Atiny85 LED Lander

This is a minimalist 8-LED circuit sculpture built around an ATtiny85 and a 74HC595 shift register, powered by a CR2032 coin cell. It began as a small handheld box design, but I later added lander-style legs to give it a more sculptural presence. Pressing the button cycles through a variety of blinking modes and scrolling LED patterns.

The frame is hand soldered out of 20 AWG brass rods, while the LEDs are vintage round flat-top types sourced from the Ax-Man surplus store in Minneapolis.

At the heart of the display, the 74HC595—an 8-bit shift register—receives data serially and outputs it as eight parallel signals to drive the LEDs.

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Schematic

The capacitors are 0.1 µF, and the value of the current-limiting resistors depends on the LEDs you use—typically ranging from 100 Ω to 220 Ω.

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Firmware

For programming the ATtiny85, I used Pololu's AVR programmer. You can also use an Arduino UNO to act as a programmer instead.

Note: The current button implementation is not ideal—it’s checked at the top of the loop. A more reliable approach would be to use an interrupt-driven button handler.

/*
  Firmware for 8-LED Circuit Sculpture
  ------------------------------------
  This code runs on an ATtiny85 and controls eight LEDs through a 74HC595 shift register.
  A push button cycles through various blinking and scrolling LED patterns. 
  Each pattern is defined as a series of bit sequences, which are shifted out
  to the 74HC595 to illuminate the LEDs in sequence.

  Hardware:
  - ATtiny85 microcontroller
  - 74HC595 8-bit shift register
  - 8 vintage flat-top LEDs
  - CR2032 coin cell power
  - 20 AWG brass frame with push button

  Author: Mohit Bhoite
*/

int latchPin = 1;
int clockPin = 2;
int dataPin = 0;
int outputEnablePin = 0;
int button = 4;

byte data = 0xff;
byte button_count = 0;
byte BCDnumber = 0;

int delay_time = 60;
void setup() 
{
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);  
  pinMode(clockPin, OUTPUT);
  pinMode(button,INPUT_PULLUP);
}

void loop() 
{
  if(digitalRead(button)==0)
  {
    button_count++;
    if(button_count >8) button_count = 0;
    clearLEDs();
    delay(20);
  }
  switch(button_count)
  {
    case 0:
    pattern_0();
    break;
    case 1:
    pattern_1();
    break;
    case 2:
    pattern_2();
    break;
    case 3:
    pattern_3();
    break;
    case 4:
    pattern_4();
    break;
    case 5:
    pattern_5();
    break;
    case 6:
    pattern_6();
    break;
    case 7:
    pattern_7();
    break;
    case 8:
    pattern_8();
    break;
  }
  
}

void pattern_0(void)
{
  BCDnumber++;
  if(BCDnumber>255) BCDnumber = 0;
  updateShiftRegister(BCDnumber);
  delay(200);
}

void pattern_1(void)
{
   updateShiftRegister(0x00);
   delay(200);
   updateShiftRegister(0xff);
   delay(200);
}

void pattern_2(void)
{
   updateShiftRegister(0x0f);
   delay(200);
   updateShiftRegister(0xf0);
   delay(200);  
}

void pattern_3(void)
{
   updateShiftRegister(0b01010101);
   delay(200);
   updateShiftRegister(0b10101010);
   delay(200);  
}

void pattern_4(void)
{
    for (int i = 0; i < 8; i++)
    {
      data = 0;
      bitSet(data,i);
      updateShiftRegister(data);
      delay(delay_time);
    }
}

void pattern_5(void)
{
    for (int i = 7; i > -1; i--)
    {
      data = 0;
      bitSet(data,i);
      updateShiftRegister(data);
      delay(delay_time);
    }
}

void pattern_6(void)
{
  for (int i = 0; i < 8; i++)
    {
      data = 0;
      bitSet(data,i);
      updateShiftRegister(data);
      delay(delay_time);
    }
  for (int i = 7; i > -1; i--)
    {
      data = 0;
      bitSet(data,i);
      updateShiftRegister(data);
      delay(delay_time);
    }
}

void pattern_7(void)
{
  updateShiftRegister(0b10000001);
  delay(delay_time);
  updateShiftRegister(0b01000010);
  delay(delay_time);
  updateShiftRegister(0b00100100);
  delay(delay_time);
  updateShiftRegister(0b00011000);
  delay(delay_time);
  updateShiftRegister(0b00100100);
  delay(delay_time);
  updateShiftRegister(0b01000010);
  delay(delay_time);
}

void pattern_8(void)
{
  updateShiftRegister(0b00011000);
  delay(80);
  updateShiftRegister(0b00100100);
  delay(80);
  updateShiftRegister(0b01000010);
  delay(80);
  updateShiftRegister(0b10000001);
  delay(80);
  updateShiftRegister(0b00000000);
  delay(240);
}

void clearLEDs(void)
{
  updateShiftRegister(0x00);
}

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

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