A chemistry kit from Kosmos (a German company that still makes them) was one of several my parents gave me, and I used it intensively for several years. Here’s a picture of the kit itself:
(both pictures are courtesy of Hugo Rune). Several compounds, notably sulfuric acid, nitric acid and hydrochloric acid, were not sold with the kit – for safety reasons – and my father obtained them at his company. I soon learned that there were a few chemical supply houses in town, where I could buy extra test tubes, glass and rubber tubing, and replacement chemicals.
As far as “safety reasons” go, I believe that almost none of those chemicals would be allowed today. To quote one manufacturer of modern kits (from the New York Times piece):
Basically, you have to be able to eat everything in the science kit.
I suppose that for today’s kids, with their nanosecond attention spans, atrophied self-preservation instincts and parents who sue anybody at the drop of a hat, these precautions are necessary. For myself, I was used to seeing my father handle dangerous tools and substances in his workshop, and although I had a few scares with exploding reagents, nothing serious happened. For a few years – until I discovered that there were actual computers available outside of science-fiction books – I even thought I would pursue chemistry as a career.
Even so, this kit was extremely important and life-changing for me. At the time, my father still smoked occasionally – this was in the early 1960s. My kit included a simple glass aspirator pump (it’s not on the above parts list, for some reason), and I noticed that one of the glass tubes had a flared end that was the exact fit for a cigarette. I hooked the pump up to most of my glass tubes and soon had a primitive cigarette-smoking machine. The pump vacuum was strong enough that a lighted cigarette was smoked down to a nub in less than a minute! But the most impressive result was that the tubes were completely clogged with a black, foul-smelling, viscous substance.
Cleaning the tar out of my precious tubes made me strongly resolve to never start smoking in any form, and I think that my father stopped smoking very soon after seeing the results of that experiment. Maybe some educator should consider selling such smoking machine kits; the episode was certainly decisive for me.
I also fondly recall several other science/engineering kits from my childhood. My chemistry kit, unfortunately, no longer exists, but I still have the Märklin Metallbaukasten I got at the age of 3 (and even use it now and then)! I also had a Lectron Elektronik kit, several other electronic kits from Brazilian companies (Heathkits were, unfortunately, unavailable), and uncountable puzzles and educational games. We also subscribed to several magazines about such subjects.
In retrospect, I’m extremely grateful to my parents in making these and other materials available to me under difficult circumstances.
Update: just found a scholarly paper by Daniel Wolf about science kits (in German); very interesting.
Time flies. Our 4-week trip to the US Southwest’s parks has been over for almost 2 weeks already. The trip itself was marvelous; one of the best in recent years, even though we had to skip a few parks – it was just too tiring. At least we now have a shorter list of places to revisit in the future. We then rested for a week in Denver and nearby Boulder, which are wonderful places, too. All in all we drove about 5000km (3000 miles). Here’s my updated map of visited US states:
Wow, today is the 10th anniversary of this blog; at least that’s the oldest post still preserved in my database. Most of the pieces were already in place in early 2002, but it took me some time to get everything running. At the time, I based the blog on phpbb, but a few years ago I migrated to WordPress; only the support forums, which get very little use these days, still use phpbb. Here’s a screenshot of the early days:
The cringe-inducing title was patterned after several similar ones I saw at the time; later on, no doubt under the influence of Iain M. Banks, I changed to the current “Solipsism Gradient”, which I still think quite descriptive. I’m still working up the nerve to ask him to use the name in an upcoming book, though…
But earlier versions were still more cringe-inducing, look at this one, from mid-2000:
At least I can safely say there’s no <blink> tag, and the animated GIF for the visitor counter was actually well-received; can’t really use it again as there are too few digits to be future-proof, but here’s what it looked like:
This post has been updated several times (last update was on Feb.8, 2013); be sure to scroll to the end.
One central feature of any connector/plug is the pincount. The ubiquitous AC plugs we all know from an early age have 2 (or, more usually, 3) easily visible pins and of course the AC outlet is supposed to have the same number – and, intuitively, we know that the cable itself has the same number of wires. Depending on where you live, you may also be intimately familiar with adapters or conversion cables that have one type of plug on one end and a different type on the other. Here’s one AC adapter we’ve become used to here in Brazil, after the recent (and disastrous) change to the standard:
Even with such a simple adapter – if you open it, there’s just three metal strips connecting one side to the other – mistakes can be made. This specific brand’s design is faulty, assuming that the two AC pins are interchangeable. This is true for 220V, but in an area where 110V is used, neutral and hot pins will be reversed, which can be dangerous if you plug an older 3-pin appliance into such an adapter.
Still, my point here is that everybody is used to cables and adapters that are simple, inexpensive, and consist just of wires leading from one end to the other – after all, this is true for USB, Ethernet, FireWire, and so forth. Even things like DVI-VGA adapters seem to follow this pattern. But things have been getting more complicated lately. Even HDMI cables, which have no active components anywhere, transmit data at such speeds that careful shielding is necessary, and cable prices have stayed relatively high; if you get a cheap cable, you may find out that it doesn’t work well (or at all).
The recent Thunderbolt cables show the new trend. Thunderbolt has two full-duplex 10Gbps data paths and a low-speed control path. This means that you need two high-speed driver chips on each end of the cable (one next to the connector, one in the plug). This means that these cables sell in the $50 price range, and it will take a long time for prices to drop even slightly.
DisplayPort is an interesting case; it has 1-4 data paths that can run at 1.3 to 4.3Gbps, and a control path. The original connector had limited adoption and when Apple came out with their smaller mini version, it was quickly incorporated into the standard, and also reused for Thunderbolt. An even smaller version, called MyDP, is due soon. Analogix recently came out with an implementation of MyDP which they call SlimPort. MyDP is intended for mobile devices and squeezes one of the high-speed paths and the control paths down to 5 pins, allowing it to use a 5-pin micro-USB connector. Here’s a diagram of the architecture on the device side:
If you read the documentation carefully, right inside the micro-USB plug you need a special converter chip which converts those 3 signals to HDMI, and from then on, up to the other end of the cable, you have shielded HDMI wire pairs and a HDMI connector. Of course, this means that you can’t judge that cable by the 5 pins on one end, nor can you say that that specific implementation “transmits audio/video over USB”. It just repurposes the connector. Such a cable would, of course, be significantly more expensive to manufacture than the usual “wires all the way down” cable, and (because of the chip) even more than a standard HDMI cable.
Still referring to the diagram above, if you substitute the blue box (DisplayPort Transmitter) for another labeled “MHL Transmitter”, you have the MHL architecture, although some implementations use an 11-pin connector. Common to both MHL and MyDP is the need for an additional transmitter (driver) chip as well as a switcher chip that goes back and forth between that and the USB transceivers. This, of course, implies additional space on the device board for these chips, traces and passive components, as well as increased power consumption. You can, of course, put in a micro-HDMI connector and drive that directly, that would save neither space nor power.
Is there another way to transmit audio/video over a standard USB implementation? There are device classes for that, but they’re mostly capable of low-bandwidth applications like webcams; at least for USB2. Ah, but what of USB3? That has serious bandwidth (5Gbps) that certainly can accommodate large-screen, quality video, as well as general high-speed data transfer – not up to Thunderbolt speeds, though. You need a USB3 transceiver chip in the blue box above, and no switcher chip; USB3 already has a dedicated pin pair for legacy USB2 compatibility. All that’s needed is the necessary bandwidth on the device itself; and here’s where things start to get complicated again.
You see, there’s serious optimization already going on between the processor and display controller – in fact, all that is on a single chip, the SoC (System-on-a-Chip), labelled A6 in the iFixit teardown. Generating video signals in some standard mode and pulling it out of the SoC needs only a few added pins. If you go the extra trouble to also incorporate a USB3 driver on the SoC and a fast buffer RAM to handle burst transfers of data packets, the SoC can certainly implement the USB3 protocols. But – and that’s the problem – unlike video, that data doesn’t come at predictable times from predictable places. USB requires software to handle the various protocol layers, and between that and the necessity to, at some point, read or write that data to and from Flash memory, you run into speed limits which make it unlikely that full USB3 speeds can be handled by current implementations.
But, even so, let’s assume, for the sake of argument, that the A6 does implement all this and that both it and the Flash memory can manage USB3 speeds. Will, then, a Lightning-to-USB3 cable come out soon? Is that even possible? (You probably were wondering when I would get around to mentioning Lightning…)
Here’s where the old “wires-all-the-way-down” reflexes kick in, at least if you’re not a hardware engineer. To quote from that link:
Although it’s clear at this point that the iPhone 5 only sports USB 2.0 speeds, initial discussions of Lightning’s support of USB 3.0 have focused on its pin count—the USB “Super Speed” 3.0 spec requires nine pins to function, and Lightning connectors only have eight.
…The Lightning connector itself has two divots on either side for retention, but these extra electrical connections in the receptacle could possibly be used as a ground return, which would bring the number of Lightning pins to the same count as that of USB 3.0—nine total.
(…followed, in the comments, by discussions of shields and ground returns and…)
Of course, that contains the following failed assumptions (beyond what I just mentioned):
These assumptions also underlie the oft-cited intention of “waiting for the $1 cables/adapters”. But, recall that Apple specifically said that Lightning is an all-digital, adaptive interface. USB3 is not adaptive, although it can be called digital in that it has two digital signal paths implemented as differential pairs. If you abandon assumptions 1 and 2, assumption 3 becomes just silly. Remember, the SlimPort designers put a few simple digital signals on the connector and converted them – just a cm or so away – into another standards’ differential wire pairs by putting a chip inside the plug.
I’ll be seriously surprised if even one of those points is not verified when the specs come out. And this is what is meant by “future-proof”. Re-using USB and micro-USB (or any existing standard) could never do any of that.
Update: just saw this article which purports to show the pinouts of the current Lightning-to-USB2 cable. “…dynamically assigns pins to allow for reversible use” is of course obvious, if you put together the “adaptive” and “reversible” points from this picture of the iPhone 5 event. Regarding the pinout they published, it’s not radially symmetrical as I thought it would be (except for
one two pins), so I really would like a confirmation from some site like iFixit (I hear they’ll do a teardown soon). They also say:
Dynamic pin assignment performed by the iPhone 5 could also help explain the inclusion of authentication chips within Lighting cables. The chip is located between the V+ contact of the USB and the power pin of the Lightning plug.
I really see no justification for the “authentication chip” hypothesis, and even their diagram doesn’t show any single “power pin of the Lightning plug”. It’s clear that, once the cable’s type has been negotiated with the device, and the device has checked if there’s a charger, a peripheral or a computer on the other end, the power input from the USB side is switched to however many pins are required to carry the available current.
Update#2: I was alerted to this post, which states:
The iPhone 5 switches on by itself, even when the USB end [of the Lightning-to-USB cable] is not plugged in.
Hm. This would lend weight to my statement that a configuration protocol between device and Lightning plug runs just after plug-in – after all, such a protocol wouldn’t work with the device powered off. It also means that the protocol is implemented in software on the device side; otherwise they could just run it silently, until it really appears that the entire device needs to power up.
Still, there’s the question of what happens when the device battery is entirely discharged. I suppose there’s some sort of fallback circuit that allows the device to be powered up from the charger in that case.
Finally, I’ve just visited an Apple Store where I could get my first look at an iPhone 5. The plug is really very tiny but looks solid.
Update#3: yet another article reviving the authentication chip rumor. Recall how a similar flap about authentication chips in Apple’s headphone cables was finally put to rest? It’s the same thing; the chip in headphones simply implemented Apple’s signalling protocol to control iPods from the headphone cable controls. The chip in the Lightning connector simply implements Apple’s connector recognition protocol and switches charging/supply current.
Apple is building these chips in quantity for their own use and will probably make them available to qualified MFi program participants at cost – after all, it’s in their interest to make accessories widely available, not “restrain availability”.
Now, we hear that “only Apple-approved manufacturing facilities will be allowed to produce Lightning connector accessories”. That makes sense in that manufacturing tolerances on the new connector seem to be very tight and critical. Apple certainly wouldn’t want cheap knock-offs of the connector causing shorts, seating loosely or implementing the recognition protocol in a wrong way; this would reflect badly on the devices themselves, just as with apps. Think of this as the App Store for accessory manufacturers.
Update#4: new articles have come out with more information, confirming my reasoning.
The folks at Chipworks has done a more professional teardown, revealing that the connector contains, as expected, a couple of power-switching/regulating chips, as well as a previously unknown TI BQ2025 chip, which appears to contain a small amount of EPROM and implements some additional logic, power-switching, and TI’s SDQ serial signalling interface. SDQ also uses CRC checking on the message packets, so a CRC generator would be on the chip. Somewhat confusingly, Chipworks refer to CRC as a “security feature”, perhaps trying to tie into the authentication angle, but of course any serial protocol has some sort of CRC checking just to discard packets corrupted by noise.
Anandtech has additional information:
Apple calls Lightning an “adaptive” interface, and what this really means are different connectors with different chips inside for negotiating appropriate I/O from the host device. The way this works is that Apple sells MFi members Lightning connectors which they build into their device, and at present those come in 4 different signaling configurations with 2 physical models. There’s USB Host, USB Device, Serial, and charging only modes, and both a cable and dock variant with a metal support bracket, for a grand total of 8 different Lightning connector SKUs to choose from.
…Thus, the connector chip inside isn’t so much an “authenticator” but rather a negotiation aide to signal what is required from the host device.
Finally, there’s the iFixit iPod Nano 7th-gen teardown. What’s important here is that this is the thinnest device so far that uses Lightning, and it’s just 5.4mm (0.21″) thick. From the pictures you can see that devices can’t get much thinner without the connector thickness becoming the limiting factor.
Update#5: the Wikipedia article now shows a supposedly definite pin-out (and the iFixit iPhone 5 teardown links to that). Although I can’t find an independent source for the pin-out, it shows two identification pins, two differential data lanes, and a fixed power pin. Should this be confirmed it would mean that the connector is less adaptive in regarding to switching data and power pins; on the other hand, that pinout may well be just an indication of the default configuration for USB-type cables (that is, after the chips have negotiated the connection).
The cool folks at iFixit have now published their comprehensive teardown of the iPhone 5. (Hopefully the other 2 new devices will also be done soon.)
Here’s a detail view of the Lightning connector inside the case: (click on all images to see the hires version from their site)
Notice two screws securing the connector body to the device case, and the metal bracket that keeps the other end from flexing. Here’s a closeup of the disassembled connector and of the plug:
Remember that the inside of the case is milled out of a solid block of metal, so this design looks to be much less breakable than the old 30pin version – I’ve been told that the tab end of the plug also feels very sturdy. Here’s a close-up of both connectors:
The space savings are considerable. I read that Apple has no plans to do a dock, so this looks to be a third-party opportunity. The previous connector had no serious protection against flexing, so previous docks had to grip the back and bottom of the device, which also led to a profusion of plastic dock adapters; Lightning docks should be able to get away with just a simple generic back support.
Confirming the rest of my speculations regarding the “adaptive” part of the Lightning interface will have to wait until the specifications leak… stay tuned.
Update: just saw a report about a teardown of the Lightning plug: “Peter from Double Helix Cables took apart the Lightning connector and found inside what appear to be authentication chips. He found a chip located between the V+ contact of the USB and the power pin on the new Lightning plug.”
It’s interesting how people assume that Lightning is just a pin-compatible extension of USB (which also explains why they feel that a cable should cost only a dollar or two). Note also that nobody knows for sure yet which pin is “the power pin”. Unfortunately the picture is very unclear ; it seems that there are three chips and a few passive components, at least on that side. Which, of course, goes far to confirm my hypothesis that the cable contains circuitry to tell the device which sort of adapter/cable is connected, as well as signal drivers/conditioners for USB2 (for this specific cable). The large chip, if it is really “directly in the signal path of the V+ wire”, probably switches the charging current to the appropriate pins on the device, once the interface has adapted to the cable – all this “authentication chip” paranoia is just – paranoia.
Update#2: it says here: “Included in the new high-tech part is a unique design which the analyst says is likely to feature a pin-out with four contacts dedicated to data, two for accessories, one for power and a ground. Two of the data transmission pins may be reserved for future input/output technology like USB 3.0 or perhaps even Thunderbolt, though this is merely speculation.”
See what I mean about people thinking that all pins are equal? What do they think that “adaptive” means, anyway?
Update#3: John Siracusa and Dan Benjamin agreed with my points in their latest talk show (references start just after the 49:00 mark) and they even sorta pronounced my name right. Thanks guys!
Update#4: found a good discussion of the Lightning (published over a month ago!), with somewhat blurry pictures of a disassembled Lightning plug. They seem to match well with the linked pictures in the first update, above.
Update#5: my final summary. Please comment there, comments here are now closed.