Living with scarcity did nothing to diminish his burning desire to learn, however. Self-taught, with little formal schooling, he had a gift for discovery. Even as a young boy, he kept a book in which he sketched and described mechanical, chemical and electrical inventions. Despite his lack of education, he became a surveyor, a country school teacher, a superintendent of schools and, from 1876 to 1883, a professor at the State Normal School in Whitewater, Wisconsin.
Colleagues there considered Johnson “one of the most strikingly original teachers.” He taught mathematics, science, drawing and penmanship, but his real passion remained experimentation and invention. In his private laboratory he conducted experiments in many areas, including electro chemistry—a glamour science of the day.
He toiled for three years to invent a device that could control and regulate room temperature and, in 1883, he received his first U.S. patent for the “electric tele-thermoscope.” The mechanism, which would become known as the electric room thermostat, used a sealed bimetal element with one wire of an electrical circuit attached to the fixed end, and the other wire connected to a small pool of mercury in a cup-like reservoir. Changes in air temperature moved the free end of the thermal element into and out of the mercury to close or open the electrical circuit, which in turn controlled his classroom damper in the basement. It was an invention that would launch an industry.
Considered an “intelligent, egotistical, artistic and demanding leader,” Johnson ran the company for 26 years. His passion for invention continued throughout his life, resulting in 50 patents. He died of kidney failure in 1911 while on a trip promoting a custom automobile business that had become part of his namesake company.