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Example Ladder Logic Diagram. The schematic diagrams for relay logic circuits are often called line diagrams, because the inputs and outputs are essentially drawn in a series of lines. A relay logic circuit is an electrical network consisting of lines, or rungs, in which each line or rung must have continuity to enable the output device. A ...
A relay allows circuits to be switched by electrical equipment: for example, a timer circuit with a relay could switch power at a preset time. For many years relays were the standard method of controlling industrial electronic systems. A number of relays could be used together to carry out complex functions (relay logic). The principle of relay ...
Part of a ladder diagram, including contacts and coils, compares, timers and monostable multivibrators. Ladder logic is widely used to program PLCs, where sequential control of a process or manufacturing operation is required. Ladder logic is useful for simple but critical control systems or for reworking old hardwired relay circuits. As ...
A solid state relay (SSR) is an electronic switching device that switches on or off when an external voltage (AC or DC) is applied across its control terminals. They serve the same function as an electromechanical relay , but solid-state electronics contain no moving parts and have a longer operational lifetime.
For example, in an induction type electromechanical relay, the time delay for the switching action can be adjusted by adjusting the distance traveled by the disc, whereas in a static relay the delay can be set by adjusting the value of the resistance in an R-C time delay circuit. Static relays may be based on analog solid state circuits ...
A Symbolic Analysis of Relay and Switching Circuits is the title of a master's thesis written by computer science pioneer Claude E. Shannon while attending the Massachusetts Institute of Technology (MIT) in 1937, [1] [2] and then published in 1938.
In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. [ 1 ] : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage , reverse power flow ...
Systems based on relays with low-voltage control circuits permit switching the power to lighting loads from an arbitrary number of locations. For each load, a latching relay is used that mechanically maintains its on- or off-state, even if power to the building is interrupted. Mains power is wired through the relay to the load.