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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 ...
An optional time delay circuit that controls the timing of the switch action after the input has reached the threshold; A power supply for the static relay circuits; For example, an overcurrent protective relay may have an AC to DC power supply for the input circuit, a level detector circuit and an RC time delay circuit. [1]
Note: In this example, "Run" represents the status of a bit in the PLC, while "Motor" represents the actual output to the real-world relay that closes the motor's real-world circuit. For safety reasons, an emergency stop ("ES") may be hardwired in series with the "Start" switch, and the relay logic should reflect this.
At the time, the methods employed to design logic circuits (for example, contemporary Konrad Zuse's Z1) were ad hoc in nature and lacked the theoretical discipline that Shannon's paper supplied to later projects. Shannon's work also differered significantly in its approach and theoretical framework compared to the work of Akira Nakashima.
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.
Race condition in a logic circuit. Here, ∆t 1 and ∆t 2 represent the propagation delays of the logic elements. When the input value A changes from low to high, the circuit outputs a short spike of duration (∆t 1 + ∆t 2) − ∆t 2 = ∆t 1.
The relay analyzes the resultant A/D converter outputs to determine if action is required under its protection algorithm(s). Protection algorithms are a set of logic equations in part designed by the protection engineer, and in part designed by the relay manufacturer. The relay is capable of applying advanced logic.