Archive for the ‘LIGHTING CONTROLS’ Category

A Visit with an Innovator

Monday, May 10th, 2010

A Visit with Lighting Control Pioneer, Lutron Electronics Founder, Joel Spira
On April 28th, I had the privilege of attending an event honoring Joel Spira, founder and chairman of Lutron Electronics. This was a rare chance to meet a pioneer in electrical technology, who was donating artifacts to the Smithsonian National Museum of American History tracing the development of solid-state light dimmers from the early 60s through today. They will be displayed in the collection that includes Thomas Edison’s experimental light bulbs and the first lasers. “Collections such as this one from Lutron help us to understand the continuation of the electrical evolution, the process of invention and the history of business and manufacture,” said Brent D. Glass, director of the museum. “American homes changed significantly during the 20th century as people adopted electricity for any number of tasks, including illumination. Objects such as those being donated by Lutron fit in nicely with the switches and control devices we preserve that date back to Edison’s day. Studying the tools of everyday life, such as light switches, helps us to understand our ever-changing technological society,” said Hal Wallace, associate curator of the museum’s electricity collection. “I am pleased to donate these artifacts to the museum,” said Spira. “For the past 50 years, the solid-state dimmer has made homes more beautiful and offices more efficient—all while saving energy and increasing lamp life.”
The Invention
In 1957 GE had produced a solid-state device called a silicon controlled rectifier (SCR). Two years after that Mr.Spira developed a working model of a light dimmer, which controlled power to incandescent light bulbs using an electronic circuit based on the SCR. In 1961 Joel and Ruth Spira founded Lutron Electronics to manufacture and market the dimmer commercially. In 1962 Mr. Spira was awarded a patent for a home light dimmer.
Engineering Talk
The high point of the day for me was trading some memories of 1960s technology with Mr. Spira. He told me how, while in the Navy during World War II, he learned about hydrogen thyratrons, which were used to generate radar pulses. Hydrogen thyratrons are gas-filled tubes that can be used as high power switches operating in fractions of milliseconds. Since AC power reverses direction 120 times per second, a switch that can operate that quickly can control the power delivered by varying the amount of time during each cycle that the switch conducts. The advantage of this type of control is that power is not wasted when the output is reduced. It’s like turning the light switch off for a small amount of time120 times a second. SCRs are solid state devices that can be used this way. Since thyratrons are physically large, but SCRs are not, this got Mr. Spira thinking about the possibilities. He set out to build a circuit that could control the power fed to an incandescent lamp, but which would be small enough to fit into the space of a home-style light switch. Working in the bedroom of his New York City apartment, he succeeded.
Here we are in 2010 and hydrogen thyratrons are still be used to generate radar pulses, because not only can they switch large electrical currents, they can easily handle the thousands of volts that are required for radar. But Mr. Spira’s original solid-state dimmer has evolved into the preeminent means for controlling lighting systems throughout the world.