Download Switches and Circuit Protectors

Switches and Circuit Protectors
Switch – a device that allows you to “make” or
“break” the connection between two or more
points in a circuit
EGR 101
1
Poles and Throws
Pole – the moving contact
Throw – the non-moving contact
Example: Double-Pole, Single-Throw
(DPST)
EGR 101
2
Normally Open and Normally Closed
Switches
EGR 101
3
Rotary Switches
EGR 101
4
Dual-in-line-Package
(DIP) Switches
8 SPST DIP Switch
Circuit Symbol
EGR 101
5
Fuses
Fuse – a device that is designed to open
automatically if its current exceeds a
specified value
Actual glass fuse
Circuit Symbol
EGR 101
6
Fuse Ratings
Current: the maximum allowable fuse
current before it blows
Voltage: the voltage across an open
fuse that will cause the air in the use to
ionize and allow the open fuse to
conduct.
Fuse ratings are engraved on the metal end caps
EGR 101
7
Types of Fuses
High-Speed
Fast-Blow
Instantaneous
Normal Instantaneous
Time Delay
Slow-Blow
EGR 101
8
Precautions When Replacing Fuses
Make sure all power is removed from the
circuit
Only replace with a fuse of the same current
rating
Only replace with a fuse of the same or
higher voltage rating
Never replace with a fuse with a higher
current rating
EGR 101
9
Micro Fuses
and
Integrated Circuit Protectors
EGR 101
10
Circuit Breakers
Circuit Breakers – not destroyed like
fuses when activated
Single – Pole
Double - Pole
EGR 101
11
GFI (Ground Fault Interrupt)
GFCI (Ground Fault Circuit Interrupt)
Ground Fault Interrupter (GFI) –
common special-case circuit breaker
RESET Button
EGR 101
12