Computer handwriting recognition is very cool by itself, and it’s something that we’d like to incorporate into a project. So we went digging for hacker solutions, and along the way came up with an interesting bit of history and some great algorithms. We feel like we’ve got a good start on that front, but we’re stuck on the hardware tablet sensor itself. So in this Ask Hackaday, we’re going to make the case for why you could be using a tablet-like device for capturing user input or doing handwriting recognition, and then we’re going to ask if you know of any good DIY tablet designs to make it work.
In the early 1930s, Reginald Denny, an English actor living in Los Angeles, stumbled upon a young boy flying a rubber band-powered airplane. After attempting to help the boy by adjusting the rubber and control surfaces, the plane spun into the ground. Denny promised he would build another plane for the boy, and wrote to a New York model manufacturer for a kit. This first model airplane kit grew into his own hobby shop on Hollywood Boulevard, frequented by Jimmy Stewart and Henry Fonda.
The business blossomed into Radioplane Co. Inc., where Denny designed and built the first remote controlled military aircraft used by the United States. In 1944, Captain Ronald Reagan of the Army Air Forces’ Motion Picture unit wanted some film of these new flying targets and sent photographer David Conover to the Radioplane factory at the Van Nuys airport. There, Conover met Norma Jeane Dougherty and convinced her to go into modeling. She would later be known as Marilyn Monroe. The nexus of all American culture from 1930 to 1960 was a hobby shop that smelled of balsa sawdust and airplane glue. That hobby shop is now a 7-Eleven just off the 101 freeway.
Science historian James Burke had a TV wonderful show in the early 90s – Connections – where the previous paragraphs would be par for the course. Unfortunately, the timbre of public discourse has changed in the last twenty years and the worldwide revolution in communications allowing people to instantaneously exchange ideas has only led to people instantaneously exchanging opinions. The story of how the Dutch East India Company led to the rubber band led to Jimmy Stewart led to remote control led to Ronald Reagan led to Death of a Salesman has a modern fault: I’d have to use the word ‘drone’.
The word ‘propaganda’ only gained its negative connotation the late 1930s – it’s now ‘public relations’. The phrase ‘global warming’ doesn’t work with idiots in winter, so now it’s called ‘climate change’. Likewise, quadcopter pilots don’t want anyone to think their flying machine can rain hellfire missiles down on a neighborhood, so ‘drone’ is verboten. The preferred term is quadcopters, tricopters, multicopters, flying wings, fixed-wing remote-controlled vehicles, unmanned aerial systems, or toys.
I’m slightly annoyed by this and by the reminder I kindly get in my inbox every time I use the dreaded d-word. The etymology of the word ‘drone’ has nothing to do with spying, firing missiles into hospitals, or illegally killing American civilians. People like to argue, though, and I need something to point to when someone complains about my misuse of the word ‘drone’. Instead of an article on Hollywood starlets, the first remote control systems, and model aviation, you get an article on the etymology of a word. You have no one else to blame but yourself, Internet.
The news has been full of reports that the last company manufacturing consumer VCRs will cease making them this year. I think most of us are surprised that the event is only happening now. After all, these days, video recording is likely to be on a hard drive, a USB stick, or on a server somewhere. Even recording to DVDs seems a bit quaint these days.
Back before there were web sites, people had to get information from magazines like Popular Electronics, Radio Electronics, and a few others. In the late 1960s and early 1970s, it was common to see these magazines predict that this would be the year of the home video recording system. For example, in 1971, [Lou Garner] wrote: “…they [Sony] hope will put home videotape playing in the same living room as conventional high-fidelity sound systems.” You should know that the video cassette he was talking about was 8 inches wide by 5 inches deep (a big larger than a VHS tape) and contained 3/4 inch magnetic tape (VHS used 1/2 inch tape). The 32-pound player had a retail price of about $350 (about $2,000 in today’s dollars; remember gas was $0.36 a gallon and eggs were $0.53 a dozen). It would be several years before VHS and Betamax would duke it out for home supremacy.
When the story of an invention is repeated as Received Opinion for the younger generation it is so often presented as a single one-off event, with a named inventor. Before the event there was no invention, then as if by magic it was there. That apple falling on Isaac Newton’s head, or Archimedes overflowing his bath, you’ve heard the stories. The inventor’s name will sometimes differ depending on which country you are in when you hear the story, which provides an insight into the flaws in the simple invention tales. The truth is in so many cases an invention does not have a single Eureka moment, instead the named inventor builds on the work of so many others who have gone before and is the lucky engineer or scientist whose ideas result in the magic breakthrough before anyone else’s.
The history of computing is no exception, with many steps along the path that has given us the devices we rely on for so much today. Blaise Pascal’s 17th century French mechanical calculator, Charles Babbage and Ada, Countess Lovelace’s work in 19th century Britain, Herman Hollerith’s American tabulators at the end of that century, or Konrad Zuse’s work in prewar Germany represent just a few of them.
So if we are to search for an inventor in this field we have to be a little more specific than “Who invented the first computer?”, because there are so many candidates. If we restrict the question to “Who invented the first programmable electronic digital computer?” we have a much simpler answer, because we have ample evidence of the machine in question. The Received Opinion answer is therefore “The first programmable electronic digital computer was Colossus, invented at Bletchley Park in World War Two by Alan Turing to break the Nazi Enigma codes, and it was kept secret until the 1970s”.
It’s such a temptingly perfect soundbite laden with pluck and derring-do that could so easily be taken from a 1950s Eagle comic, isn’t it. Unfortunately it contains such significant untruths as to be rendered useless. Colossus is the computer you are looking for, it was developed in World War Two and kept secret for many years afterwards, but the rest of the Received Opinion answer is false. It wasn’t invented at Bletchley, its job was not the Enigma work, and most surprisingly Alan Turing’s direct involvement was only peripheral. The real story is much more interesting.
The recent movie “The Imitation Game” gave [Alan Turing] some well-deserved fame among non-computer types (although the historical accuracy of that movie is poor, at best; there have been several comparisons between the movie and reality). However, for people in the computer industry, Turing was famous for more than just helping to crack Enigma. His theoretical work on computing led to the Turing machine, which is still an important concept for reasoning about computers in a mathematical way. He also laid the foundation for the stored program computer that we take for granted today.
What’s a Turing Machine?
A Turing machine is deceptively simple and, like many mathematical models, highly impractical. Leading off the inpracticalities, the machine includes an infinite paper tape. There is a head that can read and write any symbol to the tape at some position, and the tape can move to the left or the right. Keep in mind that the head can write a symbol over another symbol, so that’s another practical difficulty, although not an insurmountable one. The other issue is that the symbol can be anything: a letter, a number, a jolly wrencher, or a bunch of dots. Again, not impossible, but difficult to do with practical hardware implementations.
The history of the diode is a fun one as it’s rife with accidental discoveries, sometimes having to wait decades for a use for what was found. Two examples of that are our first two topics: thermionic emission and semiconductor diodes. So let’s dive in.
Vacuum Tubes/Thermionic Diodes
Our first accidental discovery was of thermionic emission, which many years later lead to the vacuum tube. Thermionic emission is basically heating a metal, or a coated metal, causing the emission of electrons from its surface.
Electroscope
In 1873 Frederick Guthrie had charged his electroscope positively and then brought a piece of white-hot metal near the electroscope’s terminal. The white-hot metal emitted electrons to the terminal, which of course neutralized the electroscope’s positive charge, causing the leafs to come together. A negatively charged electroscope can’t be discharged this way though, since the hot metal emits electrons only, i.e. negative charge. Thus the direction of electron flow was one-way and the earliest diode was born.
Thomas Edison independently discovered this effect in 1880 when trying to work out why the carbon-filaments in his light bulbs were often burning out at their positive-connected ends. In exploring the problem, he created a special evacuated bulb wherein he had a piece of metal connected to the positive end of the circuit and held near the filament. He found that an invisible current flowed from the filament to the metal. For this reason, thermionic emission is sometimes referred to as the Edison effect.
Thermionic diode. By Svjo [CC BY-SA 3.0], via Wikimedia CommonsBut it took until 1904 for the first practical use of the effect to appear. John Ambrose Fleming had actually consulted for the Edison Electric Light Company from 1881-1891 but was now working for the Marconi Wireless Telegraph Company. In 1901 the company demonstrated the first radio transmission across the Atlantic, the letter “S” in the form or three dots in Morse code. But there was so much difficulty in telling the received signal apart from the background noise, that the result was disputed (and still is). This made Fleming realize that a more sensitive detector than the coherer they’d been using was needed. And so in 1904 he tried an Edison effect bulb. It worked well, rectifying the high frequency oscillations and passing the signals on to a galvanometer. He filed for a patent and the Fleming valve, the two element vacuum tube or thermionic diode, came into being, heralding decades of technological developments in many subsequent types of vacuum tubes.
Vacuum tubes began to be replaced in power supplies in the 1940s by selenium diodes and in the 1960s by semiconductor diodes but are still used today in high power applications. There’s also been a resurgence in their use by audiophiles and recording studios. But that’s only the start of our history.
Transistors have come a long way. Like everything else electronic, they’ve become both better and cheaper. According to a recent IEEE article, a transistor cost about $8 in today’s money back in the 1960’s. Consider the Regency TR-1, the first transistor radio from TI and IDEA. In late 1954, the four-transistor device went on sale for $49.95. That doesn’t sound like much until you realize that in 1954, this was equivalent to about $441 (a new car cost about $1,700 and a copy of life magazine cost 20 cents). Even at that price, they sold about 150,000 radios.
Part of the reason the transistors cost so much was that production costs were high. But another reason is that yields were poor. In some cases, 4 out of 5 of the devices were not usable. The transistors were not that good even when they did work. The first transistors were germanium which has high leakage and worse thermal properties than silicon.
Early transistors were subject to damage from soldering, so it was common to use an alligator clip or a specific heat sink clip to prevent heat from reaching the transistor during construction. Some gear even used sockets which also allowed the quick substitution of devices, just like the tubes they replaced.
When the economics of transistors changed, it made a lot of things practical. For example, a common piece of gear used to be a transistor tester, like the Heathkit IT-121 in the video below. If you pulled an $8 part out of a socket, you’d want to test it before you spent more money on a replacement. Of course, if you had a curve tracer, that was even better because you could measure the device parameters which were probably more subject to change than a modern device.
Of course, germanium to silicon is only one improvement made over the years. The FET is a fundamentally different kind of transistor that has many desirable properties and, of course, integrating hundreds or even thousands of transistors on one integrated circuit revolutionized electronics of all types. Transistors got better. Parameters become less variable and yields increased. Maximum frequency rises and power handling capacity increases. Devices just keep getting better. And cheaper.
A Brief History of Transistors
The path from vacuum tube to the Regency TR-1 was a twisted one. Everyone knew the disadvantages of tubes: fragile, power hungry, and physically large, although smaller and lower-power tubes would start to appear towards the end of their reign. In 1925 a Canadian physicist patented a FET but failed to publicize it. Beyond that, mass production of semiconductor material was unknown at the time. A German inventor patented a similar device in 1934 that didn’t take off, either.
Replica of the First Transistor
Bell labs researchers worked with germanium and actually understood how to make “point contact” transistors and FETs in 1947. However, Bell’s lawyers found the earlier patents and elected to pursue the conventional transistor patent that would lead to the inventors (John Bardeen, Walter Brattain, and William Shockley) winning the Nobel prize in 1956.
Two Germans working for a Westinghouse subsidiary in Paris independently developed a point contact transistor in 1948. It would be 1954 before silicon transistors became practical. The MOSFET didn’t appear until 1959.
Of course, even these major milestones are subject to incremental improvements. The V channel for MOSFETs, for example, opened the door for FETs to be true power devices, able to switch currents required for motors and other high current devices.
