Published October 8, 2021 © GPL3+

Folding Clock

An interesting 3D printed clock that folds out flat or back on top of itself.

AdvancedFull instructions provided16 hours585

Things used in this project

Hardware components

Microchip ATtiny1614 Microprocessor

Real Time Clock (RTC)

SOIC package

TM1650 4-Digit Display Drivers

SOIC 16 package

4-Digit 7-Segment CC 0.8in display

LM1117-5

SOT-223 5V regulator

Passive Components

Resistors: 3 x 10K 0805, Capacitors: 2 x 0.1uF 0805, 1 x 47uF/16V 3528 Tantalum

Tactile Switch, Top Actuated

17mm shaft with button tops

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

3D Printer (generic)

Soldering iron (generic)

Story

Recently I build a Cube clock that showed the time in the same orientation no matter what orientation the clock itself was in. This was inspired by the Lexon Flip Travel Reversible LCD Alarm Clock. One of the other thoughts that I had at the time was a folding clock.

Demonstration of the Folding Clock

Design

This clock was designed based on components that I already had on hand; mainly the two 0.8in 4-Digit 7-Segment clock displays. Since the clock is in two parts, it made more sense to use two 4-Digit, 7-Segment display drivers (TM1650) rather than a single MAX7219 8-Digit 7-Segment display driver.

Most of the electronics are in the bottom or left hand section. Time is controlled by a Real Time Clock chip (DS1307) and it has its own battery so as to not lose any time when the main power supply is disconnected.

Schematic for bottom section.

The top or right hand section contains a mercury switch that determines whether the top section is folded back or is opened out.

Schematic for top section

Setting the time

The clock is configured using three buttons. These are SET, UP and DOWN. The SET button flashes the HOURS, MINUTES and SECONDS values in order. While the value is flashing, the UP and DOWN buttons will either increase or decrease the value respectively. Any changes are written back to the RTC.

You can set the time when the clock is folded back on itself or is fully open.

3D printing

The STL files are included. Either take these to a 3D print shop or if you have your own printer, run them through your slicing software. I used a 0.2mm layer height.

The hinge pin is a piece of 1.75mm filament. I found the hinge started out quite tight but loosen up after opening and closing it a number of times.

The hinge pin is a piece of 1.75mm filament.

The PCB

To minimize the space required, the board has been designed to use Surface Mount Devices (SMD) where possible. Also the boards are designed to be the same size as the 0.8in 4-Digit 7-Segment displays.

When designing the boards, I didn't map the segment pins to their corresponding display pin but rather kept the layout as simple as possible and adjusted for it in the software.

Bottom board - SMD components are used for most of the components

Top board

The Eagle files have been included should you wish to have the board commercially made or you can do as I did and make it yourself. I used the Toner method.

Assembly - Step 1

Start by adding the SMD components. I find it easier to use solder paste rather than use solder from a reel when soldering SMD components. Leave the battery holder off for the time being.

Add the links if you are using a single sided board

Add SMD components and links - Bottom board

Add SMD components and links - Top board

Assembly - Step 2

Add the UPDI programming pin header, the link pin header and the JST power socket to the bottom board.

Add the pin headers and power socket to the bottom board

Add the link pin header to the top board.

Add the pin header to the top board

Note: I usually dab a bit of paint on my connectors to show the correct orientation for any connections that might be made to them.

Assembly - Step 3

Add the mercury switch and display to the top board. (Make sure you don't solder the display in upside down!)

Add the mercury switch and display to the top board

Assembly - Step 4

Now that the pin headers are in place, you can add the battery holder.

Before adding the 32.768Khz watch crystal for the RTC, wrap it in some Kapton tape before soldering it on the copper side of the board. This will ensure that it doesn't short out any tracks underneath.

Glue on the button tops onto the 17mm 6x6mm tactile switches. Take care that the glue doesn't run down the shaft and into the switch. Solder on the switches starting with the middle one first.

Add Battery Holder, Crystal, and switches to the bottom board

Assembly - Step 5

Add the display to the bottom board. (Make sure you don't solder the display in upside down!)

Add the display to the bottom board

Assembly - Step 6

Place the boards into the 3D printed case. Add the DC power socket and wire it to the JST plug. Next feed though a 5 way ribbon link cable through the slots just under the hinge and plug it into the boards.

Add boards to case and wire up power and link cable

After programming, use hot glue to hold the boards in the case.

Use hot glue to hold the boards in the case

Programming the ATtiny1614

The ATtiny1614 is part of the new breed of ATtiny microprocessors. Unlike the earlier series such as the ATtiny85, the new breed use the RESET pin to program the CPU. To program it you need a UPDI programmer. I made one using a Arduino Nano. You can find complete build instructions at Create Your Own UPDI Programmer. It also contains the instructions for adding the megaTinyCore boards to your IDE.

Connect UPDI programmer and upload sketch

Connect the UPDI programmer

Once the board has been installed in the IDE, select it from the Tools menu.

Select board, chip (ATtiny1614), clock speed (20MHz) and the COM port that the Arduino Nano is connected to.

The Programmer needs to be set to jtag2updi (megaTinyCore).

Open the sketch and upload it to the ATtiny1614.

Conclusion

I main issue I have with this clock is the cable that joins the two sections. It really needs to be one of those bendy printed cables that you might find on a CD-ROM drive. The problem is getting one the right length and having the correct sockets so that it can be plugged in.

Overall an interesting project that presented some challenges when designing the code.

Schematics

Code

/**
 * ATtiny1614 Folding Clock
 * John Bradnam (jbrad2089@gmail.com)
 * 
 * 2021-10-08 - Initial Code Base
 *
 * ---------------------------------------
 * ATtiny1614 Pins mapped to Ardunio Pins
 *
 *             +--------+
 *         VCC + 1   14 + GND
 * (SS)  0 PA4 + 2   13 + PA3 10 (SCK)
 *       1 PA5 + 3   12 + PA2 9  (MISO)
 * (DAC) 2 PA6 + 4   11 + PA1 8  (MOSI)
 *       3 PA7 + 5   10 + PA0 11 (UPDI)
 * (RXD) 4 PB3 + 6    9 + PB0 7  (SCL)
 * (TXD) 5 PB2 + 7    8 + PB1 6  (SDA)
 *             +--------+
 *             
 *             
 * BOARD: ATtiny1614/1604/814/804/414/404/214/204
 * Chip: ATtiny1614
 * Clock Speed: 20MHz
 * millis()/micros(): "Enabled (default timer)"
 * Programmer: jtag2updi (megaTinyCore)
 * ----------------------------------------
 */

#include <Wire.h>
#include <RTClib.h>

//DS1307
#define _SCL 9         //PA2
#define _SDA 8         //PA1

#define DATA      0   //PA4
#define CLK1      1   //PA5
#define CLK2      2   //PA6
#define MERCURY   3   //PA7
#define SWITCHES  8   //PA1

#include "Display.h"
#include "Switches.h"

enum STATES { CLOCK_TIME, SET_HOUR, SET_MINUTE, SET_SECOND };
STATES clockState = CLOCK_TIME;

enum FORMATS { HOUR_24, HOUR_12 };
FORMATS clockFormat = HOUR_12;

#define FLASH_TIME 200          //Time in mS to flash digit being set
#define STEP_TIME 350           //Time in mS for auto increment or decrement of time

long flashTimeout = 0;          //Flash timeout when setting clock or alarm
bool flashOn = false;           //Used to flash display when setting clock or alarm
long stepTimeout = 0;           //Set time speed for auto increment or decrement of time

int lastHours = -1;               //Used to test if hour changed
int lastMinutes = -1;             //Used to test if minute changed
int lastSecs = -1;                //Used to test if second changed
int setH = 0;                     //Hour being set
int setM = 0;                     //Minute being set
int setS = 0;                     //Second being set
bool updateTime = true;           //Force display of time

RTC_DS1307 rtc;

void setup() 
{

  setupDisplay();
  setupSwitches();
  
  Wire.usePullups();                // Use pullup resistors on SDA and SCL pins
  if (!rtc.begin())
  {
    //Cannot find RTC
    displayChar(0,CHAR_R);
    displayChar(1,CHAR_T);
    displayChar(2,CHAR_C);
    displayChar(3,SPACE);
    delay(1000);
  }
  else if (!rtc.isrunning()) 
  {
    //RTC lost power - RTC reset;
    rtc.adjust(DateTime(2021, 10, 1, 13, 45, 0));
    displayChar(0,CHAR_L);
    displayChar(1,CHAR_O);
    displayChar(2,5);
    displayChar(3,CHAR_T);
    delay(1000);
  }
}

//----------------------------------------------------------------------
// Main program loop
void loop() 
{
  updateTime |= testSetupButton();
  switch (clockState)
  {
    case CLOCK_TIME: timeMode(); break;
    case SET_HOUR: hourMode(); break;
    case SET_MINUTE: minuteMode(); break;
    case SET_SECOND: secondMode(); break;
  }
}
  
//----------------------------------------------------------------------
// In time display mode
void timeMode()
{
  
  if (clockState == CLOCK_TIME)
  {
    DateTime newTime = rtc.now();
    int hours = newTime.hour();
    int minutes = newTime.minute();
    int secs = newTime.second();
  
    if (updateTime || hours != lastHours || minutes != lastMinutes || secs != lastSecs)
    {
      updateTime = false;
      lastHours = hours;
      lastMinutes = minutes;
      lastSecs = secs;

      bool colon = secs & 0x01;

      switch(clockFormat)
      {
        case HOUR_24: 
          displayTime(HOURS,hours,false,true,colon);
          break;
        
        case HOUR_12: 
          int h = (hours == 0) ? 12 : (hours > 12) ? hours - 12 : hours;
          displayTime(HOURS,h,false,true,colon);
          displayChar(0,(hours < 12) ? CHAR_A : CHAR_P);
          displayChar(1,SPACE);
          break;
      }
      displayTime(MINUTES,minutes,true,true,colon);
      displayTime(SECONDS,secs,true,true,colon);
    }
  }
}

//----------------------------------------------------------------------
// Set hour  mode
void hourMode()
{
  if (millis() > flashTimeout)
  {
    flashTimeout = millis() + FLASH_TIME;
    flashOn = !flashOn;
    displayTime(HOURS, setH, true, flashOn, true);
  }
  if (millis() > stepTimeout)
  {
    if (getButtonState() == UP)
    {
      setH = (setH + 1) % 24;
      displayTime(HOURS, setH, true, flashOn, true);
      stepTimeout = millis() + STEP_TIME;
    }
    else if (getButtonState() == DOWN)
    {
      setH = (setH + 23) % 24;
      displayTime(HOURS, setH, true, flashOn, true);
      stepTimeout = millis() + STEP_TIME;
    }
  }
}

//----------------------------------------------------------------------
// Set minute  mode
void minuteMode()
{
  if (millis() > flashTimeout)
  {
    flashTimeout = millis() + FLASH_TIME;
    flashOn = !flashOn;
    displayTime(MINUTES, setM, true, flashOn, true);
  }
  if (millis() > stepTimeout)
  {
    if (getButtonState() == UP)
    {
      setM = (setM + 1) % 60;
      displayTime(MINUTES, setM, true, flashOn, true);
      stepTimeout = millis() + STEP_TIME;
    }
    else if (getButtonState() == DOWN)
    {
      setM = (setM + 59) % 60;
      displayTime(MINUTES, setM, true, flashOn, true);
      stepTimeout = millis() + STEP_TIME;
    }
  }
}

//----------------------------------------------------------------------
// Set second  mode
void secondMode()
{
  if (millis() > flashTimeout)
  {
    flashTimeout = millis() + FLASH_TIME;
    flashOn = !flashOn;
    displayTime(SECONDS, setS, true, flashOn, true);
  }
  if (millis() > stepTimeout)
  {
    if (getButtonState() == UP)
    {
      setS = (setS + 1) % 60;
      displayTime(SECONDS, setS, true, flashOn, true);
      stepTimeout = millis() + STEP_TIME;
    }
    else if (getButtonState() == DOWN)
    {
      setS = (setS + 59) % 60;
      displayTime(SECONDS, setS, true, flashOn, true);
      stepTimeout = millis() + STEP_TIME;
    }
  }
}

//----------------------------------------------------------------------
// Test for setup button and handle the initial setup
bool testSetupButton()
{ 
  bool updateTime = false; 
  if (getButtonState() == SET)
  {
    delay(10);
    if (getButtonState() == SET)
    {
      DateTime currentTime = rtc.now();
      clockState = (clockState == SET_SECOND) ? CLOCK_TIME : (STATES)((int)clockState + 1);
      switch (clockState)
      {
        case SET_HOUR:
          setH = currentTime.hour();
          setM = currentTime.minute();
          setS = currentTime.second();
          flashTimeout = millis() + FLASH_TIME;
          flashOn = false;
          displayTime(HOURS, setH, true, flashOn, true);
          break;
        
        case SET_MINUTE:
          displayTime(HOURS, setH, true, true, true);
          flashTimeout = millis() + FLASH_TIME;
          flashOn = false;
          displayTime(MINUTES, setM, true, flashOn, true);
          break;
        
        case SET_SECOND:
          displayTime(MINUTES, setM, true, true, true);
          flashTimeout = millis() + FLASH_TIME;
          flashOn = false;
          displayTime(SECONDS, setS, true, flashOn, true);
          break;
        
        case CLOCK_TIME:
          displayTime(SECONDS, setS, true, true, true);
          //Set RTC
          rtc.adjust(DateTime(currentTime.year(), currentTime.month(), currentTime.day(), setH, setM, setS));
          //force update
          updateTime = true;
          break;
      }
      //Wait until button is released
      while (getButtonState())
      {
        delay(10);
      }
    }
  }
  return updateTime;
}

/**
 * ATtiny1614 Folding Clock
 * John Bradnam (jbrad2089@gmail.com)
 * 
 * 2021-10-08 - Create display functions for clock
 *
*/

#pragma once

#include <TM1650.h>

#define DATA      0   //PA4
#define CLK1      1   //PA5
#define CLK2      2   //PA6
#define MERCURY   3   //PA7

#define BRIGHTNESS 2
enum SHOW {HOURS,MINUTES,SECONDS};

#define SPACE 10
#define CHAR_R 11
#define CHAR_T 12
#define CHAR_C 13
#define CHAR_L 14
#define CHAR_O 15
#define CHAR_A 16
#define CHAR_P 17
#define DP_SEGMENT 0b00000010
const PROGMEM byte NUMBER_FONT[] = {
//  edcgfbpa
  0b11101101, // 0
  0b00100100, // 1
  0b11010101, // 2
  0b01110101, // 3
  0b00111100, // 4
  0b01111001, // 5
  0b11111001, // 6
  0b00100101, // 7
  0b11111101, // 8
  0b01111101, // 9
  0b00000000,  // SPACE
  0b10010000, // r
  0b11011000, // t
  0b11010000, // c
  0b11001000, // L
  0b11110000, // o
  0b10111101, // A
  0b10011101  // P
};

//a<->d, f<->c, b<->e
const PROGMEM byte REVERSE_FONT[] = {
//  edcgfbpa
  0b11101101, // 0
  0b10001000, // 1
  0b11010101, // 2
  0b11011001, // 3
  0b10111000, // 4
  0b01111001, // 5
  0b01111101, // 6
  0b11001000, // 7
  0b11111101, // 8
  0b11111001, // 9
  0b00000000,  // SPACE
  0b00010100, // r
  0b00110101, // t
  0b00010101, // c
  0b00100101, // L
  0b00011101, // o
  0b11111100, // A
  0b11110100  // P
};

uint8_t digitsOpen[] = {7,6,5,4,3,2,1,0};
uint8_t digitsClosed[] = {3,2,1,0,4,5,6,7};

//----------------------------------------------------------------------
// TM1650 definitions

TM1650 display1(DATA,   //byte dataPin
                CLK1,   //byte clockPin
                4,      //byte number of digits
                true,   //boolean activeDisplay = true
                BRIGHTNESS       //byte intensity
);

TM1650 display2(DATA,   //byte dataPin
                CLK2,   //byte clockPin
                4,      //byte number of digits
                true,   //boolean activeDisplay = true
                BRIGHTNESS       //byte intensity
);

//-----------------------------------------------------------------------------------
// Forward references

void setupDisplay();
void displayNumber(long num, bool leadingZeros, bool on);
void displayTime(SHOW s, int num, bool leadingZeros, bool on, bool c);
void displayChar(int digit, int chr);
void displayCharWithColon(int digit, int chr, bool c);

//---------------------------------------------------------------
// Setup pin connected to mercury switch
void setupDisplay()
{
  pinMode(MERCURY,INPUT_PULLUP);
}

//---------------------------------------------------------------------
//Write number to display
//  num - (0 to 9999) 
//  leadingZeros - true to have leading zeros
//  on - true to show digit, false to show blank
void displayNumber(long num, bool leadingZeros, bool on)
{
  num = max(min(num, 99999999), 0);
  for (int i = 0; i < 8; i++)
  {
    if (on && (num > 0 || i == 0 || leadingZeros))
    {
      displayChar(i, num % 10);
    }
    else
    {
      displayChar(i, SPACE);
    }
    num = num / 10;
  }
}

//---------------------------------------------------------------------
//Write time to display
//  s - SHOW constant
//  num - (0 to 99) 
//  leadingZeros - true to have leading zeros
//  on - true to show digit, false to show blank
//  c - true to show colon
void displayTime(SHOW s, int num, bool leadingZeros, bool on, bool c)
{
  num = max(min(num, 99), 0);
  int b = (s == SECONDS) ? 2 : (s == HOURS) ? 6 : 4;
  for (int i = 0; i < 2; i++)
  {
    if (on && (num > 0 || i == 0 || leadingZeros))
    {
      displayCharWithColon(b + i, num % 10, c);
    }
    else
    {
      displayChar(b + i, SPACE);
    }
    num = num / 10;
  }
}

//---------------------------------------------------------------------
//Write digit to display
//  digit - digit to write to (0 - left most to 7 - right most)
//  char - character to display
void displayChar(int digit, int chr)
{
  displayCharWithColon(digit, chr, false);
}

//---------------------------------------------------------------------
//Write digit to display
//  digit - digit to write to (0 - left most to 7 - right most)
//  char - character to display
//  c - true to show colon
void displayCharWithColon(int digit, int chr, bool c)
{
  bool open = (digitalRead(MERCURY) == LOW);

  int8_t physical = (open) ? digitsOpen[digit] : digitsClosed[digit];  
  int8_t cDigit = (open) ? 4 : 7;  
  byte segments = (open | (digit < 4)) ? pgm_read_byte(&NUMBER_FONT[chr]) : pgm_read_byte(&REVERSE_FONT[chr]);
  if (c && digit == cDigit)
  {
    segments = segments | DP_SEGMENT;
  }
  if (physical < 4)
  {
    display1.setSegments(segments, physical);
  }
  else
  {
    display2.setSegments(segments, physical - 4);
  }
}

/**
 * ATtiny1614 Folding Clock
 * John Bradnam (jbrad2089@gmail.com)
 * 
 * 2021-10-08 - Create Switch functions for clock
 *
*/

#pragma once

//Switches
#define SWITCHES  8   //PA1

enum BUTTONS { NONE, SET, UP, DOWN };

//-----------------------------------------------------------------------------------
// Forward references

void setupSwitches();
BUTTONS getButtonState();

//---------------------------------------------------------------
// Setup pins connected to switches
void setupSwitches()
{
  pinMode(SWITCHES,INPUT);
}

//-----------------------------------------------------------------------------------
// Return current button state
//  (620 > SET < 800, 450 < DEC < 620, 0 <= INC < 100)
BUTTONS getButtonState()
{
  //S4 (SET) - 0V 0
  //S3 (UP) - 2.5V 512
  //S3 (DOWN) - 3V 614
  BUTTONS result = NONE;
  int value = analogRead(SWITCHES);
  if (value < 100)
  {
    result = UP;
  }
  else if (value < 620)
  {
    result = DOWN;
  }
  else if (value < 800)
  {
    result = SET;
  }
  return result;
}

Credits

John Bradnam

145 projects • 177 followers

Folding Clock

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Design

Setting the time

3D printing

The PCB

Assembly - Step 1

Assembly - Step 2

Assembly - Step 3

Assembly - Step 4

Assembly - Step 5

Assembly - Step 6

Programming the ATtiny1614

Conclusion

Custom parts and enclosures

STL Files

Schematics

Schematic (bottom)

PCB (bottom)

Schematic (top)

PCB (top)

Eagle Files

Code

FoldingClockV1.ino

Display.h

Switches.h

Credits

John Bradnam

Comments

Embed the widget on your own site

Folding Clock

Folding Clock

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Design

Setting the time

3D printing

The PCB

Assembly - Step 1

Assembly - Step 2

Assembly - Step 3

Assembly - Step 4

Assembly - Step 5

Assembly - Step 6

Programming the ATtiny1614

Conclusion

Custom parts and enclosures

STL Files

Schematics

Schematic (bottom)

PCB (bottom)

Schematic (top)

PCB (top)

Eagle Files

Code

FoldingClockV1.ino

Display.h

Switches.h

Credits

John Bradnam

Comments

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