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Probably the most enduringly profitable chip in electronics historical past was created by one man working in a back-alley storefront. His title was Hans Camenzind, the chip was the 555 timer, and this 12 months marks its fiftieth anniversary. It has outlasted all rivals, continues to be being manufactured in mainly the identical design, and has offered billions worldwide.
The 555 has endured as a result of it’s amazingly versatile and dependable. It might probably time an interval starting from a millisecond to an hour — or can generate a pulse stream at a frequency exceeding 1MHz. It might probably create audio tones, and might even operate as a logic gate. I take into account it so essential, regardless of its age, I devoted two chapters to it and a number of other experiments in my e-book Make: Electronics.
A through-hole 555 chip measures about 0.4″×0.3″. Floor-mount variations have similar pin features. [Figure A]
Contained in the Apple II, the blink charge of the cursor was managed by a 555. It has set the delay of intermittent automotive windshield wipers, and has been utilized in spacecraft. Actually the SE555-SP variant, nonetheless accessible from Texas Devices, is space-rated. The on a regular basis model in Determine A at the moment retails for 50 cents apiece, whereas on AliExpress, generic 555s are 10 for $1.
Hans Camenzind, in 1971 when he was creating the 555, and in 2002.
Origins
Within the late Sixties, Camenzind was questioning methods to put an AM radio receiver on a chip. Usually a receiver makes use of inductors to discriminate between broadcast frequencies, however inductance is troublesome to construct into an built-in circuit.
He thought that somebody, someplace will need to have made a tuned circuit that didn’t require an inductor, so he spent a number of days looking out the MIT library in Boston, the place he lastly discovered the reply: A 1935 article describing an almost-forgotten idea known as a phase-locked loop. This might generate such a exact frequency, he realized it could possibly be used for one thing extra fascinating than a radio. It might be superb for an oscillator, or a timer.
He took his concept with him when he relocated along with his spouse and youngsters to the Bay Space to affix Signetics, an upstart firm that was attempting to compete with Fairchild Semiconductor, the business chief. However after two years, Hans turned impatient with their “stodgy” angle. He accepted a wage minimize, turned an impartial marketing consultant, rented his storefront, and got down to pursue his dream.
He constructed benches and cabinets with boards from a lumber retailer, and since his spouse, Pia, was an accountant, she did the bookkeeping. “He had a stipend of $1,200 monthly from Signetics,” Pia recollects. “We minimize our bills to the minimal. We by no means went out to dinner. However I assumed — he wants to do that.”
Hans was 36, had 4 youngsters, and $400 within the financial institution. Later, he described his resolution as “reckless.” Nonetheless, he got here up with a circuit, and breadboarded it utilizing on a regular basis transistors and resistors. He then examined it utilizing tools loaned by Signetics, and tried limitless iterations, various the element values as a result of he needed it to work even when the manufacturing course of launched errors.
Having perfected the circuit, he began on essentially the most arduous half. Chip manufacturing requires a number of photographic masks when layers of silicon are partially etched away. In 1971, the one strategy to make the masks was by reducing them into plastic movie often known as rubylith, utilizing an X-Acto knife at a scale of perhaps 400:1.
Even at Intel, the vastly extra advanced 4004 (the primary true microprocessor) was fabricated from hand-cut masks, as a result of computer-aided design didn’t but exist. Hans spent many days hunched over a light-weight desk, reducing plastic and eradicating areas with tweezers.
The Launch
The very first 555. (From the Camenzind photograph assortment.) [Figure B]
When Hans delivered his masks to Signetics, he confronted a brand new downside: Engineers on the firm had been skeptical that anybody wanted a timer chip. Fortuitously, the advertising and marketing supervisor, Artwork Fury, overruled the engineers. It was Fury who assigned the easily-memorized 555 half quantity.
A micrograph of the very first Signetics 555 wafer is proven in Determine B on the next web page. The chip was a direct success, as a result of it labored so effectively. You bought constant outcomes for those who ran it from a 5V provide or 18V. It labored the identical manner when driving a 20mA LED or sourcing 200mA for a small motor.
“Built-in elements have the drawback of being inaccurate,” Hans wrote later. However, “No matter their variation could also be, all of them differ collectively, since they’re made on the identical time and underneath the identical circumstances. In different phrases, they match very effectively. I used that characteristic to construct a novel oscillator, which turned out to be extraordinarily secure.”
Inside a 12 months, different producers had been copying the design. “All people was stealing from everyone else,” Hans recalled, “and in these days, no one paid any consideration to patents.” Actually Signetics didn’t even apply for a patent, fearing that in the event that they tried to implement it, they’d begin a battle with different, bigger firms. As we speak, anybody can construct a duplicate of a 555 timer.
The Legacy
The 555 established Hans Camenzind as an authority on analog built-in circuits. By 2006, he had designed 140 customary and customized chips. He additionally wrote two superb books: The definitive Designing Analog Chips, and a superb normal introduction to electrical energy titled A lot Ado About Nearly Nothing, which included thumbnail biographies of all of the pioneers. Each books are nonetheless accessible on-line by way of print-on-demand.
The 555, in fact, has acquired legendary standing. You may even purchase a equipment to construct your personal macro-scale reproduction from discrete elements.
A voltage spike that happens when bipolar 555 output goes excessive can disturb different elements. (Reproduced from the e-book Make: Electronics by Charles Platt.) [Figure C]
The chip has some well-documented defects. Its use of bipolar transistors leads to a nasty voltage spike when its output transitions (see Determine C), and it’s power-hungry. However a CMOS model has mounted these points.
The storefront the place Hans Camenzind developed the 555, photographed in 2022. (Courtesy of Pia Camenzind.) [Figure D]
Hans Camenzind died in 2012 on the age of 78. As we speak, the storefront the place he designed the timer is occupied by a real-estate dealer (see Determine D). The alley is arrowed within the image of Murphy Avenue in Determine E. Possibly at some point Sunnyvale will honor Hans with a plaque beside his previous office, however within the meantime his genius lives on in tens of billions of chips containing copies of his hand-made circuit.
Location of the alley resulting in the storefront. (Tailored from Google Road View.) [Figure D]
The author thanks the Camenzind household for his or her beneficiant assist, and Jack Ward of the Transistor Museum, the place audio recordsdata of Hans Camenzind are archived right here
Chip Worship
Eric Schlaepfer has a lifelong ardour for classic electronics — particularly cathode-ray tubes, which he has repurposed as useful artwork objects resembling clocks. He speaks lyrically about “the enjoyment of a vectored show, with glowing phosphors.”
However his most generally recognized venture is a macro-scale 555 chip. “I discovered an previous datasheet which confirmed the elements, even together with the resistor values,” he says. “I constructed a duplicate from transistors and resistors, and it labored.” (The circuit is proven in Determine F.)
Schematic of the circuit inside a 555 timer chip, revealed within the authentic Signetics datasheet. [Figure F]
Eric’s massive 555 is a good-looking piece, proven in Determine G. Naturally, he confirmed it to individuals — together with Lenore Edman and Windell Oskay, cofounders of Evil Mad Scientist Laboratories, which sells maker merchandise. Windell has his personal fetish for previous electronics, resembling Nixie tubes, so he and Lenore got here to the apparent conclusion: They may promote Eric’s massive 555 as a equipment.
The unique model of the massive 555 timer, constructed by Eric Schlaepfer. [Figure G]
The assembled model is proven in Determine H, and it’s on the market right here. In case you have regular fingers and good eyesight, there’s additionally a surface-mount model.
The Three Fives equipment compiled by Evil Mad Scientist Laboratories. [Figure H]
Finally, Windell hopes to market a macro-scale 6502 microprocessor containing 3,510 transistors, if he can resolve some irritating element provide points. Within the meantime, he has constructed a CNC-cut, laser-engraved, picket (nonelectronic) 555 footstool, proven in Determine I with non-obligatory cat.
CNC’ed picket 555 footstool (no digital operate). [Figure I]
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