Short notes on electronics by Mand Labs

1. www.mandlabs.com

2. Mand Labs presents
Switches

3. Introduction
• Think of switch as an ordinary wire that connects two points
• When two points or terminals get connected, we say “Shorted”
• ON/OFF is a wrong perception
• Various types of switches: One-way, Two-way, 2 terminals, 3
terminals, 6 terminals
• Type of switch defined by Pole and Throw
• Pole is no. of closed circuits in one particular state of switch
• Throw is the total no. of states of switch in which circuits get
closed

4. 2-way switch
• In any state, only two terminals shall be connected at once
(either 1 & 2 or 2 & 3)
• Middle terminal is called COM(Common)

5. Inside a 2-way switch
“Terminals 1 and 2 are shorted”

6. Continuity test of
a 2-way switch
• Rotate meter to beep symbol.
• Connect probes at the first two or last two terminals.
• Observe which two terminals produce a beep.
• Beep indicates “Corresponding terminals are shorted”

7. Continuity Test of a 2-way

8. Flip the switch
“Terminals 2 and 3 are shorted”

9. Continuity Test of
a 2-way contd.

10. Pole and Throw of an SPDT
• No. of throws = 2 (One is upwards and other is downwards)
• In both throws, only one circuit is closed
• Pole = 1 because no. of closed circuits is one in one particular
state of switch
• Throw = 2 since there are two positions in which there are closed
circuits

11. Connecting wire to SPDT
• Use screw driver to lose up the terminals
• Stripped portion of wire must touch the metal contact of switch

12. SPDT Switch Wired
The Wrong WayThe Right Way

13. All terminals wired
Recommended WayOrdinary Way

14. Sample Schematics - 1
• COM terminal is connected toVcc
• Terminal 1 is connected to the anode of an LED

15. Schematics-1 on BB

16. Sample Schematics - 2
• COM terminal is connected to ground
• Terminal 3 is connected to the anode of an LED

17. Schematics-2 on BB

18. Sample Schematics - 3
• COM terminal is connected to the anode of an LED
• Terminal 3 is connected toVcc

19. Schematics-3 on BB

20. Connecting 2 Switches
• Terminal 1 of switch 1 is connected to terminal 1′ of switch 2
• Terminal 3 of switch 1 is connected to terminal 3′ of switch 2

21. Connecting 2 Switches

22. Connecting 2 Switches
• Terminal 1 of switch 1 is connected to terminal 3′ of switch 2
• Terminal 3 of switch 1 is connected to terminal 1′ of switch 2

23. Connecting 2 Switches

24. One-way Switch
• Configurations: ON-OFF, Momentarily ON
• Pole = 1 because there is only closed circuit in one particular state
of switch
• Throw = 1 because there is only state when circuit is closed

25. Tactile Switch
• Momentary Push button
switch
• 4 legs and corresponding
4 terminals
• 2 terminals are shorted
on one side and 2
terminals on the other
• When pressed, all 4
terminals are shorted

26. Understanding Push Switch

27. Schematic Symbol of Push
Switch

28. Internally shorted terminals
• Text imprinted tells about the set
of terminals that are internally
shorted
• Hold the switch in your hand so
that orientation of the text is
either left to right or right to left
• Set of adjacent terminals on LHS
and RHS are internally shorted

29. Internally shorted terminals
• Invert the switch
• See two protruded
lines on two sides
• Terminals on each line
are internally shorted

30. Connecting Push Switch on BB
Text imprinted should run from either left to right or right to left

31. Push Switch on BB
Recommended Way: Connect the push switch across the lower and
the upper halves of the breadboard

32. Micro Switch
• Bump switch
• 3 terminals: COM, NO and NC
• COM: Common, NO: Normally
Open, NC: Normally Closed
• When pressed: COM and NO
gets connected
• In ordinary state: COM and NC
are connected

33. Bump Switch in usual state

34. Bump Switch (when pressed)

35. www.mandlabs.com