Programmable Logic Controller (PLC)

Programmable Logic Controller’s (PLC’s) are small single-purpose computers. They control machines and are common in cars. You probably own more PLC’s than any other type of computer. Today, a single-car has a myriad of PLC’s, usually networked together. PLC’s replace hard-coded wiring, automating tasks.

PLC’s often read input from analog sensors. Responding to temperature, sensing a pedal or a handle, then causing a machine to do something are typical PLC functions.

GM’s automatic transmission was the first application of a PLC. Bedford Associates won a Request for Proposal (RFP) and the lead engineer was Disk Morley.

Besides cars, PLC’s are a common and vital component of modern factories, elevators, and all manner of heavy machinery that repeats the same task.

Because PLC’s are limited in function, they are also typically extremely inexpensive.

Chlorofluorocarbons “Freon”

Freon is the brand name of a Chlorofluorocarbon gas. It replaced other refrigerant chemicals that were more toxic or volatile, including ammonia. Throughout the 20th century, Freon became the dominant refrigerant gas.

The team that invented Freon was led by Thomas Midgley, Jr., who earlier had invented leaded gasoline. It was a joint venture between GM and DuPont, via a company called Kinetic Chemicals.

Eventually, scientists discovered Freon is incredibly environmentally destructive. The US and EU strongly discouraged the use of Freon in the late 1900s. They banned it in 2020. Midgley is arguably responsible for more environmental damage than any other single inventor.

While Freon was toxic to the environment it was largely non-toxic to human beings. There is little doubt that Midgley knew about the problems with lead but it remains less clear if he understood the problems with freon. To demonstrate the non-toxicity of Freon, Midgley once allegedly breathed it in then blew it onto a candle.

Like leaded gasoline, Midgley invented freon at Kettering Laboratories then licensed the patent to Frigidaire, then a division of General Motors.

Tetraethyllead (Leaded Gasoline)

Leaded gasoline prevented engine ping, making driving safer and more pleasant. Correspondingly, it also caused an enormous amount of extremely toxic pollution.

Working for GM under the direct supervision of Charles Kettering at Dayton Research Laboratory, Midgley discovered the benefits of adding lead to gasoline. They named their innovation Tetraethyllead, avoiding any mention of lead, a known toxin.

Eventually, Tetraethyllead leaded gasoline became the standard, with tailpipes emitting poison throughout the world.

Eventually, the catalytic converter enabled lead-free gasoline. Virtually all countries banned Midgley’s leaded gasoline by the mid-1990s and early 2000s.

Speculation remains that the lead pollution had profound health and environmental impact. A substantive decline in violent crime is sometimes attributed to the banning of Midgley’s Tetraethyllead.

Midgley’s lead plant both killed many people and drove others insane.

Midgley also invented CFC’s putting him in the running for the most destructive scientist of all time, short-listed with the likes of Fritz Haber.

Eventually, Midgley died from a pully contraption he invented.

Automatic Automobile Transmission

Automatic transmissions lower the complexity of driving, removing a barrier of entry. They also allow drivers to focus on the road rather than worries about shifting gears. Automatics vastly simplify driving though, in many countries, drivers who take their test with an automatic transmission may only drive using automatic transmission.

Thomas Sturtevant’s automatic transmission system, invented in 1904, used weights and centrifugal force to shift gears. No sooner did he announce it complete than it literally fell apart.

Eventually, Alfred Munro created and patented his system but never commercialized it.

Independent inventor Oscar Banker created the first automatic transmission that worked. No sooner did he announce it perfected than he started a years-long battle with automakers. Eventually, GM purchased his invention. Banker was a serial inventor who also created the inoculation gun and the controls for a helicopter.

Finally, Hydra-Matic became the first commercialized automatic transmission, developed in 1939 General Motors. The Hydra-Matic inventor is unclear and it may be largely from Banker’s system. However, historians disagree about how much, if any, of Banker’s transmission was included in the final design.

Unlike much of the world, 96% of the cars in the United States have automatic transmissions. Manual transmissions are reserved more as a novelty or for racecars.

Automatic transmissions used to be less fuel-efficient than manual transmissions but, thanks largely to computerized shifting, the disparity has all but disappeared. Furthermore, outside of professional racetracks, automatic transmissions accelerate at roughly the same speed as manual transmissions cars.

Due to their design, all known hybrid cars are automatic transmissions. Manual transmission wouldn’t work because the clutch would disengage the engine when the car was supposed to be recapturing energy from momentum. Electric cars do not have gears; the electric motor controls the wheels at any speed. However, this radically different design mimics an automatic transmission.


For centuries ice boxes and ice houses kept food cold in warm weather. Businesses cut the ice into blocks in winter and stored it in underground caverns. Afterward, in warmer months, businesses delivered ice pieces to insulated boxes in homes, “ice boxes,” the original refrigerators.

Early Systems

William Cullen claimed to create the first artificial refrigeration system in 1748. Later, in 1805, Oliver Evans described the first vapor-based refrigeration system in a book. Evans is better known for his automated flour mill and high-pressure steam engine. His colleague, Jacob Perkins built a working refrigeration unit, based on Evans’ designs, decades later. Subsequently, Perkins received a patent in 1835, 30 years after Evans documented the process, leading to a prolonged patent fight.

Early refrigeration systems relied on natural gasses in a closed loop. Basically, vaporization of the gasses and lowered the temperature. The systems were both large, expensive, and highly toxic. In homes, the chemical-based systems were typically installed in basements with pipes leading to a small icebox in the kitchen.

Electric Refrigeration

Fred Wolf created the first self-contained refrigerator in 1913. Branded the DOMestic ELectric REfrigerator, or DOMELRE, it sold thousands of units, proving that branding doesn’t always matter.

In 1914, Nathaniel Wales of Electrolux created a thermostat controlled fridge and eventually branding it Kelvinator, an eventual bestseller.

Alfred Mellowes invented and patented a compact, reasonably priced refrigerator in 1915. Subsequently, William Durant of General Motors purchased the patent and branded the innovation Frigidaire: it became wildly popular.