Affordably Lighting the Way
April 20, 2020
Hanging out a shingle is a reference that originated sometime in early 19th century America. The attorneys of the time re-purposed roofing shingles to make signs notifying the public of their newly opened practice. This form of advertisement has worked as signage for businesses and has become an industry of its own today. Almost anywhere we look there are signs of all shapes and sizes vying for our attention.
These visual displays have evolved far beyond those first lowly roofing shingle signs. Electricity enabled lighting of these ads, enhancing their effectiveness. Of course, the electricity powering those lights is not free and minimizing overhead is an important step toward profitability. The technology behind lighted signage has evolved to minimize cost and maximize effectiveness. Tracing the technology’s steps from the thousands of incandescent bulbs that lit the strip in Las Vegas to LED signs Austin is a fascinating journey.
Thomas Edison is frequently credited with inventing the incandescent light bulb. Whoever the inventor, this artificial lighting was a true wonder when it was presented to society in the 1880s. Incandescent bulbs are normally encased in a sealed glass enclosure from which the air has been evacuated. Electric current is passed through a very fine metal wire called a filament inside this vacuum bulb. Tungsten is the most common metal used in filaments. Its small diameter and electrical resistance cause it to heat up and emit visible light very quickly. While effective, most of the electrical energy feeding an incandescent bulb is wasted as heat.
Different scientists began experimenting with evacuated tubes and electricity beginning in the mid-19th century. The fluorescent light bulb emerged and was commercialized by General Electric Company in 1938. This lighting technology relies on the behaviors of different gases when ionized with electric energy. When electrons from the power supply collide with mercury vapor atoms the outermost mercury electron shifts from a lower to a higher energy state and back. When this electron decays to its more stable state it emits an ultraviolet (UV) photon. UV photons then collide with phosphor coatings on the interior wall of a glass tube and emit visible light by luminescence. While more complex than incandescent bulbs, this lighting technology is much more efficient.
Light Emitting Diodes are solid-state semiconductor electronic devices that use very small amounts of current. Somewhat like fluorescent lights, these diodes, when treated with phosphor impurities, emit visible light when current is flowing through them. Recent improvements in this technology have made much brighter and more colorful LED lighting products possible.
The evolution of technologies used to light up signs was made possible by hardworking scientists and inventors. Electric lighting has enabled extended business operations beyond daylight hours. It also made possible the brightly lit signs that lure customers through their front door.
Author: Brent John