Lesson 6: LCD Display

Put "Hello" and your name on the top line of the LCD and a seconds counter on the bottom line. The knob becomes the contrast control.

One of 7 projects in the Arduino UNO Sensor & Output Starter Kit - LEDs, Buzzer, Servo, Ultras… — the parts below are from that kit.

Before you start

What you build and learn

• How a 16 × 2 character display works
• Wiring a display with 6 signal wires (4-bit mode)
• Setting the contrast with the potentiometer
• setCursor() and print() with the LiquidCrystal library

New words

LCD

Liquid crystal display. This one shows 2 rows of 16 characters.

Contrast

How dark the letters are against the background. Too much and you see solid blocks; too little and you see nothing.

Backlight

The light behind the display. Its pins are 15 (A, +) and 16 (K, −).

Header pins

The row of metal pins that lets the LCD plug into the breadboard.

What this project uses

Every item below is in the kit. Not in the box: Only if your LCD has no pins fitted: a 16-pin header and soldering (adult only).

UNO R3 UNO R3 Development Board ATmega328P Microcontroller with USB Cable, 5V Logic, 14 Digital I/O, 6 Analog Inputs… UNOR3

In the kit

LCD1602 LCD 1602A Character Display Module - 16x2 HD44780 Controller, Blue Backlight, 5V for Arduino & Raspberry Pi D… DIY-211

In the kit

10K potentiometer 10K Ohm Rotary Potentiometer PCB Type - 3-Pin Variable Resistor for Arduino Analog Input & DIY Electronics DIY-220

In the kit

resistor assortment RESISTOR ASSORTED 220-1K-10K DIY-213

In the kit

breadboard 400 Tie Point Solderless Breadboard - Half Size Prototyping Circuit Board with Power Rails, for Arduino & Ele… DIY-238

In the kit

jumper wires Jumper Wire Assorted Pack 120 Pieces - Male-to-Male, Male-to-Female, Female-to-Female 10cm Ribbon Cables for… DIY-212

In the kit

Basics HC-SR04 Ultrasonic Distance Sensor Module for Arduino, Raspberry Pi & DIY Robotics Projects, 5V Trigger/Echo… DIY-00043

In the kit

Build this with

Arduino UNO Sensor & Output Starter Kit - LEDs, Buzzer, Servo, Ultrasonic & LCD

All 10 parts in one box, with this project and 6 more to build from them.

AED 85.00 See the kit Add kit to cart

Need only these parts? Order them loose · from AED 114.74 ▾

Used in this project tick what you still need

UNO R3 UNO R3 Development Board ATmega328P Microcontroller with USB Cable, 5V Logic, 14 Digital I/O, 6 Analog Inputs… UNOR3 · ×1

AED 26.39

In stock

LCD1602 LCD 1602A Character Display Module - 16x2 HD44780 Controller, Blue Backlight, 5V for Arduino & Raspberry Pi D… DIY-211 · ×1

AED 16.83

In stock

10K potentiometer 10K Ohm Rotary Potentiometer PCB Type - 3-Pin Variable Resistor for Arduino Analog Input & DIY Electronics DIY-220 · ×1

AED 10.26

In stock

resistor assortment RESISTOR ASSORTED 220-1K-10K DIY-213 · ×1

AED 9.35

In stock

breadboard 400 Tie Point Solderless Breadboard - Half Size Prototyping Circuit Board with Power Rails, for Arduino & Ele… DIY-238 · ×1

AED 11.58

In stock

jumper wires Jumper Wire Assorted Pack 120 Pieces - Male-to-Male, Male-to-Female, Female-to-Female 10cm Ribbon Cables for… DIY-212 · ×1

AED 25.02

In stock

Also needed untick if you already have them

Basics HC-SR04 Ultrasonic Distance Sensor Module for Arduino, Raspberry Pi & DIY Robotics Projects, 5V Trigger/Echo… DIY-00043 · ×1

AED 15.31

In stock

Selected parts AED 114.74

Add 7 parts to cart

One of each part. Packs (resistor assortment, jumper wires) already hold more than a single build needs. Delivery is AED 20, free on orders AED 100+.

Connections

Unplug USB before you change any wire. Pin names are the labels printed on the board.

Step by step

One thing at a time. Tick nothing off until it matches the diagram.

1. Unplug the USB cable.Watch out: Always unplug the USB cable before you add, move or remove a wire.
2. Look at the LCD: are there 16 metal pins along its top edge?Watch out: If there are only 16 holes, stop here and ask an adult to solder a 16-pin header. Wires just pushed into the holes will not make a reliable connection.
3. Push the LCD into the breadboard so each of its 16 pins is in its own row. Find the small 1 and 16 printed next to the end pins.
4. Wire the power: LCD pin 1 (VSS) to the − rail, pin 2 (VDD) to the + rail and pin 5 (RW) to the − rail.
5. Wire the backlight: LCD pin 15 (A) through a 220 Ω resistor to the + rail, and pin 16 (K) to the − rail.Watch out: Always use the resistor on pin 15.
6. Move the potentiometer's middle wire from A0 to LCD pin 3 (VO). Its outer pins stay on the + and − rails.
7. Wire the six signal pins: LCD 4 (RS) → pin 12, 6 (E) → pin 11, 11 (D4) → pin 10, 12 (D5) → pin 7, 13 (D6) → A1, 14 (D7) → A2. Leave LCD pins 7-10 empty.
8. Plug in USB. The backlight should glow. Turn the knob until you see a row of faint blocks on the top line.Watch out: If the backlight stays dark, unplug and check pins 15 and 16.
9. Upload the Lesson 6 code, then turn the knob slowly until the text is sharp.

Sketch for this project

Written for the board in the kit. Copy it into the Arduino IDE; change the pin numbers if you wire it differently.

/*
  DIY KIT - Arduino UNO Sensor & Output Starter Kit
  Lesson 6 of 7: LCD Display

  WIRING (unplug the USB cable before you wire) - LCD pins are numbered 1-16
    LCD 1 VSS -> GND          LCD 2 VDD -> 5V
    LCD 3 VO  -> potentiometer middle pin (MOVE this wire from A0 - the knob
                 now sets the contrast; outer pins stay on 5V and GND)
    LCD 4 RS  -> pin 12       LCD 5 RW  -> GND       LCD 6 E -> pin 11
    LCD 7-10  -> nothing
    LCD 11 D4 -> pin 10       LCD 12 D5 -> pin 7
    LCD 13 D6 -> pin A1       LCD 14 D7 -> pin A2
    LCD 15 A  -> 220 ohm resistor -> 5V   (backlight +)
    LCD 16 K  -> GND                      (backlight -)

  WHAT SHOULD HAPPEN
    Top line:    Hello, Maker!
    Bottom line: Time:    12 s   (counting up)
    If you see nothing, or only blocks, turn the knob slowly.
*/

#include <LiquidCrystal.h>   // comes with the Arduino IDE - nothing to install

// The pins in this order: RS, E, D4, D5, D6, D7
LiquidCrystal lcd(12, 11, 10, 7, A1, A2);

const char NAME[] = "Maker";               // put your name here (up to 8 letters)
const unsigned long REFRESH_MS = 250;      // redraw 4 times a second
unsigned long lastRefresh = 0;

// Print a number in a fixed width, with spaces in front,
// so "9" does not leave the old "0" of "10" behind.
void printPadded(unsigned long value, int width) {
  String s = String(value);
  while ((int) s.length() < width) s = " " + s;
  lcd.print(s);
}

void setup() {
  lcd.begin(16, 2);          // 16 characters, 2 rows
  lcd.setCursor(0, 0);       // column 0, row 0 = top left
  lcd.print("Hello, ");
  lcd.print(NAME);
  lcd.print("!");
  Serial.begin(9600);
  Serial.println("Lesson 6: LCD Display");
}

void loop() {
  if (millis() - lastRefresh < REFRESH_MS) return;
  lastRefresh = millis();

  unsigned long seconds = millis() / 1000;

  lcd.setCursor(0, 1);       // column 0, row 1 = bottom line
  lcd.print("Time: ");
  printPadded(seconds, 5);
  lcd.print(" s");

  Serial.print("time_s:");
  Serial.println(seconds);
}

Upload it

1. Click Copy (or Download .ino and open the file).
2. In the Arduino IDE choose File → New Sketch, select everything in it and paste.
3. Check the bottom of the window says Arduino Uno and your port (Start here, step 5).
4. Click Upload (the → arrow) and wait for Done uploading.

How the code works

Change it and see

What you should see or hear

• Top line: Hello, Maker!
• Bottom line: Time: and the seconds since start-up, counting up.
• Turning the knob changes how dark the letters are.

If it doesn't work

Small experiment

Turn the knob slowly from one end to the other while the text is showing. Where do the letters disappear, and where do they turn into solid blocks?

Check what you learned

Next

• Lesson 7 uses everything you have wired so far.

Hi DIY KIT, I'm stuck on the Arduino UNO Sensor & Output Starter Kit.
Lesson: __
Step number: __
What should happen: __
What happens instead: __
Error message (copied exactly): __
I'll attach a photo of my wiring.

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