Author : Khairi
APLICATIONS OF LOGIC GATES
Switch
Light sensor
(LDR)
Street light
STREET LIGHTS
On = 1
Off = 0
Dark = 0
Bright = 1
On = 1
Off = 0
Operational conditions
Author : Khairi
APLICATIONS OF LOGIC GATES
Switch
Light sensor
(LDR)
Street light
STREET LIGHTS
On = 1
Off = 0
Dark = 0
Bright = 1
On = 1
Off = 0
Truth table
Switch LDR Street light
On Dark On
On Bright On
Off Dark On
Off Bright Off
Author : Khairi
APLICATIONS OF LOGIC GATES
SECURITY ALARM
Light sensor
Infrared
sensor
Alarm
(siren)1 0
Operational conditions
Dark = 1
Bright = 0
Off (intruder) = 1
On (no intruder) = 0
On = 1
Off = 0
Author : Khairi
APLICATIONS OF LOGIC GATES
SECURITY ALARM
Light sensor
Infrared
sensor
Alarm
(siren)1 0
Dark = 1
Bright = 0
Off (intruder) = 1
On (no intruder) = 0
On = 1
Off = 0
Truth table
Light
sensor
Infrared
sensorAlarm
Dark Intruder On
Dark No intruder Off
Bright Intruder Off
Bright No intruder Off
Author : Khairi
EXERCISE
Automatic fan control system
Heat detector
LDR
fan
Hot = 1
Cold = 0
Daytime = 1
Night time = 0
On = 1
Off = 0
Construct a truth table for the system above to show the operating
principle of the system
APLICATIONS OF LOGIC GATES
Author : Khairi
Heat TIME FAN
0 0 OFF
0 1 OFF
1 0 OFF
1 1 ON
APLICATIONS OF LOGIC GATES
Automatic fan control system
EXERCISE
Author : Khairi
Fire alarm security system
Heat detector
Smoke detector
siren
Hot = 1
Cold = 0
Smoke = 1
No smoke = 0
On = 1
Off = 0
The system shown is not functioning well.Suggest a modification
in order to make the system works.
USED THE OR GATE
APLICATIONS OF LOGIC GATESEXERCISE
Author : Khairi
a. Complete the truth table below
0
1
1
0
Motor is activate when
some one press any one of
the button
PAST YEARS QUESTION
Author : Khairi
Diagram shows a security system using infrared sensor.
a. If the potential difference across resistor W is 2 V.
What is the potential difference across infrared sensor ?
10 V
b. Component X has a high resistance when the surrounding are dark
and a low resistance in bright surroundings.Name the component X.
Light Dependence Resistor (LDR)
PAST YEARS QUESTION
Author : Khairi
Diagram shows a security system using infrared sensor.
Component S is a switch that connects the 240 V a.c spotlight.
c. Name the component S.
Relay
d. Why is component S necessary in the circuit ?
To switch the spotlight in secondary circuit
PAST YEARS QUESTION
Author : Khairi
0
1
1
1
0
1
Infrared sensor is switch on
when a person crosses the
sensor at night
e. Complete the truth table by using the key given.
0
0
0
1
PAST YEARS QUESTION
Author : Khairi
Infrared sensor is switch on
when a person crosses the
sensor at night
f. Name the correct logic gate for the system.
AND gate
g. Sketch the symbol for the logic gate.
PAST YEARS QUESTION