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BEX100 – Basic Electricity

BEX100 – Basic Electricity. Electrical Switches. Electrical Switches. Objectives: At the completion of this lesson you will be able to: Explain the difference between the various types of switching devices Explain the operating principles for the various types of switches

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BEX100 – Basic Electricity

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  1. BEX100 – Basic Electricity Electrical Switches

  2. Electrical Switches Objectives: At the completion of this lesson you will be able to: • Explain the difference between the various types of switching devices • Explain the operating principles for the various types of switches • Determine application criteria as it relates to the various switching devices • Properly diagnose problems with switching devices and their related circuits

  3. Electrical Switches Terms To Know: • “SPST” – Single Pole / Single Throw • “SPDT” – Single Pole / Double Throw • Ganged Switch (MPMT) • Mercury Switch • Electromagnetic Switch • Position Switch • Pressure Switch

  4. Electrical Switches Introduction: • Commonly used to control the “on/off function” of a component and/or circuit • Also used to “direct the current” in an electrical circuit • May also be used as “momentary contact” switches • The term “pole(s)” refers to the number of input circuits of the switch • The term “throw(s)” refers to the number of output circuits of the switch • Switches may be “normally open” (NO), or “normally closed” (NC) depending upon the application • May be used on either power or ground side of circuit

  5. Electrical Switches Classifications of Switches

  6. Electrical Switches SPST Switches • Single pole input • Single pole output • A set of contacts inside the switch opens or closes the circuit • The contacts carry the current load of the circuit when closed

  7. Electrical Switches The “Momentary” Switch • A SPST type switch • Switch contacts are spring loaded • Closing the circuit requires overcoming spring pressure • Circuit is opened by spring • Switch is (NO)

  8. Electrical Switches SPDT Switches • One input circuit (pole) • Two output circuits (throws) • Only one output is energized at a time • Contacts carry the current load of circuit

  9. Electrical Switches Ganged Switches (MPMT) • Contain multiple “wipers” that operate in unison • Contacts may carry current load of circuit • Contacts may supply current to an “electromagnetic switch”

  10. Electrical Switches Mercury Switches • A SPST type switch • Uses mercury as the conductor for the contacts • Accurate mounting of mercury switches is essential to proper operation • Used on ground side of circuit

  11. Electrical Switches Electromagnetic Switches • Also called a “relay” • Uses a small amount of current to control a higher amperage circuit • Relays are (NO) type circuits • Often controlled by low amperage switch circuit

  12. Electrical Switches An Electromagnetic Switch in a Horn Circuit

  13. Electrical Switches Position Switches • May be used on power or ground side of circuit • Used to indicate whether a component is in the on or off position • Only provides a “high/low” signal to a solid state control device • A low current circuit

  14. Electrical Switches Pressure Switches • Can be used on either power or ground side of circuit • Switch is turned on/off by “pressure” rather than a component’s movement • Switch may carry current load of circuit • Switch may be used as a type of position switch for a solid state control device

  15. Electrical Switches Switch/Circuit Diagnosis

  16. Switch/Circuit Diagnosis Tools and Methods: • Test Light • Continuity Light • Jumper Wire • DVOM

  17. Switch/Circuit Diagnosis SPST Switches

  18. Switch/Circuit Diagnosis Position Switches / Pressure Switches • Basically a SPST switch • Can be tested using SPST methods • Always refer to appropriate wiring diagrams for the current flow information • It is a good idea to remove the switch from the circuit before testing to prevent accidental damage to solid state components

  19. Switch/Circuit Diagnosis SPST Momentary Switches

  20. Switch/Circuit Diagnosis SPDT Switches

  21. Switch/Circuit Diagnosis “Ganged” / MPMT Switches

  22. Switch/Circuit Diagnosis Mercury Switches

  23. Switch/Circuit Diagnosis Electromagnetic Switches

  24. Elizabethtown Technical CollegeBasic Electricity BEXS100/101Text: Delmar’s Standard Textbook of ElectricityElectrical Switches

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