2024-09-09 17:00:03 +01:00
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---
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title: Relays
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tags: [electronics]
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created: Monday, September 09, 2024
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---
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# Relays
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A relay is an electrically operated switch.
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2024-09-09 18:00:03 +01:00
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It uses an electromagnet to mechancially operate a switch. A switch in one
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circuit can be used the trigger the operation of another circuit.
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## Core components
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- electromagnet
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- a coil of wire around an iron core
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- armature
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- a movable magnetic strip
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- contacts
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- electrical connections that can be open or closed
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- spring
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- returns the armature to its resting position when not energised
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## Operation
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Current flows through the electromagnet which creates a magnetic field. This
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field attracts the armature which then moves to open or close the contacts. When
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the current stops, this returns the armature to its original position.
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## Usage
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During the
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[electro-mechanical era of computing](The_History_of_Computing_Swade.md) they
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were used as precursors to vacuum tubes (and later, transistors) to implement
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logic gates. While they were superseded in this domain, they are still used in
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industrial control systems and automobiles.
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