• Logic circuits, whether comprised of electromechanical relays or solid-state gates, can be built in many different ways to perform the same functions. There is usually no one “correct” way to design a complex logic circuit, but there are usually ways…

  • The interlock contacts installed in the previous section’s motor control circuit work fine, but the motor will run only as long as each push button switch is held down. If we wanted to keep the motor running even after the…

  • A practical application of switch and relay logic is in control systems where several process conditions have to be met before a piece of equipment is allowed to start. A good example of this is burner control for large combustion…

  • We can construct simple logic functions for our hypothetical lamp circuit, using multiple contacts, and document these circuits quite easily and understandably with additional rungs to our original “ladder.” If we use standard binary notation for the status of the…

  • Ladder diagrams are specialized schematics commonly used to document industrial control logic systems. They are called “ladder” diagrams because they resemble a ladder, with two vertical rails (supply power) and as many “rungs” (horizontal lines) as there are control circuits…

  • As versatile as electromechanical relays can be, they do suffer many limitations. They can be expensive to build, have a limited contact cycle life, take up a lot of room, and switch slowly, compared to modern semiconductor devices. These limitations…

  • A special type of relay is one which monitors the current, voltage, frequency, or any other type of electric power measurement either from a generating source or to a load for the purpose of triggering a circuit breaker to open…

  • What are Time-Delay Relays? Some relays are constructed with a kind of “shock absorber” mechanism attached to the armature which prevents immediate, full motion when the coil is either energized or de-energized. This addition gives the relay the property of…

  • All About Contactors When a relay is used to switch a large amount of electrical power through its contacts, it is designated by a special name: contactor. Contactors typically have multiple contacts, and those contacts are usually (but not always)…

  • An electric current through a conductor will produce a magnetic field at right angles to the direction of electron flow. If that conductor is wrapped into a coil shape, the magnetic field produced will be oriented along the length of…

  • Cyber breaches have become commonplace in today’s world. Cyber-Crime will cost the world $6 trillion annually by 2021. While most businesses anticipate attacks from outsiders, insider threats have proved to be a significant risk too. Case in point, Anthem- a…

  • When a switch is actuated and contacts touch one another under the force of actuation, they are supposed to establish continuity in a single, crisp moment. Unfortunately, though, switches do not exactly achieve this goal. Due to the mass of…

  • Any kind of switch contact can be designed so that the contacts “close” (establish continuity) when actuated, or “open” (interrupt continuity) when actuated. For switches that have a spring-return mechanism in them, the direction that the spring returns it to…

  • A switch can be constructed with any mechanism bringing two conductors into contact with each other in a controlled manner. This can be as simple as allowing two copper wires to touch each other by the motion of a lever,…

  • Though it may seem strange to cover the elementary topic of electrical switches at such a late stage in this book series, I do so because the chapters that follow explore an older realm of digital technology based on mechanical…

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