Electronic Piggy Bank

Learn to make a glowing electronic piggy bank in this tutorial video using the Adafruit Programmable 1 Coin Acceptor. Code on Github.

Mark and widen some holes with an awl, then use the included machine screws and nuts to secure the faceplate to the front of the house.

Using the pig as a guide, mark where the opening will go, and carefully cut it out with your utility knife. When your pig is all the way inside the house, the two coin slots should line up. Build the rest of the house around the pig and coin acceptor.

I’m also going to add an LCD screen to my piggy bank, and I’m going to use the LCD shield to just sandwich right through the cardboard. So I’m cutting a hole so that the header pins will fit through and sandwich onto the arduino on the other side.

To make my piggy glow, I’m going to use a pink LED. Solder on two pieces of solid wire to make the LED repositionable inside the bank. Use heatshrink tubing for good measure. If you can’t remember which lead is which, use a coincell battery to figure out the positive and negative.

The positive side goes to pin 11 on your arduino, or any of the PWM pins. And the ground goes to ground.

Position the LED so it fits just behind the coin slots, and it’ll shine into the pig. Make a back for the house the same way you made the front, and now it’s time to get to the programming.

You can find the code for this project on github or here:

* connect the COIN wire to digital 2
* set the side switches to "FAST" "NC"

// include the library code:
#include <Wire.h>
#include <Adafruit_MCP23017.h>
#include <Adafruit_RGBLCDShield.h>

// The shield uses the I2C SCL and SDA pins. On classic Arduinos
// this is Analog 4 and 5 so you can't use those for analogRead() anymore
// However, you can connect other I2C sensors to the I2C bus and share
// the I2C bus.
Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();

// These #defines make it easy to set the backlight color
#define RED 0x1
#define YELLOW 0x3
#define GREEN 0x2
#define TEAL 0x6
#define BLUE 0x4
#define VIOLET 0x5
#define WHITE 0x7

// attach coin wire to digital 2
#define COIN 2
int coins;
int brightness = 0;    // how bright the LED is
int fadeAmount = 5;    // how many points to fade the LED by
int fadebrightness = 0;    // how bright the LED is when it's flashing

void setup() {
    // declare pin 11 to be an output for LED:
  pinMode(11, OUTPUT);
  // Debugging output
  // set up the LCD's number of rows and columns:
  lcd.begin(16, 2);

  pinMode(COIN, INPUT);
  digitalWrite(COIN, HIGH); // pull up
  coins = 0;

void loop() {
  lcd.print(" PLEASE INSERT ");
  lcd.print("  ONE QUARTER  ");
    // set the brightness of pin 11:
  analogWrite(11, brightness);

  // while the coin pin is low (no coin detected), do nothing
  while (! digitalRead(COIN)) {

  // while the pin is high, we'll track the length with a counter
  uint8_t counter = 0;
  while (digitalRead(COIN)) {
  Serial.println(" ms long pulse");
  if ((counter > 60) || (counter < 20))
  lcd.print("   OINK OINK! ");
  lcd.print("YOU HAVE $");
  lcd.print("  ");
    // loop through to flash the LED
  fadebrightness = brightness;
  for (int i = brightness; i < 510; i+=5) {
    // turn the pin on:
    analogWrite(11, fadebrightness);
    fadebrightness = fadebrightness + fadeAmount;  
    // reverse the direction of the fading at the ends of the fade: 
    if (fadebrightness == 0 || fadebrightness == 255) {
      fadeAmount = -fadeAmount;
  brightness = brightness + 5;

When you put in a coin, it’ll recognize that and tell you how much money you have in the bank.

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