21. Shift Registers and LED

description

Materials

Component	Image
Breadboard
Jumper wires
Arduino Uno R4 Minima
74HC595 Shift Register
LED (white, red, blue, or green)

Instructions

1. Make the following connections using the breadboard and jumper wires.

Power Connections

• Pin 16 of the 74HC595 to 5V.
• Pin 8 of the 74HC595 to the GND.

Control Pin Connections

• Connect Pin 11 (SH_CP) of the 74HC595 to Pin 9 on the Arduino.
• Connect Pin 12 (ST_CP) of the 74HC595 to Pin 11 on the Arduino.
• Connect Pin 14 (DS) of the 74HC595 to Pin 12 on the Arduino.
• Connect Pin 13 (OE) of the 74HC595 to the GND rail.
• Connect Pin 10 (MR) of the 74HC595 to the 5V rail.

LED Connections:

• Connect Pin 15 (Q0) to the anode of the first LED.
• Connect Pin 1 (Q1) to the anode of the second LED.
• Connect Pin 2 (Q2) to the anode of the third LED.
• Connect Pin 3 (Q3) to the anode of the fourth LED.
• Connect Pin 4 (Q4) to the anode of the fifth LED.
• Connect Pin 5 (Q5) to the anode of the sixth LED.
• Connect Pin 6 (Q6) to the anode of the seventh LED.
• Connect Pin 7 (Q7) to the anode of the eighth LED.
• Connect the cathode of each LED to one end of a 220 ohm resistor.
• Connect the other end of each resistor to the GND rail on the breadboard.

2. Paste the following code into your main Arduino sketch:

Code

int tDelay = 100;
int latchPin = 11;  // (11) ST_CP [RCK] on 74HC595
int clockPin = 9;   // (9) SH_CP [SCK] on 74HC595
int dataPin = 12;   // (12) DS [S1] on 74HC595

byte leds = 0;

void updateShiftRegister() {
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, leds);
  digitalWrite(latchPin, HIGH);
}

void setup() {
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
}

void loop() {
  leds = 0;
  updateShiftRegister();
  delay(tDelay);
  for (int i = 0; i < 8; i++) {
    bitSet(leds, i);
    updateShiftRegister();
    delay(tDelay);
  }
}

3. Connect your Arduino to your laptop using a USB-C cable and upload the code to the arduino.

4. Test! Observe the LEDs change sequentially.

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