prime number dedector

 Design a digital circuit that turns on LED when 1, 2, 3, 5, 7, 11, 13 causes on a 4 bit data bus.

              

Here we are going to design a digital circuit that glows an LED when prime numbers till 16 is “ON” on a 4 bit data bus. To design such circuit, the apparatus required are:

APPARATUS:

1.  IC 7408, 7432, 7402.

2.  4 10K Ohm resistor.

3.  9 volt battery.

4.  4 dip switches for input.

5.  1 LED.

STEP 1:

To design a digital circuit, the first thing to do is to make a Truth Table. Following Truth Table will be made in order to achieve our task.

D	C	B	A	Y
0	0	0	0	1
0	0	0	1	1
0	0	1	0	1
0	0	1	1	0
0	1	0	0	1
0	1	0	1	0
0	1	1	0	1
0	1	1	1	0
1	0	0	0	0
1	0	0	1	0
1	0	1	0	1
1	0	1	1	0
1	1	0	0	1
1	1	0	1	0
1	1	1	0	0
1	1	1	1	0

The equation obtained from the above Truth Table is following:

Y= D’.C’.B’.A’+D’.C’.B’.A+D’.C’.B.A’+D’.C.B’.A’+D’.C.B.A’+

D.C’.B.A’+D.C.B’.A’

Now from the above equation we will make a Karnaugh Map.

STEP 2:

The second step is to make a Karnaugh Map so that we can simplify our complicated Boolean Expression. Following Karnaugh Map will take place.

	C’D’	C’D	CD	CD’
A’B’
A’B	1
AB	1	1		1
AB’	1		1	1

From Karnaugh Map, we get the following simplified form of equation:

Y= A.D’+A.B’.C+A.B.C’+B.C’.D’

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7-SEGMENT DISPLAY

7-SEGMENT DISPLAY 

OBJECT:

To design a circuit  that  convert a  8421BCD code into simple decimal and show it on 7 segment display.

COMPONENTS:

1.     Ic74LS147

2.     Ic 7404

3.     Ic 7805

4.     Resister  10K (9)

5.     Resister  150ohm (7)

6.     Push button (9)

7.     7 segment display (1)

8.     9 v battery

ABSTRACT:

We are using dip switches to give input to the encoder IC and then it generates a code of input which is decoded through decoder IC and in the end the seven segment display, displays the number which we had entered.

WORKING:

Logic is useful when the device that you wish to drive uses active-low inputs. Encoders are the opposite of decoders. They are used to generate a coded output from a single active numeric input. To illustrate this in a simple manner, let’s take a look at the simple decimal-to-BCD encoder circuit shown below. In this circuit, normally all lines are held high by the pull-up resistors connected to +5 V. To generate a BCD output that is equivalent to a single selected decimal input, the switch corresponding to that decimal is closed. (The switch acts as an active-low input.)74LS147 decimal-to-BCD (10-line-to-4-line) priority encoder IC. The 74LS147 provides the same basic function but it has active-low outputs. This means that instead of getting an LLHH output when “3” is selected, as in the previous encoder, you get HHLL. The two outputs represent the same thing (“3”); one is expressed in positive true logic, and the other (the 74LS147) is expressed in negative true logic. If you do not like negative true logic, you can slap inverters on the outputs of the 74LS147 to get positive true logic. The choice to use positive or negative true logic really depends on what you are planning to drive. For example, negative true

Multisim Circuit Diagram:

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