# Single Digit Decimal counter using Arduino

“Hello world”,I am not going to start this blog with typical “Hello world” program,since lot of resources already covered Arduino way of telling “hello world”,that is Blinking a LED.

This project is absolutely for beginners who prefers to run than taking a walk,I am going to control 7 segment display to automatically count numbers from 1-9 using Arduino,well I hope you know the basics of 7 segment display.If not,don’t worry here is a concise tutorial about 7 segment display.

lets get started,Here is some components you need before proceeding

1. Arduino (Uno will be cheap)
3. 7 segment display (common anode or cathode)
4. 220ohm resistor – 8 pieces
5. some wire stripes (at least 8 pieces)

In this tutorial I am going to build the project using common anode type 7 segment display but at the end of the post you can find program and schematic for common cathode also.

This is a schematic of this project,Here I have used 7segment display of type common anode.The reason to use series resistors is, LED has a forward voltage of 2V and current 20mA but Arduino has option for providing two voltages 3.3 V and 5 V.So limit the current,You must use resistor otherwise you could end up with burning your 7 segment display.If you are using 5V then (5-2)/0.02= 150 Ohm or higher should be used.

If you are connecting to 3.3 V port you should be using 65 ohm or higher,since (3.3-2/0.02)=65ohm.

Note : This applies for common anode type where you can connect common anode pin to either 3.3V or 5V but for common cathode type you must be using 150ohm or higher valued resistor.

The connection is pretty simple,Just connect pin 1-10 (excluding 3,5,8) to series resistors.First short, pin 3 and 8 os seven segment display,which is to be connected with +5V pin on Arduino.Now connect other end of R1 with Arduino Digital pin 1,Here note that R1 is connected with the pin 1 of seven segment display.

Now similarly connect other series resistor pins to corresponding pins of Arduino.

Note that since we are not going to use pin 5,which is used to display a dot.Also the pin 3 and 8 are connected with 5V,So the corresponding Arduino pins 3 and 8 will also be not used.

If You want to change the pin configuration you need to modify the code as well.

In above code snippet I have defined seven constants which will be defined as INPUT or OUPUT port,later in the program(void setup()).

I have assigned a=7,since the In 7 segment display the segment ‘a’ is connected to pin ‘7’.You can vary this according to your wish but I did like this since you don’t need to remember anything while connecting Arduino pins and 7 segment display.Just connect pin 1 with Arduino pin 1,pin 2 with Arduino pin 2 and so on.

For more detail: Single Digit Decimal

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