The Biggest
Little Chip
By Charles Platt
Back in 1970, when barely half a dozen corporate seedlings had taken root
in the fertile ground of Silicon Valley, a company named Signetics bought
an idea from an engineer named Hans Camenzind. It wasn’t a breakthrough
concept, just 23 transistors and a bunch of resistors that would function as
a programmable timer. The timer would be versatile, stable, and simple, but
these virtues paled in comparison with its primary selling point. Using the
emerging technology of integrated circuits, Signetics could reproduce the
whole thing on a silicon chip.
This entailed some handiwork. Camenzind
spent weeks using a drafting table and a specially
mounted X-Acto knife to scribe his circuit into a
large plastic sheet. Signetics then reduced this
image photographically, etched it into tiny wafers,
and embedded each wafer in a half-inch rectangle
of black plastic with the product number printed
on top. Thus, the 555 timer was born.
It turned out to be the most successful chip in
history, in both the number of units sold (tens
of billions, and counting) and the longevity of its
design (unchanged in almost 40 years). The 555
has been used everywhere from toys to spacecraft.
It can make lights flash, activate alarm systems,
put spaces between beeps, and create the beeps
themselves. Today, you can buy a single chip online
for about 25 cents.
For the introductory project described below, you
can use the 555CN, Fairchild LM555CN or KA555,
Texas Instruments NE555P, or STMicroelectronics
NE555N. The brand makes no difference. Each
manufacturer offers a Complimentary Metal-Oxide
Semiconductor (CMOS) version, a dual version, and a
surface-mount version in addition to the old-style chip
that stands on eight metal legs spaced 1/10" apart. For
various reasons, you should use the old-style version.
First I’ll show how the 555 can make an LED
flash on and off. Then I’ll adapt it to generate a musical tone, and finally I’ll chain three 555s together
to create a gadget you can use to impose a time
limit in nonvideo games such as checkers or
Scrabble. At the end of a preset interval, the timer
will make a groaning sound to tell a tardy com- petitor that his time’s up and his turn is over. >>
Photography and illustrations by Charles Platt
62 Make: Volume 10
