In this arduino interfacing project, you will be learning how to use a seven segment display using Arduino UNO. The main aim is to design a 0 to 9 counter with a 7 segment, Arduino UNO and 74595 shift register.
Seven segment displays consists of seven LEDs arranged in rectangular fashion. Each LED is known as segment. It displays numeric digits which can be HEX or decimal. The LEDs are labelled from a to g. Other LEDs are connected and wired together to form a common pin. Proper forward biasing of the LEDs, will allow some LEDs to light and others in dark displaying the desired character pattern of the number to be generated on the display.
There are two types of seven segment displays - Common cathode and Common Anode. The difference in the displays are that in common cathode displays all the cathodes of the seven segments are connected directly together and all the anodes of the seven segments are connected in the common anodes.
Common Cathode (CC) – In the common cathode display, all the cathode connections of the LED segments are joined together to logic “0” or ground. The individual segments are illuminated by application of a “HIGH”, or logic “1” signal via a current limiting resistor to forward bias the individual Anode terminals (a-g).
Common Anode (CA) – In the common anode display, all the anode connections of the LED segments are joined together to logic “1”. The individual segments are illuminated by applying a ground, logic “0” or “LOW” signal via a suitable current limiting resistor to the Cathode of the particular segment (a-g).
Depending upon the decimal digit to be displayed, the particular set of LEDs is forward biased. To display digit 0, light up six of the LED segments corresponding to a, b, c, d, e and f. The various digits from 0 through 9 can be displayed using a 7-segment display as shown below.
Shift register IC, 74HC595N converts serial data to parallel data. The IC is used here to minimize the use of digital pins of arduino for controlling the seven segment display.
|
SHIFT REGISTER |
ARDUINO |
|
SER |
D2 |
|
SCK |
D3 |
|
SCL |
VCC |
|
RCK |
D4 |
|
GROUND |
GROUND |
|
SHIFT REGISTER |
SEVEN SEGMENT DISPLAY |
|
QA |
7-A |
|
QB |
6-B |
|
QC |
4-C |
|
QD |
2-D |
|
QE |
1-E |
|
QF |
9-F |
|
QG |
10-G |
|
QH |
5-DP |
Inorder to display 0 to 9 using a 7 segment common cathode display, LED segments which have to be illuminated must be made HIGH while others are kept at LOW. For example, inorder to display ‘0’; abcdef must be made high and g is kept at low. Now, the hex value of ‘0’ will be 3F. As shown in the truth table below, each of the hex value must be loaded to the shift register to display digits from 0 to 9.
|
dp |
g |
f |
e |
d |
c |
b |
a |
Hex value |
|
0 |
0 |
1 |
1 |
1 |
1 |
1 |
1 |
0x3F |
|
0 |
0 |
0 |
0 |
0 |
1 |
1 |
0 |
0X06 |
|
0 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
0x5B |
|
0 |
1 |
0 |
0 |
1 |
1 |
1 |
1 |
0x4F |
|
0 |
1 |
1 |
0 |
0 |
1 |
1 |
0 |
0x66 |
|
0 |
1 |
1 |
0 |
1 |
1 |
0 |
1 |
0x6D |
|
0 |
1 |
1 |
1 |
1 |
1 |
0 |
1 |
0x7D |
|
0 |
0 |
0 |
0 |
0 |
1 |
1 |
1 |
0x07 |
|
0 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
0x7F |
|
0 |
1 |
1 |
0 |
1 |
1 |
1 |
1 |
0x6 |
Program file is attached as PDF below....................
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