7 Segment LED displays are cheap and various sizes available. Unlike ready to use TM1637 7 Segment LED display module, these are slightly difficult to get started. But once the basic is mastered, they are highly flexible. Here is step by step 7 Segment LED display tutorial for dummies on how to light up with battery to control with Arduino without library. 7 Segment LED displays are nothing but exactly like bar graph displays – each segment is a LED. Originally these were vacuum fluorescent displays and that VFDs are still used in good quality electronic stuffs. As for many LEDs together, we can either use a common positive end or a common negative end, there are two types of 7 Segment LED displays –
- Common cathode 7 segment LED display
- Common anode 7 segment LED display
7 Segment LED Display Tutorial For Dummies : By Electrical Connection
That electrical way is widely used for static big displays. Electronic control only added when we need to change the digit to be displays. It is very easy to test a 7 Segment LED Display with battery.
- In common cathode 7 segment LED displays, the 3rd pin will get connected to GND or (-) pole of battery, the intended segment (s) to be listen up will get connected to POWER or (+) pole of battery
- In common anode 7 segment LED displays, the 3rd pin will get connected to POWER or (+) pole of battery, the intended segment (s) to be listen up will get connected to GND or (-) pole of battery
How much power needed (in volts) that depends on the size and specification of the display under question. Usually for displays around 1 inch in size needs 3.3 V as minimum need and 5 V is maximum for them. If you connect them with 9V directly, they will simply die. Obviously you can write 1,2,3,4,5,6,7,8,9,0 by connecting multiple segments.
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7 Segment LED Display Tutorial For Dummies : By Arduino Electronics Connection
There are various electronic ways for controlling these 7 Segment LED Displays. We will programatically control with Arduino. Tis graphics is useful to understand what we told you :
Can you guess from photograph whether we are using common cathode 7 segment LED display or common anode 7 segment LED display? Anode is the positive pole, or negative pole? Is not oxygen get liberated at anode as gas during chemistry’s hydrolysis? In some guides on this earth you’ll see write to connect with -5 volt. Why these are confusing? Why ground, earth, negative voltage, anode making us confused? That thing is discussed in our article on why minus voltage exits. Again another illustration to check whether you do not get confused after you understood :
If you get used with electrical part, wiring and connection will follow the same logic – we can light up multiple LED with Arduino. Obviously common cathode 7 segment LED displays will have difference with common cathode 7 segment LED display in :
- Connecting 3,8 pin of the 7 segment LED display
- Code will be opposite! Which turns on segment of common cathode 7 segment LED display will turn off that segment of common anode 7 segment LED display
We connected :
Arduino Pin 2 with 7 (A)
Arduino Pin 3 with 6 (B)
Arduino Pin 4 with 4 (C)
Arduino Pin 5 with 2 (D)
Arduino Pin 6 with 1 (E)
Arduino Pin 7 with 9 (F)
Arduino Pin 8 with 10 (G)
Arduino Pin 9 with 5 (DP)
Test with this code :
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void setup() { pinMode(2, OUTPUT); pinMode(3, OUTPUT); pinMode(4, OUTPUT); pinMode(5, OUTPUT); pinMode(6, OUTPUT); pinMode(7, OUTPUT); pinMode(8, OUTPUT); pinMode(9, OUTPUT); digitalWrite(9, 1); // "dot" } void loop() { // write '2' digitalWrite(2, 0); digitalWrite(3, 0); digitalWrite(4, 1); digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(7, 0); digitalWrite(8, 0); delay(1000); // write '3' digitalWrite(2, 0); digitalWrite(3, 0); digitalWrite(4, 0); digitalWrite(5, 0); digitalWrite(6, 1); digitalWrite(7, 0); digitalWrite(8, 0); delay(1000); } |
There are zillions of guides on this earth but, in future guides we will add multiple segments – which is called multiplexing using a common IC which Arduino has libraries. So, basically we do not need more than correctly understanding the basic electrical and basic electronics part. Exactly like TM1637 we can make funny animations like scrolling text. That basic when becomes with multi colour tiny LEDs become your computer, mobile phone’s display. Understood?
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