Arduino 7 Segment LED Display and Counter

This is a simple 0 to 9 counter circuit constructed using Arduino! Here, a common cathode 7-segment LED display is connected to Arduino for displaying the digits.
The code (Arduino sketch) allows push button increment of the counter from 0 to 9.
The whole circuit can be powered from a standard 9V PP3/6F22 battery, or from any suitable Arduino power adaptor



                                     

The seven segment display is infact a very simple device. It is a combination of 8 LEDs (the decimal point -DP- is the 8th), which can be arranged so that different combinations can be used to make numerical digits.

Details of a common cathode type 7 segment LED display is shown here. Note that pins 3 and 8 of the display is the cathode terminals.

                                             

Just follow the schematic circuit diagram to make the entire project.
Arduino pins 2, 3, 4, 5, 6, 7 and 8 should go to Display pins 7, 6, 4, 2, 1, 9 and 10 in correct order. In case of any doubt refer this table. Push Switch (S1) input point is at pin 9 of the Arduino.

                                         

Connecting the display pins directly to Arduino I/O pins is not a good practice. For testing purpose only one 330 Ohm resistor (R2) is added between ground rail (0V) and the common cathode pins (3 & 8). It is better to directly connect pins 3 & 8 of the display to ground rail. Next add a 330 Ohm resistor between each of the other connections to the Arduino.

CODE

/* Arduino 7-Segment LED Display for Common Cathode Displays Arduino Pins: 2,3,4,5,6,7,8 Display Pins: 7,6,4,2,1,9,10 Display Pins 3&8 should go to GND Switch Input is at Pin 9 */ byte numbers[10] = { B11111100, B01100000, B11011010, B11110010, B01100110, B10110110, B10111110, B11100000, B11111110, B11100110 }; void setup() { for(int i = 2; i <= 8; i++) { pinMode(i, OUTPUT); } pinMode(9, INPUT); }   int counter = 0; bool go_by_switch = true; int last_input_value = LOW;   void loop() { if(go_by_switch) { int switch_input_value = digitalRead(9); if(last_input_value == LOW && switch_input_value == HIGH) { counter = (counter + 1) % 10; } last_input_value = switch_input_value; } else { delay(500); counter = (counter + 1) % 10; } writeNumber(counter); }   void writeNumber(int number) { if(number < 0 || number > 9) { return; } byte mask = numbers[number]; byte currentPinMask = B10000000; for(int i = 2; i <= 8; i++) { if(mask & currentPinMask) digitalWrite(i,HIGH); else digitalWrite(i,LOW); currentPinMask = currentPinMask >> 1; } }