Electricity and Connectivity – A Railroad Engineer and the Dimmer Switch

Thanks to modern building automation, lighting our homes and businesses today is as easy as setting a schedule and swiping a screen. The amount of control we have now over indoor lighting is unprecedented; we can even dim or brighten a room in incremental amounts using a dial or slide. While the first light switch was patented in Europe, it took American ingenuity to bring it to the next level.

In 1896, railroad engineer and inventor Granville Woods patented the first “Safety Dimmer.” Woods, born a free black man in Cincinatti, Ohio, became a prolific mechanical and electrical engineer in the years after the Civil War. He was self-taught in an era when opportunities for black Americans were scarce. Woods had to drop out of school at the age of ten to help support his family and later trained as a railroad engineer. In fact, one of his most notable inventions is the Synchronous Multiplex Railway Telegraph which allows trains and stations to send messages to one another, improving railway safety and efficiency. Holding some 50 patents for his inventions, Woods even had to defend himself (and win) a patent dispute with Thomas Edison when Edison claimed he had first rights to the telegraphony patent. In an era fraught with racial and political tension, Woods was a pioneer in the fields of science and industry, creating quality inventions to improve the lives of his fellow Americans.

But how did the first dimmer switches work? Woods’ early dimmer switch used a variable resistor, a device which could control the voltage available to a circuit, thereby increasing or decreasing the light output. As helpful as this was, it created a lot of energy loss in the form of heat as the electrical charge moved through the resistor. The dimmer panel would get dangerously hot and was difficult to use, not to mention expensive because of the energy lost.  

Today, instead of diverting energy from the light source to a resistor, modern dimmers rapidly shut the light circuit off and on to reduce the total amount of energy flowing through the circuit—this rapid switching takes place 120 times per second, imperceptible to the naked eye. 

According one source, if every American home installed two dimmer switches, it could save 10 billion kilowatt hours of energy and approximately 1 billion dollars. 

While Woods’ dimmer switch was cumbersome and dangerous due to excessive heat, today we can safely and efficiently adjust the lighting in our homes and offices.

Join us next time as we explore the history of the building control industry and the quality and innovation that characterizes American business and invention, specifically the underestimated genius of a Hollywood bombshell. 

For more information on the KMC Connect and other KMC Controls products, please visit https://www.kmccontrols.com/, your one-stop turnkey solution for building control. We specialize in open, secure, and scalable building automations, teaming up with leading technology providers to create innovative products that help customers increase operating efficiency, optimize energy usage, maximize comfort, and improve safety. Let our Building Geniuses® take your facility to the next level. 










Railroad Picture

Granville Woods Picture

Early Dimmer Switch Picture