The Consumer Electronics Hall of Fame: LiftMaster Garage Door Opener

Some engineers resolved to make garage door openers safe, and they paved the way to industry dominance

5 min read
LiftMaster Garage Door Opener
Heavy Lifting: The LiftMaster 1260 garage door opener can open sectional or one-piece doors and can be installed with basic hand tools, according to its maker.
Photo: Chamberlain Group

The remote-controlled garage door opener was the first major home automation device. Though invented during the Great Depression in the United States, it wasn’t until the 1970s that garage door openers became common in residential use. They almost immediately gained a reputation as a safety hazard, after multiple cases in which young children were struck by descending doors and injured or killed. Not until 1993 did the U.S. government mandate the use of advanced sensors to avert such deaths—a development that paved the way for a single company, LiftMaster, of Oak Brook, Illinois, to dominate the market. Technology originally developed by LiftMaster heavily influenced the development of the standard adopted by the government, and the LiftMaster products compliant with that standard immediately surged in sales.

By then the basic technology was 67 years old. Electric garage door openers were built in 1926 by C.G. Johnson of Hartford City, Indiana, who not coincidentally had invented the segmented overhead garage door four years previously. The first remote-controlled electric garage door openers were built in 1931, by two different teams working independently. In 1954, the Alliance Manufacturing Co., now known as Genie Co., claims to have introduced the first mass-produced, radio-controlled garage door opener. Incidentally, the Overhead Door Co.—which was founded by C.G. Johnson—bought Genie in 1994.

What finally made remote-controlled garage door openers practical for home use in the 1970s was a new approach to mounting garage doors: the split rail, which made it easier to create custom garage doors—important because there were never standards for garage sizes or garage door openings. That innovation opened up opportunities for mass retailers of openers, according to a history of garage door openers published by Genie. Sears, Roebuck and Co., which dominated the do-it-yourself (DIY) market at the time, helped expand the garage door opener market with its decision to resell LiftMaster systems under its renowned Craftsman label.

All along, garage door openers continued to close on people occasionally, particularly children, and pinned them, sometimes fatally. It happened often enough that in 1982, the U.S. government advised that garage door openers should reverse direction if the door struck a solid object. Through the ensuing years, manufacturers devised ways to comply, including the use of force sensors and gauging tension on the chain connecting the motor to the door-opening mechanism.

None of these methods was foolproof, however. Between technology failures and improper installations, garage door openers in the United States from 1982 to 1990 were the cause of countless injuries and 46 deaths, all of them children, according to the U.S. Consumer Product Safety Commission (CPSC).

As early as 1980, engineers had worked out the basics of a system that could prevent such deaths, says Colin Willmott, director of engineering at the Chamberlain Group, which sells garage door openers under four different brand names: LiftMaster, Chamberlain, Merlin, and Grifco. He’s been with the company for 57 years. In an interview, Willmott says that he and his development group took note of the infrared technology that was being used in remote controls for television sets and devised an IR sensor system to detect objects in the way of a closing garage door.

The approach involved mounting an IR emitter a few inches above the ground on either side of the garage door’s frame. If the beam was interrupted at any time while the door was closing, the door opener would be stopped and reversed.

The concept was simple, but the installation was a little beyond the abilities of the average home handyman. It required running wires down both sides of the garage door and careful alignment of the sensors, Willmott explains. The company had also tried using an IR unit on one side and a reflector on the other, but that scheme didn’t work as well, he says. In 1980 all of that was beside the point, anyway: At that time the technology was too expensive and not really reliable, so it was shelved.

Then in 1988, two children, both from the Minneapolis area, were killed in separate garage door accidents on the same day, Willmott recalls. In response, Minnesota lawmakers decided to create stricter safety requirements for garage door openers. Manufacturers were invited to participate. Willmott volunteered the IR system he had devised years earlier. The technology had improved, and the price had come down significantly. The manufacturers voted eight to four to recommend the IR technology for the Minnesota statutes, Willmott says. It’s possible that other manufacturers were amenable to endorsing the use of the IR “electric eye” in part because Willmott had neglected to patent it. Genie, for one, had already “borrowed” the technology, as he wryly puts it.

A few other states, including California, followed Minnesota’s lead, and in 1990 Congress passed the Consumer Product Safety Improvement Act, which required that automatic residential garage door operators conform to the latest version of ANSI 325, which recommended the IR sensors. In 1990 the CPSC issued an advisory that IR sensors were commercially available. In 1993, the act was amended to mandate “electric eyes” or the equivalent.

The 1993 version of the LiftMaster garage door opener, complete with the electric eye, was among the first truly safe remote-controlled garage door openers and easily the best-selling one at the time.

Colin Willmott (foreground) tests the pioneering safety system.Safety First: In 1992, Colin Willmott (foreground) tests the pioneering safety system, based on infrared sensors, that automatically stopped the LiftMaster garage door opener if an object in the door’s path blocked an infrared beam.Photo: Chamberlain Group

“I guess I was the guy responsible for it becoming a state law in Minnesota, and then a federal law. I’ve given a few speeches on the subject and, yeah, I tend to get choked up about it,” Willmott says. “Between 10 to 50 kids were getting injured or killed a year prior to that,” he adds.

The system, still in use today, exploits IR at a wavelength of 930 nanometers, because at that frequency the system very rarely gets fooled by glints of sunlight. The technology is pretty simple. “It’s just a photodiode with an amplifier behind it,” Willmott says. It has barely changed since he and his team first devised it. LiftMaster originally sourced its IR components from Sharp Electronics. It’s now getting its chips from Vishay Intertechnology.

Willmott recalls that the IR components cost about $15 in 1980 and about half that in 1993, when advanced sensors were mandated for garage doors. Nowadays the cost is probably half that again, he says. Semiconductor price reductions have helped Chamberlain keep the prices on its various lines of garage doors steady. In 1980, a garage door opener sold for about $129, Willmott notes, “and you can still buy one for $129.”

In 2015, annual global sales of garage door openers exceeded $1 billion for the first time. LiftMaster still dominates the U.S. market. These days, garage door openers are as likely to be installed by home builders as by homeowners. In 2018, 50 percent of home builders reported installing LiftMaster openers, according to Statista. No one else comes close.

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The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
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A photo of a high-stability film resistor with the letters "MIS" in yellow.
All photos by Eric Schlaepfer & Windell H. Oskay
Blue

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

High-Stability Film Resistor

A photo of a high-stability film resistor with the letters "MIS" in yellow.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

15-Turn Trimmer Potentiometer

A photo of a blue chip
A photo of a blue chip on a circuit board.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Ceramic Disc Capacitor

A cutaway of a Ceramic Disc Capacitor
A photo of a Ceramic Disc Capacitor

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film Capacitor

An image of a cut away of a capacitor
A photo of a green capacitor.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

Dipped Tantalum Capacitor

A photo of a cutaway of a Dipped Tantalum Capacitor

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Axial Inductor

An image of a cutaway of a Axial Inductor
A photo of a collection of cut wires

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

Power Supply Transformer

A photo of a collection of cut wires
A photo of a yellow element on a circuit board.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.

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