Question

In this world of multitasking people do many things while performing other tasks. Think of something where you have to use the Boolean operators AND, OR and NOT. For example, starting a car requires your foot on the brake while turning or pressing the ignition switch. Starting a riding lawn mower requires turning the switch while sitting on the seat. Force is measured and the person must be a certain weight. Discuss three examples incorporating the three (3) Boolean operators. For example, text AND drive, text OR drive, or drive NOT text. Write sample Boolean Equations for each example.

(1) AND logic

(2) OR Logic

(3) NOT logic (inverter)

Based on that

- List the truth table for each

- Please use the scematic symbols for it

- Draw in PLC logic equivalent

Answer 1

(1) AND gate application in car wiper control

Truth Table

X	Y	Z=X.Y
0	0	0
0	1	0
1	0	0
1	1	1

AND gate is utilized to turn the car wipers on which is located on windshield of car when ignition key(I-Switch) AND wiper switches(W-Switch) are ON. We assume that ignition and wiper circuit output is digital in nature, so can be directly connected to two inputs of the AND gate. This concept is shown in diagram below. When we On the Ignition key and also on the wiper switch then on the windshield screen the wiper moves and cleans the glass

.

(2) Or gate application in car ignition system

Truth Table

X	Y	Z=X+Y
0	0	0
0	1	1
1	0	1
1	1	1

Here the two switches X and Y are connected and either Switch X or  Y can be closed in order to put the Ignition on. In other words, any of the switch can be closed or we can say at logic 1 for the ignition to be on.

Then this type of logic gate only produces output when any of the input is present and the output will be true when any of its input is true. The diagram is shown below.

(3) And gate application in fuel level indicator

Truth Table

X	Z=X̄
0	1
1	0

To show whether fuel level in the tank reached the min level, a very simple NOT gate with the digital output level sensor can be utilized.  

Here, when fuel level drops to the minimum level, the sensor gives the output as HIGH. NOT gate gives LOW output then and Red LED glows to show the fuel shortage status. For simulation of the change in the fuel level inside tank, the slider is given

.