WorldWide Drilling Resource

17 WorldWide Drilling Resource ® DECEMBER 2013 How a Simple Switch Revolutionized Our World by Britt Storkson Owner, P2FlowLLC One can point to several things which could be considered major tech- nological advancements. For example, the invention of the wheel. Another could be the invention of the steam engine. Yet another could be the har- nessing of electrical energy. At the top of this list should be the transistor, a simple electrical switch. Most everyone knows how a mechani- cal switch works. One breaks an elec- trical circuit (disconnects the wiring) with a switch and the current flow to whatever you are running stops; and whatever you are running (a light, motor, heater, etc.) stops. This is fine, except mechanical switches wear out because, obviously, they are mechanical. Also, with induc- tive (magnetic) loads, such as motors, a high-voltage spark is produced when the load is disconnected, eroding the metal contacts. Another limitation is mechanical switches are very slow and are not practical for more than about one on-off cycle per second. The transistor is better. Trans mean- ing moving like “transportation” and istor meaning resistor. A transistor is a “moving (or changing)” resistance. While there are many types of transistors that do many different things, I will use general terms to describe how a transistor works. Most transistors have three termi- nals or connecting points. These are usually tin-plated copper leads soldered to a printed circuit board which routes the current and voltage to wherever it is supposed to go. The leads are called the base, emitter, and collector. With the most common type of tran- sistor, applying a small current (amper- age) to the base of this transistor allows a much larger current to flow between the emitter and collector terminals. When this current is removed the current flow stops...or, more correctly, is reduced to a very small amount. Depending on the current applied to the base terminal, the transistor can present a low resistance between the collector and the emitter so a relatively large current flows...called the “on” state or, with little or no current at the base, can present a high resistance between the collector and emitter where little current flows, which is called the “off” state. While very good, transistors are not perfect as there is some resistance present between the collector and the emitter terminals, even with the best transistors. But they don’t wear out with use and are much faster. Some tran- sistors are able to switch on and off over a billion times per second. They also take heat and cold better, and in most cases are physically much small- er and cheaper to make. The ability of a small current to con- trol the flow of a much larger current is called amplification. This is how a small sound going into a microphone can become a much bigger sound coming out of a speaker. Transistors make it possible. Transistors have thousands of other Storkson cont’d on page 18.