September 1973 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Electronic ignition, computer-controlled
fuel injection and air intake, alarm systems, radar, rear back-up cameras, GPS,
stereo sound systems, Bluetooth tire pressure monitors, hands-free telephones, automatic
headlight directors, drowsy driver detectors, collision avoidance, anti-lock brakes,
fuel efficiency management, air bag deployment, self-parking and even self-driving
features are now or soon will be standard features in automobiles. Mac McGregor
and Barney hit upon a lot of these items - some explicitly, some implicitly - in
this 1973 installment of "Mac's Service Shop" found in Popular Electronics
magazine. Amazingly impressive devices and systems are fermenting in the minds of
engineers and scientists today that will begin appearing in new car models a decade
or decades from now. While I am duly impressed, I would gladly trade my 2011 Jeep
Patriot for a nicely restored 1960s or 1970s pick'em-up truck*. I'll add the desired
newfangled gizmos myself.
* Have you seen the cost of vintage pickup trucks these days - restored or not?
I'm accepting donations ;-)
Unprecedented Opportunities in Automotive Electronics
Mac's Service Shop: Electronics in Automobiles
By John T. Frye, W9EGV, KHD4167
"Mac," Barney said to his boss working at the bench beside him, "what will cars
be like twenty years from now?"
Mac finished a delicate job of desoldering an i-f can from a printed circuit
board before he answered, "No one knows for sure what those cars will look like
or how they will be powered, but this much is certain: they will involve a lot more
electronics than cars do today. Several months ago the American big three automobile
manufacturers forecast that $5 billion annually might be spent on automotive electronics
by 1980, and European manufacturers are talking about 12 percent of car costs going
for electronics by 1982."
"That's not hay you're talking about," Barney reminded him. "I was just reading
that last year we spent $49 billion on autos and parts. Then we spent another $41
billion on gas and oil, repairs, insurance, and other charges. That made a neat
total of $90 billion, or about 11% of our after-tax income. Only food, about 17%,
and housing, about 13%, get a larger share of the American's after-tax dollar. To
ice the cake, consumer sales of autos and parts in the first three months of this
year were up 20% over the same three months of 1972. Some think an unprecedented
fifteen million cars and trucks may be sold this year."
RCA's version of car of the future, showing where solid-state
electronics will be used.
"That's all the more reason why a young fellow like you, who expects to make
his living from electronics, would do well to take a keen interest in this automotive-electronic
field that is just starting to boom. You may be able to get yourself a piece of
"Why are car people discovering electronics now?" Barney asked. "In the past
we've only received
money from the auto people. Radio, headlamp dimmer, voltage regulator, sequential
turn signals, alternator diodes - that was about it."
"There are several hard-headed reasons. In the past, auto design was dominated
by mechanical engineers who were very reluctant to allow outsiders to play a part
in designing the car. But now they need electronic help to meet government-dictated
deadlines for reducing pollution. Only solid-state compactness can provide room
in the already crowded car for new safety and comfort equipment. Modem high-speed,
heavy-traffic driving imposes demands on the average driver that exceed the limitations
of his unaided senses and reaction time; only lightning-fast electronics can amplify
those senses and stretch time for him. Space exploration, by fully demonstrating
the reliability, precision, and space-saving of electronics under extreme conditions
has destroyed many arguments against such use in the car, and plummeting solid-state
costs have undercut others. Finally, the ranks of automotive engineers, historically
trained to think in terms of mechanics. are being infiltrated by space age electronics
engineers. Their influence promises to snowball."
"How about getting out your crystal ball and showing me some of the coming electronic
applications to cars?"
Numbered callouts show locations of components in Chrysler's
electronic security system.
New and Future Applications. "Okay. First I'll switch the crystal
ball to 'local' and talk about applications right at hand. Electronic ignition is
one. Chrysler engineers estimate 15% of the cars on the road have one or more plugs
misfiring, increasing hydrocarbon emission 300 to 1000 per cent. Their electronic
ignition system, now standard on all their cars, is designed to prevent such misfiring.
reluctor and a magnetic pickup coil replace conventional breaker points, cam,
and 'condenser' inside the distributor. Each time a reluctor tooth passes the pole
piece of the pickup coil, this induces a pulse in the coil that causes a switching
transistor to interrupt the primary current of the induction coil, just as happened
when the old breaker points were nudged open by the cam. The rest of the ignition
operation is normal, but notice there are no points and no earn to wear and pit
and corrode so as to degrade the spark and change the timing. Ignition time set
at the factory remains adjusted as long as the distributor is left alone.
"Car theft is another challenge electronics is meeting. Almost a million cars
were stolen in 1971, twice as many as were stolen six years previously. Starting
this year Chrysler offers a new security system built right into the car's basic
electrical system. An attempt to force open the passenger, trunk, or engine compartment
or an unauthorized attempt to start the car causes the horn to start beeping and
the headlights, tail lights, and parking lights to flash on and off.
The same system serves as an occupant distress alarm and provides instant protective
locking. When an emergency button on the instrument panel is pushed, all doors are
instantly locked, the hood latch is blocked, and the visual and audible alarm signals
start and run for three minutes and then stop, but the doors remain locked. This
feature is considered essential because as unoccupied-car protection becomes better,
the frustrated thief may feel the best way to steal a car is to take the key away
from the driver; so chance of assault is mounting. Naturally, details of the system
are not broadcast, but the heart is a well-concealed control box equipped with IC's,
transistors, resistors, power relay, and a capacitor. This box receives a message
from any sensor, interprets the message, decides which of several courses of action
is most appropriate, and initiates the proper action.
"But with more than 55,000 killed and five million injured on the highways annually
automobile safety commands a high priority on the services of electrons, and they
promise to meet the challenge. To help avoid collisions we already have in production
electronic anti-skid brakes, sequential turn signals, engine speed limiters, intermittent
windshield wipers, and headlamp dimmers. If radars can be built cheaply enough,
there are innumerable anti-collision uses for them on cars. Bendix has developed
and Ford is testing an adaptive speed-control system that uses a CW Doppler radar
and a computer that computes range and range-change-rate between one car and another
in front. Connected to the accelerator and brakes, it automatically slows a car
when it is getting too close to the car in front; and if a marked deceleration is
noted in the car ahead, the brakes of the trailing car are applied. To prevent false
readings from cars in adjacent lanes, the Doppler beam is restricted to about 4
degrees, which is lane width at 200 to 250 feet. Responders on the rears of cars
return the sensing signals in some systems.
"Cheap radars will be used in the rear and sides of the car to warn the driver
of other cars approaching from behind in adjacent lane blind spots or of objects
behind him when he is backing. Here a wide beam, up to 180 degrees, will be used.
In tests Bendix has detected a one-pound coffee can at 15 feet. Other collision-avoiding
electronic devices of the future include a light-amplifying TV-type viewer for better
vision in fog and rain, a decelerator indicator that warns the driver behind you
the instant you ease up on the accelerator, a highway condition sensor that gives
notice of ice forming on the pavement, and an audible warning when you drift out
of your lane. Four new solid-state devices - the Gunn oscillator, the LSA diode,
the IMPATT diode, and the TRAPATT diode - promise to make available the cheaper
"Yeah, and I've read that a radar trigger can yield the extra fraction of a second
needed to prevent explosive accelerometer-triggered airbag inflation in an accident,"
Computer-Controlled Autos. "Right," Mac agreed. "You probably
noticed several of the electronic devices mentioned require separate signal processing
and control units. Trevor Jones, head of GM's Electronic Control Systems Group,
considers this duplication wasteful and is doing something about it. That 'something'
is the Alpha series of computer-controlled experimental autos. An automobile computer
such as that in Alpha-1 should, according to Jones, be capable of performing a number
of functions common in a universal control system: add, subtract, remember things,
perform go/no-go logic, and switch. Time sharing in such a computer can justify
its cost by bringing the cost of add-on functions down to a low level.
"For example, in Alpha-1 the computer controls an electronic ignition lock, a
seat belt warning, a 'Phytester,' or drunken driver tester, a digital gas gauge,
a digital speedometer, a digital clock, automatic windshield wipers, headlamp switching,
heater and air-conditioning, turn signals, anti-skid braking control, a fuel economy
computer, electronic fuel injection and ignition, gear shifting, emission monitoring
and control, locking of the doors at 5 mph, and air-bag firing. In addition, many
systems and subsystems are constantly monitored, and any trouble produces a display
that tells the driver what is wrong and what to do about it.
"The digital logic speed is high enough to make control operations appear simultaneous.
For example, quantity of fuel injected and spark timing are calculated for each
cycle, but free intervals remain between these calculations for use by other functions.
Priorities are assigned to all functions, and in an emergency the computer works
from the top of the list so that the most essential override the less important
ones. Air-bag firing, for example, overrides everything else.
"The proliferation of electronic components, however, cannot be permitted to
add to the mile-long rat's nest of wire used in present cars. The answer being built
into Alpha-2 and under development by all three major manufacturers and some independent
firms is the so-called 'one-wire' system. 'One cable' system would be more accurate,
for actually three to six conductors are run in a single cable to all sensors and
all actuators of the car. Information and control signals are multiplexed onto this
cable in the form of serial pulse code modulation (PCM). While all receivers are
exposed to all control signals, only those pulse-coded for a particular receiver
can enter it and initiate the desired action.
"Before the Automotive Central Processor can effectively communicate with all
encode and decode stations throughout the car, two major problems must be overcome:
reliable digital transducers must be developed, and suitable 'muscles' for doing
the actual work must be worked out and subjugated to the electronic controls. We
have good analog transducers, but if a single computer is going to receive and display
information from several transducers, that information must be in digital form.
Analog-to-digital transducers would add an extra step. At present, there are very
few accurate, inexpensive digital transducers. A computer can receive and process
information, but it cannot do major physical work. In a car, such work is usually
done by electricity, hydraulics, or vacuum power. It would seem hydraulic power
possibly generated by the power steering pump, with a fluidics interface between
the electronic control and the powered unit would be the best solution.
"Cars of the future will still require service, and electronics will perform
the diagnostic work. Alpha-1, as already mentioned, does basic troubleshooting with
its on-board computer; but a more elaborate system is already in use by Volkswagen.
Many sensors located throughout every 1972 and later Volkswagen connect to a socket
in the engine compartment. A computer at Volkswagen service stations, when plugged
into this socket, rapidly checks 60 vital points including such things as front
wheel alignment, compression of each cylinder, dwell angle, ignition performance,
generator output, battery water level, and even the condition of the rear window
heater. At the same time the computer prints out in plain English what's right and
wrong with the car. Other manufacturers are likely to follow this lead."
"I'm disappointed," Barney complained. "You've said nothing about a completely
automatic car that drives itself at 100 mph while the owner plays bridge with his
Experimental Alpha-1 auto, by General Motors, uses a digital instrument panel
in front of driver along with the sobriety keyboard located to the right.
These are the components that are used in the electronic ignition system proposed
Mac grinned. "Don't forget I grew up in a garage, and I agree with the auto manufacturers
that the fully automatic car of the Sunday supplements is many years away. Space
engineers who have gone into automobile-engineering have discovered there is one
big difference in the two engineering philosophies: cost! In space, if something
can be done it must be done. In auto manufacturing, you don't do it unless it's
better and at least as cheap. Trevor Jones points out, 'It takes $10,000 just to
insert a new part number in the GM system.' "
"Okay," Barney said, laying down his soldering iron, "but electronics can do
things better and cheaper. With Uncle Sam holding the double-barreled shotgun of
pollution control and energy conservation, and with foreign competition lurking
just outside the church door, the marriage between automobiles and electronics is
going to take place muy pronto."
Posted April 3, 2023
(updated from original post
Mac's Radio Service Shop Episodes on RF Cafe
This series of instructive stories was the brainchild of none other than John T.
Frye, creator of the Carl and Jerry series that ran in
Popular Electronics for many years. "Mac's Radio Service Shop" began life
in April 1948 in Radio News
magazine (which later became Radio & Television News, then
World), and changed its name to simply "Mac's Service Shop" until the final
episode was published in a 1977
Popular Electronics magazine. "Mac" is electronics repair shop owner Mac
McGregor, and Barney Jameson his his eager, if not somewhat naive, technician assistant.
"Lessons" are taught in story format with dialogs between Mac and Barney.