Practical Electronics: Components and Techniques

Chapter 6. Switches

Switches are all around us and have been for the past 150 years or so. Early switches were rather crude things, consisting mainly of one or more blades that could be moved into position between two terminals of some sort using a handle attached to the blade assembly. The old scary movies of the last century used these as set props for locations like Dr. Frankenstein’s lab, and they can also be seen in old photos of Tesla’s and Edison’s actual workshops. In fact, they are still in use and are available for purchase. Figure 6-1 shows a modern version of this ancient switch type.

Figure 6-1. A knife-blade switch

Switches have come a long way since they made their first appearances in the 19th century. They are now available in a vast range of styles and types. Some are incredibly tiny, while others are huge. They can be push activated, sliding, or rotary. Some have a so-called toggle handle to operate them, whereas others have a rocker type of operation. Some are designed to be operated solely by a mechanism, rather than by a human being. Still others have built-in lamps of some sort to let the operator know when a circuit is active or a fault has occurred. A whole industry has grown up around the design and production of switches, and many engineers spend their entire careers designing and testing new types of switches and improving on the designs of older types. ...