2 Digit Up/Down Counter Circuit

When buttons on score boards are pressed, digital screens that display the score are generally visible. The 2 Digit Up/Down Counter Circuit is at the heart of this score board. On two 7-segment screens, the two digits are displayed.

I’ll teach you how to make a two-digit up-down counter circuit using an 8051 microcontroller and an ATmega8 microcontroller in this project.

Outline

• 2 Digit Up/Down Counter Circuit Principle
• 2 Digit Up/Down Counter Circuit Diagram
  • Circuit 1: Using 8051 Microcontroller
  • Components Required
  • Circuit 2: Using ATmega8 Microcontroller
  • Components Required
• Circuit Design of 2 Digit 7-Segment Up Down Counter 
• Two Digit Up Down Counter – Circuit Simulation Video
• How to Operate 2 Digit Up Down Counter Circuit?
• Algorithm for Programming
• CODE 
  • Code for 8051 Microcontroller 
  • Code for ATmega8 Microcontroller
• 2 Digit Up Down Counter Circuit using ATmega8 Output
• 2 Digit Up Down Counter Circuit Applications
• Limitations of this Circuit

2 Digit Up Down Counter Circuit Principle

The 2 Digit Up/Down Counter Circuit main idea is to press the button to increment the values on seven segment displays. When button 1 is pressed, the display value is increased by one, and when button 2 is hit, the display value is decremented by one.

Because there are only two displays, the value on the display can be increased and decremented from 0-99. Three screens, i.e. three 7-Segment Displays, should be utilised to display three digits. There are several circuits available for a two-digit up/down counter, however utilising a microcontroller minimises the number of components and board space required, but requires easy programming.Two Digit Up Down Counter Circuit Diagram

Two Digit Up Down Counter Circuit Diagram

Circuit 1: Using 8051 Microcontroller

Components Required

• AT89C51 (8051 Microcontroller)
• 2 X 7-Segment Displays (Common Anode)
• 2 X 2N2222 NPN Transistors
• 3 X Push Buttons
• 2 X 10KΩ Resistors
• 2 X 470Ω Resistors
• 8 X 100Ω Resistors
• 11.0592 MHz Crystal
• 2 X 33pF Capacitor
• 10μF/16V Capacitor
• 1KΩ X 8 Resistor Pack
• Mini Breadboard
• 5V Power Supply
• 8051 Programmer

Circuit 2: Using ATmega8 Microcontroller

Components Required

• ATmega8 Microcontroller
• 2 X 7-Segment Displays (Common Anode)
• 2 X 10KΩ Resistors
• 2 X 330Ω Resistors
• 2 X Push Buttons

Circuit Design of 2 Digit 7-Segment Up Down Counter 

Two seven-segment displays are coupled to the ATMEGA8 microprocessor to make the 2-digit Up/Down counter. Eight pins and one common pin make up the seven segment display.

Seven segment displays are divided into two categories. 1) a shared cathode, and 2) a common anode The type of display utilised here is a typical cathode display. In general, the common pin on common cathode displays should be grounded, while the common pin on common anode displays should be connected to VCC.

Seven segments make up a seven-segment display, which is identical to seven LEDs. These seven segments are represented by seven pins, with the last pin being a dot at the display’s centre. Display attaching logic1 to the segment pin illuminates a specific segment for common cathode. To illuminate the segment in the event of a shared anode, the segment pin should be set to logic0. Each section is given a unique name, beginning with ‘a’ and ending with ‘h’.

In our circuit, seven segment display is connected to micro controller through a current limiting resistor of 330 ohms. Two buttons in pull- down mode are also connected.

The necessity of connecting the buttons in pull down mode is to avoid floating state of the button i.e. unknown state. If the button is connected in pull down mode, this ensures that button is initially in logic0 state.

Two Digit Up Down Counter – Circuit Simulation Video

How to Operate 2 Digit Up Down Counter Circuit?

1. To begin, turn on the circuit.
2. ‘00′ is the value displayed on seven segments.
3. In the circuit, press the 1st button. The value of each of the seven parts is increased by one.
4. Press button 1 one more. On the screens, the value is ’02’.
5. Press the second button now. The value is decrementing to 01 as you can see.
6. The value on the displays can be increased up to 99 times; after that, pressing button 1 will begin incrementing from ‘01′. After decrementing to ’00,’ pressing the second button displays ’00.’ This value can only be altered after it has been increased to at least ‘01′.

Algorithm for Programming

1. Declare the corresponding PORTS of the microcontrollers as input or output.
2. Declare an array with the seven segment codes i.e, if number one is to be displayed, then the binary value that should be passed is as follows:

dp  g  f   e   d   c   b  a
1     1  1   1   1   0   0  1

I’m utilising a Common Anode 7-Segment Display since the b and c segments should be assigned with logic 0 to display ‘1′. As a result, the binary value 0b11111001 or the hexadecimal value 0xf9 is allocated to the port that will show the number 1. The array should be made up of binary or hexadecimal integers ranging from 0 to 9.

3. Check the status of the buttons using if else loop.
4. If the button 1 is pressed for first time, first seven segment (on the left) should display 0 and the other should display 1. So the output is ‘01’.
5. If the button 1 is pressed for second time, value on second button should be incremented by one.
6. If the second button is pressed, value on the first segment should be decremented by one value.

CODE 

	#include<reg51.h>
	#define SEGMENT P0
	sbit switch1=P3^0;
	sbit switch2=P3^1;
	sbit digit1=P2^0;
	sbit digit2=P2^1;
	void delay (int);
	int x=0,y,z;
	unsigned char ch[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x98};
	void delay (int d)
	{
	unsigned char i;
	for(;d>0;d–)
	{
	for(i=250;i>0;i–);
	for(i=248;i>0;i–);
	}
	}
	void main()
	{
	switch1=1;
	switch2=1;
	digit1=1;
	digit2=1;
	while(1)
	{
	if(switch1==0)
	{
	x++;
	delay(200);
	}
	else if(switch2==0)
	{
	x–;
	delay(200);
	}
	y=x/10;
	SEGMENT=ch[y];
	digit1=0;
	delay(10);
	digit1=1;
	z=x%10;
	SEGMENT=ch[z];
	digit2=0;
	delay(10);
	digit2=1;
	}
	}

Code for ATmega8 Microcontroller

	/*
	* updown_counter.c
	* Author: ADMIN
	*/
	/*#define F_CPU 8000000UL*/
	#include <avr/io.h>
	#include <util/delay.h>
	int main(void)
	{
	DDRB = 0x00;
	DDRC = 0xff;
	DDRD = 0xff;
	unsigned int i,x=0,y,z;
	unsigned char arr1[]={0x40,0x79,0x24,0x30,0x19,0x12,0x02,0x78,0x00,0x18};
	while(1)
	{
	if((PINB&0x01)==0x01)
	{
	x++;
	_delay_ms(200);
	}
	else if ((PINB&0x02)==0x02)
	{
	x–;
	_delay_ms(200);
	}
	{
	y=x/10;
	z=x%10;
	PORTC=0x01;
	PORTD=arr1[y];
	_delay_ms(400);
	PORTC=0x02;
	PORTD=arr1[z];
	_delay_ms(800);
	}
	}
	}

2 Digit Up Down Counter Circuit using ATmega8 Output

2 Digit Up Down Counter Circuit Applications

1. This circuit can be used in scoreboards.
2. Up/down counter is used for counting number of objects passed through a point.
3. It is used to count number of persons entering a room.

Limitations of this Circuit

This particular Up/Down Counter circuit is limited to 2 digits i.e. 0-99. If more than 3 digits are required, one should use another display which requires more pins from the controller.