The 555 Man
By Charles Platt
While fact-checking Make: Electronics, I realized I didn’t have permission to publish a photograph that I’d found of Hans Camenzind, designer of the 555 chip. This led me to a telephone conversation that was a true delight, leaving me smiling foolishly for hours afterward.
I included a brief history of the 555 in my book, and wanted to illustrate it with a photograph of its creator, Hans Camenzind. I Googled him and found that he has his own plain-and-simple webpage. And because the page not only included his email address but also his personal phone number, I impulsively dialed it. (I should add: Please don’t do this yourself, unless you have a specific, useful purpose. It would not be polite to take up someone’s time just because he’s generous enough to publish his number.)
A couple of seconds later, I was amazed when a gentleman with a Swiss accent answered the phone. It was a truly strange moment. For literally decades, I’ve known about the 555 timer and used it in projects. I understand more about the behavior of this chip than any other. And suddenly, without warning, here I was speaking to the man who had single-handedly created it.
I got the impression of a very alert intelligence at the other end of the line, which shouldn’t have been surprising. He was friendly, modest, and more than willing to help me by signing a release entitling us to use his photograph. However, I got the impression that he had little interest in chit-chat, and really, I didn’t have much more to say, other than to thank him for his role in that amazing and wonderful community of engineers of the 60s and 70s who had the vision and the audacity to develop the smart little circuits that took astronauts to the moon, ushered in the era of desktop computers, and facilitated the internet.
Hans Camenzind’s name may not be familiar to most people — certainly not as familiar as that of William Shockley, who co-invented the transistor, or Andy Grove, who played such a key role in the development of Intel. Yet Camenzind’s work in the early days of Silicon Valley turned out to be unexpectedly significant.
In 1970, he sold an idea to a company called Signetics for a new kind of timer. A timer may seem a lowly thing, merely measuring milliseconds and emitting pulses at regular intervals. What made Camenzind’s concept so significant was that his circuit, containing 23 transistors and assorted resistors, could be scaled down and etched onto a wafer of silicon. In fact, it pushed the state of the art at the time. It was the first chip of its kind.
Camenzind developed it single-handedly, and he did it the hard way. First, he designed the circuit using full-scale components. When he verified that it worked, he started substituting components of slightly different values, to make sure that it would still work if the chip-manufacturing process introduced inaccuracies. He made at least ten versions of the circuit. Testing took months.
Having finalized the circuit, his next step was to cut it into plastic film using an X-Acto knife. This was long before the days of computer drawing software. Everything had to be done painstakingly by hand. From start to finish, the whole development process took about a year.
When that phase was complete, the circuits were reduced in size photographically, by a factor of about 300:1, and used as masks for etching the silicon. Each silicon wafer was sealed into a half-inch rectangle of black plastic, and the sales manager at Signetics assigned a product identification code of 555. The 555 timer was born.
It has turned out to be the most successful chips in history, both in the number of units sold (tens of billions, and still counting) and the longevity of its design (fundamentally unchanged for almost forty years). Even now, about a billion 555s are manufactured each year.
In Make: Electronics, I decided to include the 555, because it remains so fundamental. It’s also a wonderful teaching tool, since it can be used in so many ways. If you want to build, say, a reaction timer, using a counter and a couple of logic chips, you’re going to run it with a 555 timer, and you may end up adding a couple more 555s to take care of functions such as delaying the start of the count and locking the display until a reset button is pressed. You can also run a 555 fast enough to generate audible tones, which can be incorporated into a burglar alarm, or you can use it in a combination lock. All three of these projects are included in the book.
It’s true that programmable microcontroller units (MCUs) can do the same thing as a 555, with fewer components. You simply write a little program and download it into the MCU’s flash memory, and if you want to make future modifications, you edit the program and download it again. On the other hand, as soon as you get involved with software, you have a whole set of new potential problems–such as syntax errors, logical errors, or runtime overflow when your program adds two numbers and the result turns out to be too big for the variable that you allocated. There’s really nothing as elegantly simple as a circuit built entirely in hardware. And I think this is still the best way to learn the fundamentals.
I have so much respect for the pioneers in what later came to be known as Silicon Valley, and I’m thrilled that for a few moments, I spoke to someone whose design has been incorporated into devices ranging from space vehicles to toaster ovens. Thank you, Hans Camenzind, for the part you played in changing all of our lives!
If you want to know more, there’s a great interview transcript with Hans at the Semiconductor Museum.
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