How many TV shows and movies have some mysterious device counting down to zero those displays are 7 segment displays.With the 7 segment displays you can display any number or some alphabets that your heart desires.

At first controlling a 7 segment display seems quite complex but it quickly becomes clear.

What follows is a quick guide to control a 7 segment display with a arduino board

If you want to jump ahead to any other part here's your chance:

Step 1 - What Is A Seven Segment Display?
Step 2 - Parts & Tools
Step 3 - Testing
Step 4 - Built The Circuit
Step 5 - Project 1- One Digit Count Down Timer
Step 6 - Multiplexing
Step 7 - Project 2 - Two Digit Count Down Timer

This instructable is a entry in the arduino contest so if you like it please vote.

Remove these adsRemove these ads by Signing Up

Step 1: What Is A Seven Segment Display?

Picture of What Is A Seven Segment Display?
A seven-segment display (SSD), or seven-segment indicator, is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot-matrix displays. Seven-segment displays are widely used in digital clocks, electronic meters, and other electronic devices for displaying numerical information.A seven segment display, as its name indicates, is composed of seven elements. Individually on or off, they can be combined to produce simplified representations of the arabic numerals.The seven segments are arranged as a rectangle of two vertical segments on each side with one horizontal segment on the top, middle, and bottom. Additionally, the seventh segment bisects the rectangle horizontally. There are also fourteen-segment displays and sixteen-segment displays (for full alphanumerics

Step 2: Parts & Tools

~ 2 x Seven Segment Display (Common Cathode)- Red,Blue
~ 1 x 330 ohm resistor -
~ Arduino Uno(Or equivalent) -
~ Breadboard -
~ Some jumper wires -

~ The arduino programming Environment -
~ USB Cable A-B -
~ Soldering Iron -
~ Solder Wire - Leaded or Lead Free
The total cost should be about 8.10 $ assuming that you have a arduino,breadboard and all the tools
m1s73r2 years ago
Unfortunately I can't test my 7-Segment Display... Your method is not working. I'm using a KINGBRIGHT SA52-11GWA.

I think its a common anode one...

Could you please add a detailed tut on testing these?


@m1s73r All you do is change the the wiring, from Arduino 5V to the anode pins on display and then the pins that are connected to the arduino for anode connects in this guys tutorial become the Cathodes or outputs. You wire no ground. Nothing else changes in wiring. So in the code just change the 1's to 0's. SO short Change the Gnd on this guys tutorial to 5v on arduino and then wire the rest output wires and a few simple code tweeks and done

btrevor4 months ago
How did this happen? Sorry but i don't get it.
{ { 1,1,1,1,1,1,0 }, // = 0
{ 0,1,1,0,0,0,0 }, // = 1
{ 1,1,0,1,1,0,1 }, // = 2
{ 1,1,1,1,0,0,1 }, // = 3
{ 0,1,1,0,0,1,1 }, // = 4
{ 1,0,1,1,0,1,1 }, // = 5
{ 1,0,1,1,1,1,1 }, // = 6
{ 1,1,1,0,0,0,0 }, // = 7
{ 1,1,1,1,1,1,1 }, // = 8
{ 1,1,1,0,0,1,1 } // = 9

these are binary codes to activate lines. o means we have to activate a,b,c,d,e,f so 1,1,1,1,1,1 and g is 0..

AlistairM btrevor4 months ago

its the binary relevant to the seven segment, each 1 turning on a line of the seven seg.

samalert2 years ago
not into electronics seriously but that 1 rupee got me here so see my brothers .... its gud instructable never have i thought tat 7 segment display is so hard .... for u it might be a piece of cake for me its like O_O
the indian rupee is the thing that lead me here too.
me #3
powerman6662 years ago
Ever hooked up a common anode 7 segment display?
I talk about common anode and what to do about it although the process is a bit tedious...if you can only find common anode (like me) then it is worth it.
Bot1398 (author)  powerman6662 years ago
No,but it shouldent be difficult just make all the ones to zeros and all the zeros to ones in the code and you should be ready to go.
What software did you use to create that circuit image? Thank you!
It's called Fritzing...
Applebohn2 years ago
way to copy from wikipedia
rammstein22 years ago
FYI a single 7-segment display can display 126 symbols. ;-)
Wikipedia says 128, actually. Although "symbol" doesn't mean actual LETTER...
no need for wikipedia, simple math: 2^7= 128
Actually, 255 - there is a decimal point - and I don't count all blank as a symbol YMMV
well, de decimal point makes it an eight-segment display i guess. and all blank is a symbol, you can asign a meaning to it as to any other combination. but i think we are leaving math behind and getting too phylosophical...
Oi, I wish this was out about six or seven years. Spent hours if not days just going trial and error trying to figure out how to wire up some of these I mail-ordered. No good online tutorials at the time. I started to have trouble when I wired more than 5 displays together. Random segments would go out. Maybe the current got too low by that point... The lesson I learned from messing with them is, hot-glue is very hard to get off the back, and out of these displays.
dumle292 years ago
As these pictures show, you have chosen wrong resistors. When working with leds with 1 common pin, you should attach a resistor for each individual pin for the LEDs. This is because the more leds you turn on, the more ma the display would require. I know its a pain, but its the correct way.
qwerty1562 years ago
Good Instructables for beginners

Its nice to see someone else my age interested in electronics, even better if they are from india :D