LucidTronix is a new Open-Source Electronics designer. We make
tutorials,
as well as transparent, beautiful, and lucid
devices.
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about us here.
7 Segment LED + Shift Register
Display numbers in big bright red LEDs use only 3 micro-controller pins and the 74HC595 shift register
Easily display numbers on a 7-Segment LED Display with this simple breakout board. This PCB uses all easy-to-solder through-hole components. You can
get one at our store
. We use a
74HC595 shift register
to multiplex the Arduino's outputs. Using three control lines: data, clock, and latch, we can control 8 different output pins on the
74HC595 chip
. Bonus feature: we can
daisy-chain
these LED modules and get tons of outputs for those same 3 pins on the atmega.
Lucky Number 7
-
Lucky Number 7Sevens all the way! -
The Naked PCBThe PCB that comes with the kit. -
7 Segment LED Module Being Controlled by Arduino LeonardoArduino powering the 7 Segment numeric LED module. -
Ready To Daisy ChainThese little modules are ready to be daisy chained together giving you as many digits as you need! -
Daisy Chained 7 Segment LEDsDaisy Chain ready! How many numbers you got?! -
Daisy Chainable and Arduino Ready!Grab the code below and start spitting numbers out of your Arduino!
Sevens all the way!
Video of Arduino Controlling the 7 Segment LED Display
Watch the little breakout board in action!
Soldering Video
Watch the 74HC595 shift register and 7-segment LED number display board get assembled and soldered. The actual process takes about 20 minutes but here you can see it happen in one minute.
Step-by-Step Instructions
Step0Get the Kit
First get the kit from
our store
. You can check the parts list below for exact product numbers, but basically what you get is the PCB, a big 7 segment LED display, a 74HC595 shift register, eight 300 ohm resistors, two capacitors, and male and female headers (not shown in the image).
Step1schematic
Positioning is important for board wiring to function correctly. Luckily the manufacturers give us a little U-Shaped depression to show which way is up. See those little squiggly lines on the schematic? Those symbolize the resisters we need for each LED segment.
Step2Insert the Shift Register in the Correct Orientation
Put the 74HC595 shift register into the board as shown in the image. Pin number 1 is the first pin to the left of the U-shaped depression at the top of the chip. Make sure that the U-shape lines up with the silkscreen numer 1 on the PCB.
Step3Grab a Resistor
Grab a resistor from the set of ten and separate it from the rest.
Why do you need 8 resistors for a 7 segment LED?
...The decimal point!
Why do you need 8 resistors for a 7 segment LED?
...The decimal point!
Step4Pinch the Resistor Legs with Pliers
This step is optional, put you may have an easier time slipping the resistor into the board if you first pinch it with pliers.
Step5Insert the Resistor
Insert the resistor into the board. Resistors are symmetric so the orientation doesn't matter.
Step6Insert All the Resistors
Now wash, rinse, and repeat the process with all of the resistors. You can fold the resistors legs out so that they don't fall out of the PCB.
Step7Insert the Headers and the Capacitors
Insert the male and female headers and the capacitors. By convention, we put the male headers on the output side of board, and the female headers on the input side of the board. You can do it either way as long as you are consistent. Now solder everybody down.
Step8Insert The 7 Segment LED in the Correct Orientation
Insert the 7 segment LED in the orientation show in the image. Notice one corner of the LED display is bevelled off, line this corner up with the bottm right corner on the PCB where it says "CORNER" and there is an arrow pointing at it.
Step9Hook it Up to an Arduino
Now you are all set! Hook up your LED board to an Arduino and upload the code we supply below. We connect the data pin (the pin closest to 5V) to the digital pin 2 on the Arduino, the latch pin is connected to the Arduino digital pin 3, and the clock pin is connected to digital pin 4.
Arduino Code to show Numbers on 7 Segment LED Display
One annoying things about getting new 7 Segment LED modules is figuring out which pin goes to which LED-segment. So, the first thing we do in the code is set up the byte array dec_digits:
byte dec_digits[] = {0b11000000,0b11111001,0b10100100,0b10110000,0b10011001,0b10010010,0b10000011,0b11111000,0b,0b10011000 };
Here a zero corresponds to an LED being ON and a 1 corresponds to an LED being OFF. Maybe a little counter-intuitive, but it is this way because the seven segment Display we are using is a common anode device so you toggle the different LEDs on and off by connecting ground to the LED pins. This array contains the LED settings to display the ten decimal digits (thanks
arabic numerals
! Roman numerals are lame...) So, now that we know which bytes we want to send to the shift registers the code just boils down to looping over the byte array and sending out a new byte every so often. This is the code to do that:
for (int numberToDisplay = 0; numberToDisplay < 10; numberToDisplay++) { // take the latchPin low so // the LEDs don't change while you're sending in bits: digitalWrite(latchPin, LOW); // shift out the bits: shiftOut(dataPin, clockPin, MSBFIRST, dec_digits[numberToDisplay]); //take the latch pin high so the LEDs will light up: digitalWrite(latchPin, HIGH); // pause before next value: delay(300); }
Note that in the line:
shiftOut(dataPin, clockPin, MSBFIRST, dec_digits[numberToDisplay]);We grab the LED segment settings from the dec_digits array. We cannot just write the number out to the shift register. For example, if you shift out an 8 you are sending the shift register the byte 00001000, this means light up all of the segment of the 7-Segment LEDs except the third one. This would look like A not an 8. If you want to see an 8 you have to write out the byte: 128 (decimal) = 0x80(hex) = (binary), which means every LED segment on except the decimal point.
Download File
/* LucidTronix 7 Segment LED * and 74HC595 shift register * Tutorial at: * http://www.lucidtronix.com/tutorials/41 */int dataPin = 2;int latchPin = 3;int clockPin = 4;byte dec_digits[] = {0b11000000,0b11111001,0b10100100,0b10110000,0b10011001,0b10010010,0b10000011,0b11111000,0b,0b10011000 };void setup() { //set pins to output so you can control the shift register pinMode(latchPin, OUTPUT); pinMode(clockPin, OUTPUT); pinMode(dataPin, OUTPUT);}void loop() { for (int numberToDisplay = 0; numberToDisplay < 10; numberToDisplay++) { // take the latchPin low so // the LEDs don't change while you're sending in bits: digitalWrite(latchPin, LOW); // shift out the bits: shiftOut(dataPin, clockPin, MSBFIRST, dec_digits[numberToDisplay]); //take the latch pin high so the LEDs will light up: digitalWrite(latchPin, HIGH); // pause before next value: delay(300); }}
Parts
| Title | Description | # | Cost | Link | Picture |
| PCB 7 Segment LED Display and 74HC595 Shift Register | 74HC595 Shift Register breakout board for 7 Segment LED numeric display | 1 | $4.0 | Link |
|
| LED Display | 7 Segment numeric LED Display REDValue:7 Red LEDs | 1 | $0.95 | Link |
|
| Shift Register | IC 8-BIT SHIFT REGISTER 16-DIP Serial to Parallel Tri-State 2 V ~ 6 VValue:74HC | 1 | $0.63 | Link |
|
| Capacitor | Ceramic Capacitors CAP CER 0.1UF 50V 20% RADIALValue: 0.1µF | 2 | $0.24 | Link |
|
| Resistor | RES 300 OHM 1/4W 5% CARBON FILMValue:300 | 8 | $0.08 | Link |
|
Tutorials
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Build your own clock with the MCP79410 chip and 4 7-Segment LED modules....
Connect shift registers together to get more output and input pins from your microcontroller....
A QWERTY keyboard you build yourself....
Standalone programmable Heart-Shaped LED display....
Make an interactive light show using a proximity sensor, and a bunsh of shift registers and LEDs....
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