Published April 12, 2021 © GPL3+

UV Exposure Box

A UV Exposure Box to expose photoresist or solder masks for single and double sided boards.

IntermediateFull instructions provided2 days678

Things used in this project

Hardware components

LED (generic)

5mm Ultraviolet

168

LED (generic)

5mm Red

Microchip ATtiny1614 microprocessor

MAX7219

SOIC

LM1117-5

5V Regulator SOT-223

1N4148 – General Purpose Fast Switching

SOD80C

MMTB2222

SOT-23

Omron G6H-2F Relay

5V DPDT 10Pin SMD

4-Digit 7-Segment CC 0.56in Display

C&K Switches PTS 645 Series Switch

12mm shaft

Passive components

Resistors 0805 SMD - 2 x 22k, 1 x 33k, 2 x 39k, 1 x 1k, 56 x 91R, 18 x 220R, 6 x 330R Capacitors 0805 SMD - 2 x 0.1uF

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)

Story

Most of the projects that I build have a custom printed circuit board. With a preference to making my own PCBs rather than using proto-boards, the minimum track width is usually limited by the method used to make the board. With the Toner method, minimum track width is about 0.016in. To create smaller tracks than this, photographic methods are better suited.

There are a number of tutorials on how to create a board using the photoresist method so I won't cover it here. See DIY PCB Using Liquid Photoresist for one such method.

This project is about creating a UV exposure box to cure the photoresist. I based my design on the LED UV exposure box by Electrobob. The box was built from 40mm x 9mm dressed pine with the top and bottom covered with 3mm MDF. The hinges and clasp was purchased from a local hardware store. The dimensions of the final box is 233mm x 140mm x 86mm.

Homemade UV light box

The circuit

The timer is built around the ATtiny1614 microprocessor. The 4-Digit 7-Segment display is driven by a MAX7219 LED driver. The four switches are connected to a voltage divider which is read by the microprocessor as a analog value. The UV LED lights are switched on via a relay.

Schematic of timer

The LED boards contain 84 Ultraviolet LEDs each. The lower board also contains 66 Red LEDs. There is a micro-switch that closes when the lid is closed. The unit will automatically pause and switch off the UV LEDs when you open the lid to protect your eyesight. The red LEDs switch on when the lid is open so that when creating double-sided boards, the red light will shine through the alignment holes.

Red and UV lights (Note I overrode the lid switch to get the UV lights to illuminate with the lid open)

Building the timer board

With the exception of the switches and display, all components are surface mount components.

Timer PCB uses mostly SMD components

The Eagle files have been included in case you want to get the board commercially made or do as I did and make it yourself. I used the Toner method.

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.

Add the links if your board is single sided.

Add SMD components and links

Next add the headers. If your board has through hole plating, you can solder the wires directly to the board rather than use connectors. On the UPDI header, dab a bit of red paint on the +VE pin since pin headers aren't polarized. This will allow you to know to which end the red wire goes to.

Add Headers

Add the display and buttons.

Add top side compnents

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.

My Homemade UPDI programmer

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

Select the ATtiny1614 board in your IDE

Select Board, chip, clock speed 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.

Using the UV exposure box

From the left, the four switches are MENU, DECREASE, INCREASE, START/STOP

On power on, the last time period that was used will be displayed. If you wish to change it, press the MENU button and the minutes value will flash. Use the INCREASE or DECREASE buttons to set the minutes value. Pressing the MENU button again will allow you set the seconds. Once you have set the seconds, press the MENU button to set the display brightness. Pressing the MENU button for the fourth time will take you back to STOP mode.

After you place the film and PCB on the plate, close the box and press the START/STOP button. The UV lights will come on and the timer will start to count down to zero. Pressing the START/STOP button or opening the lid while the unit is on will turn off the UV lights and pause the timer. Once the timer reaches zero, it will automatically switch off the UV lights.

Code

// UV Light Box
// Based on a light box design by ELECTROBOB (https://www.electrobob.com/uv-exposure-box-part-1-the-box/)
//
// 
// V1: jlb (jbrad2089@gmail.com)
//  - Wrote software for a ATtiny1614 and MAX7219 driving a 4-Digit 7 Segment CC Display
//

/**
 * 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)
 *             +--------+
 */

#include <EEPROM.h>
#include "LedControl.h"
#include "button.h"

//IO Pins
#define MAX7219_DATA 0 //PA4
#define MAX7219_CLK 3  //PA7
#define MAX7219_LOAD 2 //PA6
#define SWITCHES 10    //PA3
#define LEDS 9         //PA2
#define LID 8          //PA1

//LED order 0,7,3,2
int8_t digits[] = {0, 7, 3, 2};

#define SETUP_FLASH_RATE 200;
unsigned long setupTimeout;
bool setupDisplayState = false;

#define COLON_FLASH_RATE 500;
unsigned long colonTimeout;
bool colonDisplayState = false;

uint8_t timerMinutes;
uint8_t timerSeconds;
uint8_t timerBrightness;
bool timerRunning = false;
bool timerUpdated = false;

//EEPROM handling
#define EEPROM_ADDRESS 0
#define EEPROM_MAGIC 0x0BAD0DAD
typedef struct {
  uint32_t magic;
  uint8_t minutes = 0;
  uint8_t seconds = 0;
  uint8_t brightness = 4;
} EEPROM_DATA;

EEPROM_DATA EepromData;       //Current EEPROM settings

enum MenuModesEnum { TIMER, MINUTE_SET, SECOND_SET, BRIGHT_SET };
MenuModesEnum menuMode = TIMER;

LedControl lc=LedControl(MAX7219_DATA,MAX7219_CLK,MAX7219_LOAD,1);

enum buttonEnum { BTN_NONE, BTN_MENU, BTN_UP, BTN_DOWN, BTN_START, BTN_LID };

void menuButtonPressed(void);
void upButtonPressed(void);
void downButtonPressed(void);
void startButtonPressed(void);
void lidButtonRaised(void);

Button* menuButton;
Button* upButton;
Button* downButton;
Button* startButton;
Button* lidButton;

//---------------------------------------------------------------
// Initialise Hardware
void setup() 
{
  pinMode(LEDS, OUTPUT);
  digitalWrite(LEDS, LOW);

  //Eprom
  readEepromData();
  timerRunning = false;
  timerMinutes = EepromData.minutes;
  timerSeconds = EepromData.seconds;
  timerBrightness = EepromData.brightness; 

  //Initialise buttons
  menuButton = new Button(BTN_MENU, SWITCHES, 0, 100, false);
  upButton = new Button(BTN_UP, SWITCHES, 570, 669, false);
  upButton->Repeat(upButtonPressed);
  downButton = new Button(BTN_DOWN, SWITCHES, 460, 569, false);
  downButton->Repeat(downButtonPressed);
  startButton = new Button(BTN_START, SWITCHES, 670, 750, false);
  lidButton = new Button(BTN_LID, LID);
  
  lc.shutdown(0,false);
  lc.setIntensity(0, timerBrightness);              //1 to 15
  lc.clearDisplay(0);

  // Initialize RTC
  while (RTC.STATUS > 0);                           // Wait until registers synchronized
  
  RTC.PER = 1023;                                   // Set period 1 second
  RTC.CLKSEL = RTC_CLKSEL_INT32K_gc;                // 32.768kHz Internal Oscillator  
  RTC.INTCTRL = RTC_OVF_bm;                         // Enable overflow interrupt
  RTC.CTRLA = RTC_PRESCALER_DIV32_gc | RTC_RTCEN_bm;// Prescaler /32 and enable

  //Display current time
  menuMode = TIMER;
  updateDisplay(true);
}

//---------------------------------------------------------------
// RTC Interrupt Handler
ISR(RTC_CNT_vect)
{
  if (timerRunning)
  {
    if (timerSeconds > 0)
    {
      timerSeconds--;
    }
    else if (timerMinutes > 0)
    {
      timerSeconds = 59;
      timerMinutes--;
    }
    timerUpdated = true;
  }
  RTC.INTFLAGS = RTC_OVF_bm;                         // Reset overflow interrupt
}

//---------------------------------------------------------------
// Main program loop
void loop() 
{
  testButtons();

  if (menuMode == TIMER && timerRunning)
  {
    if (millis() > colonTimeout)
    {
      colonDisplayState = !colonDisplayState;
      colonTimeout = millis() + COLON_FLASH_RATE;
      timerUpdated = true;
    }
    if (timerUpdated)
    {
      timerUpdated = false;
      if (timerMinutes == 0 && timerSeconds == 0)
      {
        //Turn off light and stop timer (same as pressing start button to pause)
        startButtonPressed();
      }
      else
      {
        //Display updated time (flashing colon if necessary)
        displayMinutes(timerMinutes, true, colonDisplayState);
        displaySeconds(timerSeconds, true);
      }
    }
  }
  else if (menuMode != TIMER)
  {
    updateDisplay(false);
  }
   
  delay(100);
}

//---------------------------------------------------------------
//Test if any buttons have been pressed
void testButtons()
{
  //Single press buttons
  if (menuButton->Pressed())
  {
    menuButtonPressed();
  }
  if ((lidButton->State() == LOW && timerRunning) || startButton->Pressed())
  {
    //Lid has been openned or start button has been pressed
    startButtonPressed();
  }
  
  //Don't need to check result of pressed since the button handler will invoke its repeat function
  upButton->Pressed();
  downButton->Pressed();
}

//---------------------------------------------------------------
//Handle Menu btton
void menuButtonPressed()
{
  if (menuMode != TIMER || !timerRunning)
  {
    menuMode = (menuMode == BRIGHT_SET) ? TIMER : (MenuModesEnum)((int)menuMode + 1);

    switch (menuMode)
    {
      case MINUTE_SET:
        updateDisplay(false);
        break;

      case SECOND_SET:
        updateDisplay(false);
        break;
        
      case BRIGHT_SET:
        updateDisplay(false);
        break;

      case TIMER:
        //Update EEPROM if any changes
        if (timerMinutes != EepromData.minutes || timerSeconds != EepromData.seconds || timerBrightness != EepromData.brightness)
        {
          EepromData.minutes = timerMinutes;
          EepromData.seconds = timerSeconds;
          EepromData.brightness = timerBrightness; 
          writeEepromData();
        }
        
        //Start in pause mode
        timerRunning = false;
        displayMinutes(timerMinutes, true, true);
        displaySeconds(timerSeconds, true);
        //Now wait for start button
        break;
    }
  }
}

//---------------------------------------------------------------
//Handle Menu btton
void startButtonPressed()
{
  if (menuMode == TIMER)
  {
    if (timerRunning || (timerMinutes == 0 && timerSeconds == 0))
    {
      //Pause the timer
      digitalWrite(LEDS, LOW);
      timerRunning = false;
      displayMinutes(timerMinutes, true, true);
      displaySeconds(timerSeconds, true);
    }
    else if (lidButton->State() != LOW)  //Don't start if lid open
    {
      //Timer runs continiously so just turn on light
      digitalWrite(LEDS, HIGH);
      timerRunning = true;
    }
  }
}

//---------------------------------------------------------------
//Handle DOWN btton
void downButtonPressed()
{
  switch(menuMode)
  {
    case MINUTE_SET:
      timerMinutes = (timerMinutes > 0) ? timerMinutes - 1 : 0; 
      break;
    
    case SECOND_SET: 
      timerSeconds = (timerSeconds > 0) ? timerSeconds - 1 : 0; 
      break;
      
    case BRIGHT_SET: 
      timerBrightness = (timerBrightness > 1) ? timerBrightness - 1 : 1; 
      lc.setIntensity(0, timerBrightness);   //1 to 15
      break;
  }
  updateDisplay(true);
}

//---------------------------------------------------------------
//Handle UP btton
void upButtonPressed()
{
  switch(menuMode)
  {
    case MINUTE_SET:
      timerMinutes = (timerMinutes < 59) ? timerMinutes + 1 : 59; 
      break;
    
    case SECOND_SET: 
      timerSeconds = (timerSeconds < 59) ? timerSeconds + 1 : 59; 
      break;
      
    case BRIGHT_SET: 
      timerBrightness = (timerBrightness < 15) ? timerBrightness + 1 : 15; 
      lc.setIntensity(0, timerBrightness);   //1 to 15
      break;
  }
  updateDisplay(true);
}

//---------------------------------------------------------------
//Flash the value being changed
void updateDisplay(bool force)
{
  setupDisplayState = setupDisplayState | force;
  force = force || (millis() > setupTimeout);
  if (force) 
  {
    setupTimeout = millis() + SETUP_FLASH_RATE;
    bool on = setupDisplayState;
    setupDisplayState = !setupDisplayState;

    if (menuMode == BRIGHT_SET)
    {
      displayBrightness(timerBrightness, on);
    }
    else
    {
      displayMinutes(timerMinutes, on || (menuMode != MINUTE_SET), true);
      displaySeconds(timerSeconds, on || (menuMode != SECOND_SET));
    }
  }
}

//---------------------------------------------------------------
//Show the minutes value
void displayMinutes(uint8_t num, bool on, bool colon)
{
  for (int i = 0; i < 2; i++)
  {
    if (on)
    {
      lc.setDigit(0, digits[i + 2], num % 10, (colon && (i == 0)));
    }
    else
    {
      lc.setChar(0, digits[i + 2], ' ', (colon && (i == 0)));
    }
    num = num / 10;
  }
}

//---------------------------------------------------------------
//Show the seconds value
void displaySeconds(uint8_t num, bool on)
{
  for (int i = 0; i < 2; i++)
  {
    if (on)
    {
      lc.setDigit(0, digits[i], num % 10, false);
    }
    else
    {
      lc.setChar(0, digits[i], ' ', false);
    }
    num = num / 10;
  }
}

//---------------------------------------------------------------
//Show the brightness value
void displayBrightness(uint8_t num, bool on)
{
  //_abc defg
  lc.setRow(0, digits[3], 0x1F);    //b
  lc.setRow(0, digits[2], 0x05);    //r
  
  for (int i = 0; i < 2; i++)
  {
    if (on)
    {
      lc.setDigit(0, digits[i], num % 10, false);
    }
    else
    {
      lc.setChar(0, digits[i], ' ', false);
    }
    num = num / 10;
  }
}

//---------------------------------------------------------------
//Write the EepromData structure to EEPROM
void writeEepromData()
{
  //This function uses EEPROM.update() to perform the write, so does not rewrites the value if it didn't change.
  EEPROM.put(EEPROM_ADDRESS,EepromData);
}

//---------------------------------------------------------------
//Read the EepromData structure from EEPROM, initialise if necessary
void readEepromData()
{
  //Eprom
  EEPROM.get(EEPROM_ADDRESS,EepromData);
  if (EepromData.magic != EEPROM_MAGIC)
  {
    EepromData.magic = EEPROM_MAGIC;
    EepromData.minutes = 0;
    EepromData.seconds = 0;
    EepromData.brightness = 4;
    writeEepromData();
  }
}

/*
Class: Button
Author: John Bradnam (jbrad2089@gmail.com)
Purpose: Arduino library to handle buttons
*/
#pragma once
#include "Arduino.h"

#define DEBOUNCE_DELAY 10

//Repeat speed
#define REPEAT_START_SPEED 500
#define REPEAT_INCREASE_SPEED 50
#define REPEAT_MAX_SPEED 50

class Button
{
	public:
	//Simple constructor
	Button(int pin);
	Button(int name, int pin);
	Button(int name, int pin, int analogLow, int analogHigh, bool activeLow = true);

  //Background function called when in a wait or repeat loop
  void Background(void (*pBackgroundFunction)());
	//Repeat function called when button is pressed
  void Repeat(void (*pRepeatFunction)());
	//Test if button is pressed
	bool IsDown(void);
	//Test whether button is pressed and released
	//Will call repeat function if one is provided
	bool Pressed();
	//Return button state (HIGH or LOW) - LOW = Pressed
	int State();
  //Return button name
  int Name();

	private:
		int _name;
		int _pin;
		bool _range;
		int _low;
		int _high;
		bool _activeLow;
		void (*_repeatCallback)(void);
		void (*_backgroundCallback)(void);
};

/*
Class: Button
Author: John Bradnam (jbrad2089@gmail.com)
Purpose: Arduino library to handle buttons
*/
#include "Button.h"

Button::Button(int pin)
{
  _name = pin;
  _pin = pin;
  _range = false;
  _low = 0;
  _high = 0;
  _backgroundCallback = NULL;
  _repeatCallback = NULL;
  pinMode(_pin, INPUT_PULLUP);
}

Button::Button(int name, int pin)
{
  _name = name;
  _pin = pin;
  _range = false;
  _low = 0;
  _high = 0;
  _backgroundCallback = NULL;
  _repeatCallback = NULL;
  pinMode(_pin, INPUT_PULLUP);
}

Button::Button(int name, int pin, int analogLow, int analogHigh, bool activeLow)
{
  _name = name;
  _pin = pin;
  _range = true;
  _low = analogLow;
  _high = analogHigh;
  _activeLow = activeLow;
  _backgroundCallback = NULL;
  _repeatCallback = NULL;
  pinMode(_pin, INPUT);
}

//Set function to invoke in a delay or repeat loop
void Button::Background(void (*pBackgroundFunction)())
{
  _backgroundCallback = pBackgroundFunction;
}

//Set function to invoke if repeat system required
void Button::Repeat(void (*pRepeatFunction)())
{
  _repeatCallback = pRepeatFunction;
}

  bool Button::IsDown()
{
	if (_range)
	{
		int value = analogRead(_pin);
		return (value >= _low && value < _high);
	}
	else
	{
		return (digitalRead(_pin) == LOW);
	}
}

//Tests if a button is pressed and released
//  returns true if the button was pressed and released
//	if repeat callback supplied, the callback is called while the key is pressed
bool Button::Pressed()
{
  bool pressed = false;
  if (IsDown())
  {
    unsigned long wait = millis() + DEBOUNCE_DELAY;
    while (millis() < wait)
    {
      if (_backgroundCallback != NULL)
      {
        _backgroundCallback();
      }
    }
    if (IsDown())
    {
  	  //Set up for repeat loop
  	  if (_repeatCallback != NULL)
  	  {
  	    _repeatCallback();
  	  }
  	  unsigned long speed = REPEAT_START_SPEED;
  	  unsigned long time = millis() + speed;
      while (IsDown())
      {
        if (_backgroundCallback != NULL)
        {
          _backgroundCallback();
        }
    		if (_repeatCallback != NULL && millis() >= time)
    		{
    		  _repeatCallback();
    		  unsigned long faster = speed - REPEAT_INCREASE_SPEED;
    		  if (faster >= REPEAT_MAX_SPEED)
    		  {
    			  speed = faster;
    		  }
    		  time = millis() + speed;
    		}
      }
      pressed = true;
    }
  }
  return pressed;
}

//Return current button state
int Button::State()
{
	if (_range)
	{
		int value = analogRead(_pin);
		if (_activeLow)
		{
			return (value >= _low && value < _high) ? LOW : HIGH;
		}
		else 
		{
			return (value >= _low && value < _high) ? HIGH : LOW;
		}
	}
	else
	{
		return digitalRead(_pin);
	}
}

//Return current button name
int Button::Name()
{
	return _name;
}

Credits

John Bradnam

141 projects • 167 followers

Thanks to ELECTROBOB.

UV Exposure Box

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

The circuit

Building the timer board

Programming the ATtiny1614

Using the UV exposure box

Schematics

Schematic - Timer

Schematic - LEDs

PCB - Timer

PCB - LEDs

Eagle Files

Code

UV_Light_Box_V1.ino

Button.h

Button.cpp

Credits

John Bradnam

Comments

Embed the widget on your own site

UV Exposure Box

UV Exposure Box

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

The circuit

Building the timer board

Programming the ATtiny1614

Using the UV exposure box

Schematics

Schematic - Timer

Schematic - LEDs

PCB - Timer

PCB - LEDs

Eagle Files

Code

UV_Light_Box_V1.ino

Button.h

Button.cpp

Credits

John Bradnam

Comments

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