20mm and larger lithium coin cells are a good size to do exactly that, and if one does, there appears to be a good chance of very bad results. The authors of those two meta-analyses says there's a 12.6% chance that a child younger than six swallows a 20mm-plus coin cell will "experience serious complications or death", but they base that primarily on the records of the US National Poison Data System and National Battery Ingestion Hotline (who knew?), which of course don't get to hear about battery-consumption that doesn't cause any problems and passes unnoticed.

Still, in the million-item list of things for parents of young children to freak out about, this doesn't seem like a silly one. I think parents could do worse than scan their house for remote controls, kitchen scales, toys and so on that have small and easily-removed batteries.


Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

They called it "big iron" for a reason

A reader writes:

After reading "Welcome to my museum", I'm now fascinated by the power supply equipment used on early Cray supercomputers. Can you explain more about the Motor-Generator Unit, and where you found the information? There doesn't seem to be much literature about it on the interwebs.

Colin

Cray Motor-Generator Unit

I found out about the extraordinary supporting equipment the Cray-1 needed in the "Cray-1 Computer Systems M Series Site Planning Reference Manual HR-0065", dated April 1983, which you can get in PDF format here.

I think I originally found that manual in the Bitsavers PDF Document Archive, here. They've got a bunch of other old Cray documentation in this directory, including document HR-0031, the manual for the optional Cray-1/X-MP Solid-State Storage Device (SSD).

You could very easily mistake that device for a modern SSD, except for minor details like how it had a maximum capacity of 256 megabytes, and was larger and heavier than some cows. I'm not sure quite how much larger and heavier, though, because that's covered by document HR-0025, which unfortunately doesn't seem to be online anywhere.

(The top-spec 256Mb version of the SSD did have a 1250-megabyte-per-second transfer rate, though, more than double the speed of the fastest PC SSDs as I write this. The Cray SSD's main purpose was apparently to serve as a fast buffer between the supercomputer's main memory and its relatively slow storage. Traditional supercomputers, as I've written before, were always more about I/O bandwidth than sheer computational power.)

The Site Planning Reference Manual is sort of a tour rider for a computer. Van Halen's famous rider had that thing about brown M&Ms in it as a test to see whether people at the venue had read the rider, and were thus aware that they needed to provide not only selected colours of confectionery, but also a strong enough stage and a big enough power supply. I presume the Site Planning Manual has in it somewhere a requirement that there be an orange bunny rabbit painted on one corner of the raised flooring.

(At this point I have to mention Iggy Pop's rider as well, not because it's at all relevant to the current discussion, but because it's very funny.)

I think the deal with the Motor-Generator Unit was that the Cray 1 needed not just enormous amounts of power (over a hundred kilowatts!), but also very stable power. So it ran from a huge electric generator connected directly to a huge electric motor, the motor running from dirty grid power and the generator, in turn, feeding the computer's own multi-voltage PSU. The Cray 1 itself weighed a mere 2.4 tonnes, but all this support stuff added several more tonnes.

(My copy of the HR-0065 manual is over on dansdata.com, hosted by m'verygoodfriends at SecureWebs, who in their continuing laudable attempts to wall off IP ranges corresponding to the cesspits of the Internet occasionally accidentally block traffic from some innocent sources, like an Australian ISP or two. If you can't get the file there, you can of course go to Bitsavers instead, or try this version, via Coral. You can use Coral to browse the whole of Dan's Data if SecureWebs isn't playing ball, though it may be a few hours out of date.)

You don't want to meet Michael Palin there

A reader writes:

Why do nuclear power stations (and other power stations, for that matter) have cooling towers in that weird half-hourglass shape?

I presume the guys who built them knew what they were doing, but what did they know that I don't?

Ian

Cooling tower

I pledge to eventually answer your question, Ian, but first I'm going to rabbit on interminably about power stations.

The cooling tower has become emblematic of nuclear power stations, and the white "smoke" drifting from the top of them is a source of vague nervousness for a lot of people.

But, as you say, other kinds of power stations have cooling towers too. I live less than an hour's drive from Lithgow and the Mount Piper and Wallerawang Power Stations, able to produce 3.4 gigawatts of coal-fired electricity between them; Mount Piper has two cooling towers, Wallerawang has one. The "smoke" that comes out of these towers is actually just clouds of tiny water droplets.

(Once again, if you can see it, it's not "water vapour". Clouds, and the visible "steam" squirting out of a kettle or a steam locomotive, are liquid water droplets with a ceiling temperature of 100°C at sea-level air pressure. It's possible for actual invisible-vapour steam to be swirled in with condensed droplets as it mixes more or less chaotically with the outside air, but "pure" steam is invisible, and has no ceiling temperature. Put your hand in the visible portion of the steam coming out of the side of a locomotive and you may get scalded, but putting your hand in the invisible jet close to where it's exiting may flense the flesh from your bones.)

Power stations need cooling towers, or some other heat-sink like water from a convenient river, because they are heat engines. Heat engines, as I've written before, become more and more effective as the temperature difference between their "hot end" and their "cold end" increases.

A heat-engine that makes this fact obvious is the now-quite-standardised sort of "coffee cup" Stirling engine...

...which stands on a wide circular displacer-piston cylinder and can run on the heat from a cup of coffee or tea, or backwards on a cup of ice-water. I've got one that runs like this, but really low-friction versions of the design can run on the heat from a human hand, if the ambient temperature is cool.

(You can pay quite a lot of money for a jewel-like Stirling engine {or, more interestingly, a kit to build one}, but this eBay dealer, in addition to being called "Stirlingeezer" which ought to be a reason to buy from him all by itself, sells quite beautiful engines and kits that are guaranteed to run from hand-heat. If enough people buy stuff via the above affiliate link to Stirlingeezer, I shall soon be able to afford one of his engines!)

(Oh, and if you're short of money, you can get a Stirling kit for $US30 delivered, or conceivably less if you get lucky with your bids, from this guy in China.)

Conventional power stations, whether fired by coal, combustible gas of one kind or another, or a nuclear reactor, make their electricity by turning a turbine connected to a generator. Gas-fired stations can do this directly with a gas turbine, which is essentially a jet engine tuned for shaft-turning power, rather than thrust. Coal and nuclear stations make electricity less directly, by using the heat of combustion or nuclear fission to boil water and run a steam turbine.

(I think there are also gas power stations that use steam turbines. There are definitely gas power stations that burn the gas in one turbine, and then run another, different turbine from the hot exhaust of the first one.)

Anyway, that's the hot end. A well-designed heat engine will try to get its cold end as distant in temperature from the hot end as is practically possible. The ratio between the two temperatures, expressed in Kelvin (or any other temperature scale, as long as it starts at absolute zero), determines the maximum possible efficiency of a heat engine.

Sometimes "the cold end" is synonymous with "the exhaust temperature"; that's how it works for internal-combustion piston vehicle engines, and steam engines too. A classic example of the latter is the triple-expansion compound steam engine. This has one small piston for the fresh, hot, high-pressure steam right out of the boiler. The medium-heat, medium-pressure exhaust from this first piston powers a medium-sized piston, and the low-heat, low-pressure exhaust from that piston in turn runs one or more even bigger pistons. (This can theoretically be extended to even more stages, but in practice quadruple-expansion was about as far as anyone could get before the gain in efficiency wasn't worth the extra complexity and friction.)

Steam-turbine power stations, on the other hand, may emit exhaust gases from the burning of fossil fuels, but the system that makes the actual electricity is a closed, Rankine-cycle steam/water circuit. The burning fuel or fissioning atoms heat cool water to steam, the steam turns a turbine or three, and the turbine exhaust then goes to some sort of cooling device, generally a heat exchanger, that dumps the final unusable portion of the water's heat somewhere.

This "somewhere" can be a separate water supply, either a river, large lake or sea, or it can be evaporating water in a cooling tower. Once the heat exchanger has cooled the closed system's water in whichever way, that water is pumped into the boiler again, and the cycle continues.

You might wonder why you need to dump heat from the turbine exhaust, when you're only going to heat the water up again in the boiler. There are two practical reasons for this.

The first reason is that the exhaust from a power turbine is almost all still water vapour, because, in brief, turbines made to run on a flow of hot gas do not like it if the gas condenses to liquid inside them.

The second reason is that the pump that returns the water to the boiler has the opposite preference; it only works with liquid water. It would be possible to use a gas pump instead and make a system in which the working fluid is always vapour, but the energy needed to run a gas pump against pressure from the boiler is high, while the energy needed to run a water pump is trivial (by power-station standards), on account of the incompressibility of the water.

The upshot of all this is that standard 20th-century power stations are pretty miserably inefficient. Today, there's much more effort being made to reduce the heat wasted, by for instance transferring some of the heat of the turbine exhaust to the water feed between the pump and the boiler, or by using some of the waste heat to keep nearby buildings warm ("cogeneration"). These sorts of measures can only go so far, though, so cooling towers of one shape or another will continue to be built.

Which, finally, brings us back to the classic cooling-tower shape.

Cooling towers actually come in all shapes and sizes; large air conditioners, for instance, often have evaporative coolers for their chillers, but those coolers don't look anything like a power-station cooling tower.

Power-station coolers have to have very large capacity, so they inescapably have to be very large. Power-station coolers also have to provide a decent convective "stack effect", also known as "draught" (or "draft", in the less-demented American spelling). But, importantly, power-station coolers don't really need to be able to hold up much more than their own weight, plus any remotely plausible wind loads or shifts of their foundations.

The classic curvy cooling-tower shape fits all of these requirements. In engineering terms, because cooling towers don't need to hold up an interior full of offices, they can be built as a "thin-shell structure". You could build a cooling tower out of giant Great-Pyramid stone blocks if you wanted to, but a surprisingly thin reinforced-concrete shell, built in layers from bottom to top (not unlike the way 3D printers work), is the usual solution. And the builders almost never balls it up.

Objects of this shape are called "hyperboloid structures"; they're strong for their weight and so have been used for all sorts of masts and towers and, sometimes, ordinary buildings too, and they're particularly suited for use as cooling towers. The large area at the bottom of the hyperboloid gives lots of room for evaporation, the "waist" accelerates the gas mixture (I think because of the venturi effect), and then the widening opening at the top encourages turbulent mixing with the ambient air. (Air gets into the tower in the first place via an open latticework section around the base.)

(Oh, and I just have to take a moment, here: Segmentally Constructed Prestressed Concrete Hyperboloid Cooling Tower! Segmentally Constructed Prestressed Concrete Hyperboloid Cooling Tower! Segmentally Constructed Prestressed Concrete Hyperboloid Cooling Tower! Thank you.)

The final question that occurs to me in this area is why cooling towers are hyperboloids, but factory chimneys are cylindrical (or close to it - they often taper a bit toward the top).

This is because the cooling tower wants to move a vast amount of low-pressure air. The evaporating warm water at the bottom of the tower produces a steam/air/water mixture that isn't much warmer, and thus less dense, than the ambient air, so it has little buoyancy compared with the ambient air, won't move terribly fast, and so has to pass through a really wide pipe. Factory chimneys, on the other hand, are moving a much smaller volume of much warmer gas, usually combustion-product "flue gas". This is usually quite a lot hotter than ambient, so it rather wants to go up a chimney and doesn't need a wide one; you just need a nice long chimney, both to get a strong stack effect and to discharge the gas as high up as possible, to spread the pollution by dilution, as it were.

(Incidentally, The Secret Life of Machines addresses the stack effect in episode five, on central heating. And while I'm on the subject, the extraordinary documentary Fred Dibnah, Steeplejack features the titular working-class hero climbing hundreds of feet up a brick chimney and then perching on scaffolding that looks as if it were assembled by blind drunkards and knocking the chimney down by bashing bricks, one by one, into the flue. It has to be seen to be believed.)


Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

The music goes round and round and comes out backwards

A reader writes:

Sometimes when I plug in my headphones it seems as if I'm not receiving any vocals. Its still stereo, but I find that the headphone jack isn't completely in. What's going on here? And why does it work so effectively at removing vocals?

Simon

The quick answer: You're hearing the two stereo channels mixed, with one of them out of phase with the other.

I can't for the life of me figure out how this happened, though. In the interminable rambling below I talk about a couple of other crossed connections that can, and often do, happen, but unless there's a bit of wire stuck in the headphone socket or some other such oddity, I don't know how you could have the exact symptoms you report. Unless, of course, what you think you're hearing isn't what's actually happening, which is eminently possible since the ear is as easy to fool as the eye.

Anyway, mixing one stereo channel with an opposite-phase version of the other channel means that any component of the musical mix which is essentially monophonic - in the middle of the stereo "soundstage", the same on both channels - will be cancelled out.

Singing in popular music is, usually, pretty much in mono in the middle of the stereo mix. So mixing one side with a phase-flipped version of the other side will cancel out said singing; all you'll hear of the singer is any stereo reverb or difference in volume between the two sides (a.k.a. panning).

This technique, called Out Of Phase Stereo or OOPS, is used in this simplest form by old and/or cheap karaoke machines that let you "mute" the vocals on normal music, so you don't need a special vocal-less karaoke version of every song.

Simple OOPS doesn't work very well, because vocals are seldom exactly in mono (they usually have some stereo reverb, for instance), and if any other component of the mix - drums, bass, whatever - is also mono, then that'll be muted too. Smarter OOPS vocal-muting tries to identify and mute only the vocals, based on the pitch and possibly even the timbre of the sound.

This weirdness can come about because headphone plugs use TRS (Tip, Ring, Sleeve) connectors. TRS connectors come in a variety of sizes - the big old-fashioned 6.35mm (quarter-inch), the ubiquitous modern 3.5mm (eighth-inch), and the usually unnecessary and irritating 2.5mm (3/32 or 1/10 inch, depending on who you ask). All three-contact audio TRS connectors are, or should be, wired the same way; the tip of the plug is left channel, the ring is right channel, and the sleeve at the base of the plug is a shared ground.

(This sort of cylindrical plug connector should only be called "TRS" if it has these three contacts. Mono-audio cables with the same sort of plug, like for instance guitar leads, omit the ring contact and should therefore be called just "TS" connectors. Connectors with two ring contacts, as for instance used for stereo headsets with a microphone, should be called "TRRS". Sometimes you'll see any plug of this basic form called a "TRS" plug, though, regardless of how many contacts it actually has.)

Most headphones today have a 3.5mm plug; fancier ones...

Sennheiser plug

...come with a 6.35mm adapter for it, too.

Some headphones mix it up a bit. One of these Sennheisers has a simple 3.5mm TRS plug on both ends of its cable, so you can very easily and cheaply replace the cable if it's damaged...

Sennheiser cable plugs

...but the other has a 3.5mm TRS on one end of its cable, and at the other end the cable splits into a pair of 2.5mm TS plugs, one for each side of the headphones.

If a TRS plug isn't fully inserted, contacts on the plug can touch the wrong contacts in the socket.

(This characteristic makes this shape of plug a bad fit for many applications. I once bodged up a two-voltage power-supply connection for an external SCSI drive box for, of course, my Amiga, using a 6.35mm TRS plug and socket. I avoided the dangers of connecting one voltage to the other's contact and the other voltage to the ground contact by only connecting or disconnecting the power supply when everything was turned off. Or, at least, connecting or disconnecting it really fast.)

A partially-inserted TRS plug could, for instance, leave the tip contact on the plug touching the ring contact of the socket, and the plug's ring contact not touching anything, and the sleeve of the plug still touching the sleeve of the socket, because the sleeve is much longer than the other two contacts. This sort of mis-connection will give you the signal meant for your right ear in your left ear, and no sound from the right side of the headphones.

(The sleeve of the plug is connected to the braided or foil shield of the cable, and any or all metalwork on the plug that is not the tip or ring contact will also be connected to the shield - it's all one big sleeve contact, basically. TRS sockets almost always work the same way; the socket has small tip and ring contacts, but the rest of the socket's metal is all sleeve. This makes it very easy for the sleeve of plug and socket to remain connected when the plug isn't all the way in, and if the plug's a long way out of the socket it also makes it pretty easy for the plug's ring contact to touch the socket sleeve contact.)

I encourage readers, by the way, to try this out yourselves; it's pretty much impossible to hurt your headphones or anything you plug them into by only plugging them in half-way. So do that, especially if you find my interminable blather confusing, or just want to see if you can create Simon's symptoms for yourself.

Another mis-connection could have the plug-tip touching the socket-ring, and plug-ring touching socket-sleeve. Now you'll hear the signal meant for the right side through both ears, but it'll sound weird, because it's out of phase, as mentioned above.

This is because the left and right "drivers" of the headphones (the electromagnetic transducers that actually make the sound) are, with this mis-connection, now wired in series, with the wire going "out" of the left driver that's meant to connect directly to the sleeve contact instead only being able to connect to the sleeve through the right driver and the plug's ring contact, thereby feeding the right driver "backwards".

This causes the right side to be out of phase - when the left driver is moving toward your head, the right one should be too, but now its phase is inverted and it's moving away.

There are two reasons why I'm rabbiting on about this stuff at such outrageous length. The first is that basic audio cabling like this is something that almost everybody has to deal with, and it pays to know what connects to what even if you don't intend to be soldering up any cables of your own - though basic soldering is easy to learn, cheap, and can save you quite a bit of money.

(Just yesterday, I turned a couple of not-that-cheap Apple laptop power supplies, one electrically dead and the other with a fractured and fiendish-to-repair MagSafe plug, into one working power supply with an extra-long cable. Even the dodgiest off-brand MagSafe power supplies are about $US20; a genuine Apple one is $79. With basic soldering skills and equipment, this sort of thing is a literal five-minute job.)

The second reason for this ridiculously large post is that phase problems are actually very common in home audio, and not only among people who fix their own headphones and get one set of Profanity-Allowance-consuming minuscule wires backwards.

People have been creating phase problems ever since the invention of stereo, occasionally by mis-connecting a turntable cartridge, but usually by wiring one of their stereo speakers the right way around (red terminal on the amplifier to red terminal on the speaker, and black to black) and the other the wrong way (red to black, black to red). In this case, each speaker actually is playing the signal that it should be, but one is phase-inverted.

(It doesn't really matter whether you've connected red-to-red or the other way around, as long as both speakers are the same. In theory, having both out of phase with the way they should be, but in phase with each other, could cause an audible difference, but in practice it's only detectable by golden-eared audiophiles who see no need for tiresome things like blinded tests.)

If you've got two working ears, you definitely can hear when stereo has one side out of phase. It's hard to describe, though; it's sort of like having a head cold that's blocked one of your Eustachian tubes but not the other, or how things sound when an air-pressure change has popped only one of your ears. Here's a page that explains this, with nifty audio samples including one (MP3 link) that should sound mono in the first half and out-of-phase pseudo-stereo in the second half.

Out-of-phase audio sounds different on headphones and speakers, because of the basic differences between the two devices. Headphones deliver pretty much pure left-signal to your left ear and right-signal to your right, but each of your ears hears both members of a stereo speaker pair, plus umpteen reflections and resonances from the room you're in.

For this reason, if you're listening to stereo speakers with one side out of phase, there will be strangely little bass, because low-frequency sound has a long enough wavelength that the out-of-phase speakers can mix their sound even if they're separated by a few metres. Higher-pitched centre-mixed components of the music won't cancel as much, though.

Just to make things even more complicated, sometimes it's good to reverse the phase of a subwoofer or surround speakers, to compensate for subwoofer location or the distance of the surround speakers. There's often a hardware switch on a subwoofer or a configuration option on a surround receiver that'll let you do this, or of course you can just switch the wires around or make a crossover RCA cable.

There are also some stereo recordings on which phase reversal is undetectable, because the two channels share nothing at all. Many early stereo rock tracks are like this, and are pretty much intolerable to listen to with headphones because the stereo mix puts each instrument entirely on the left or right channel. Ringo and Paul on the left, John and George on the right. Nobody minded this very much at the time, because almost everyone heard this music in the mono mix, but to make these tracks listenable with headphones you need a fancy headphone amplifier, or music-playing software, that has a "crossfeed" control, to deliberately mix some right into the left and some left into the right.

Out-of-phase mono - the same signal on both sides, but one way round on the left and the other way round on the right - kind of sounds like stereo, because you genuinely are hearing something different on each side. So what I think you, Simon, are hearing from your partially-connected headphones is a mixture of left and right, with one side's waveform inverted, the resultant mono signal being heard one way round on the left side and the other way around on the right. I just can't figure out how you could electro-mechanically get this to happen by only partially plugging in the headphones. I presume there's one contact on plug or socket that's touching two contacts on socket or plug, but I don't know which.

It is, again, entirely possible that you're not perceiving what's going on correctly; psychoacoustic effects can be powerful. But perhaps I'm just insufficiently imaginative. Any ideas (or experiment reports!), commenters?

One LED, two LED, red LED, blue LED

A reader writes:

Myself and a friend were just reading Big Clive's "Hack your solar garden lights", and we are unsure how he came to those amp readings and the conclusion that two LEDs use less amps than one.

LED brightness comparison

I am assuming we are just missing something, could you please enlighten us?

Daniel

To oversimplify, two LEDs in series have more resistance, so less current flows. But halving the current passing through an LED doesn't necessarily halve its brightness. Standard high-brightness 5mm LEDs generally have a 20-milliamp current draw on the spec sheet, but will glow from much less, and may be considerably more efficient at small currents.

The reason why this is an oversimplification is that LEDs, unlike incandescent-filament lamps, aren't just a relatively simple resistive device.

(And the "relatively" is in that sentence because not even tungsten-filament bulbs are completely straightforward. They have, for instance, a much lower resistance when cold than when operating. And reducing the power of a filament bulb will generally give you a reduction in apparent brightness that's greater than the reduction in power, because the filament will be cooler and more of its output will be down in the invisible infrared. LEDs, in contrast, only know how to make one colour, even when they're only barely creating a tiny spark of light. This is the case for white LEDs too, because to date all of those are actually blue LEDs with a phosphor coating that turns some of the blue light into other colours.)

Instead of being resistors, Light Emitting Diodes are, yes, diodes, with a constant voltage drop across them at a given temperature. But when they're lit they get warmer, causing them to pass more current and glow brighter and get warmer again, which can rapidly lead to destructive thermal runaway unless the LED is restrained in some way, by for instance limiting the source voltage so the LED will just never be able to get hot enough. Or, more commonly, by limiting the maximum possible current.

You can see how this can get complicated. (Power-supply design in general is a surprisingly tricky field.) Just running LEDs from a simple DC source via current-limiting resistors can be a bit complex; proper efficient LED drivers that deliver a set current no matter what LED you plug into them are more complicated again. (The drivers in garden lights are elegant, but like the "joule thief", not actually very efficient.)

Don't let all this put you off monkeying with garden lights, though; as Clive says, they're both easy to modify and so cheap that it doesn't matter if you wreck something. Just add some of the incredibly cheap high-brightness LEDs you can get nowadays (which I mentioned the other day), and you can make all sorts of decorative, and even useful, solar LED lights for close to no money at all.