Introduction to relays
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Relays are electromagnetic switches that use a small current to generate a magnetic field, pulling switch contacts together or apart to open and close circuits. They are used to interface control circuits with load circuits, multiply signals, separate DC and AC power, and link information. Relays come in single pole and double pole configurations, with normally open and normally closed contacts that switch state when the coil is energized. Relays allow control of circuits with high voltages or currents using low-power input signals.
Introduction to relays
- 1. A R M I N M A G H A M I INTRODUCTION TO RELAYS
- 2. WHAT ARE RELAYS ? A relay is an electromagnetic switch. A small current flowing through a coil in the relay creates a magnetic field that pulls one switch contact against or away from another. * Interesting Fact : First relays were used in Telegragh circuits. *Sink & Source.
- 3. WHAT ARE RELAYS USED FOR ? i. as interfaces between control circuits and load circuits, ii. for signal multiplication, iii. for separation of direct current and alternating current circuits, iv.linking information
- 4. SCHEMATIC CONFIGURATION OF RELAYS 1 2 4 A2 A1 coil Single Pole Double Throw Double Pole Double Throw single pole (SP) is a single contact (common) where a normally open (NO) and normally closed (NC) relay have a common pole. a double pole (DP) means that each set of contacts has a common terminal ( 1 and 5 ) connected to both an open and a closed set of contacts. When the coil is energized, the circuit between common and NO is closed, and when the coil is de-energized the circuit between common and NC is closed
- 5. FUNCTIONS Number of pins Description 1 2 Normally closed contact 3 4 Normally open contact 5 6 Normally closed contact, time delay 7 8 Normally open contact, time delay 1 2 4 Changeover contact 5 6 8 Changeover contact, time delay A1 A2 The coil terminals (common)
- 6. • Relay contacts are either normally open (NO) or normally closed (NC), The term “normally” refers to the state in which the coil is not energized. Relays can have many independent contacts, some NO and others NC, and each contact can be used in a different circuit for a different task. When the coil is energized, all NO contacts belonging to that relay close, whereas all NC contacts open.
- 8. CHOOSING A RELAY :
- 9. AND ……..
- 10. PROTECTION DIODES FOR RELAYS
- 11. COMPARISONS RELAYS V TRANSISTOR.
- 12. ADVANTAGES :
- 13. DISADVANTAGES
Editor's Notes
- #2: Abstract.