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PCB UV Exposure Box

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If you need to speed up prototyping, one way to get some seconds back is to create your own PCB in house. With that, we need some tools to reach our goal. One of those is an UV exposure box. This prequisit will apply to those that don't use a CNC to carve out PCBs. So, I will share my design to any one who is interested.

 

0:40 UV Exposure Enclosure for DIY PCB
18.01.2022

UV Exposure Enclosure for DIY PCB

Ross Robotics

Ross Robotics

UV light enclosure for homemade PCBs. I designed this with common parts to keep cost down. Uses an Arduino, 16x2 LCD, a few basic components. -Set custom duration -Buzzer beeps right before UV LEDs come on and after -Green power LED (Goes off when exposing) -Red LED on while exposing
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I started playing around with photo-sensitive PCBs. So, I needed a device to expose PCBs. It's not just a UV light, we need to control the exposure time and other paramaters. So I used an Arduino for control and to give the user a way to set the time of exposure. In this write-up, I will give you some details on how I did this. Now, you don't need to make this project overly complex and there are ways to simplifiy it. With my own experience, I started with the bare minimum but, I found it a bit, 'lacking.'

I hope you will find this useful and a time saver. I will tell you what worked, what didn't, and any issues I found, and to overcome them.

First, here's the schematic for the entire project. I will post individual schematics of each module to make it easier to follow. The circuit isn't complex and mostly beginner oriented. The code for the Arduino is the complex part but you don't have to understand it as it's complete and is free of bugs (I think).

 

 

Name Quantity Value Description
Wood or Metal Box 1   Any enclosure that meets your needs. Do NOT use plastic!
UV LEDs Multiple   Any type of UV light
Arduino 1   Any compatible Arduino board
U1 1   16x2 LCD
Start,Min,Sec,Reset 4   Momentary Push buttons for program control
D1 1   Green LED for power indication
D2 1   Red LED for exposure indication
POT 1 10K Potentiometer for LCD contrast
R1-R8 Multiple 1K Resistors for current limiting and button pull downs.
T1 Mulitple PNP Transistors to drive LEDs.  Any PNP that can handle 100mA+ current

 

#include <LiquidCrystal.h>
#include <stdio.h>

const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

int minutes = 0;
int seconds = 0;
int countdown = 0;
const int startButton = 2;
const int resetButton = 5;
const int minutesButton = 3;
const int secondsButton = 4;
const int LED_UV = 6;
const int UV_BRD1 = 16;
const int UV_BRD2 = 17;
const int buzzerPin = 7;
const int pwrLED = 14;
const int expLED = 15;
boolean startCountdown = false;
int logic1, logic2, logic3, logic4;

void setup(){
  pinMode(startButton, INPUT_PULLUP);
  pinMode(resetButton, INPUT_PULLUP);
  pinMode(minutesButton, INPUT_PULLUP);
  pinMode(secondsButton, INPUT_PULLUP);
  pinMode(pwrLED, OUTPUT);
  pinMode(expLED, OUTPUT);
  pinMode(LED_UV, OUTPUT);
  pinMode(UV_BRD1, OUTPUT);
  pinMode(UV_BRD2, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  lcd.begin(16, 2);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("-Exposure Time-");
  lcd.setCursor(0, 1);
  lcd.print("- Press SETUP -");
  digitalWrite(LED_UV, LOW);
  digitalWrite(pwrLED, HIGH);
  Serial.begin(9600);
}

void splashscreen(){
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(" Exposure Time");
  lcd.setCursor(0, 1);
  lcd.print("* Press Start *");
}

void buzzer(){
  for (int x = 0; x <= 3; x++)
  {
    tone(buzzerPin, 1500, 100);
    delay(200);
    tone(buzzerPin, 1500, 100);
    delay(200);
    tone(buzzerPin, 1500, 100);
    delay(200);
    tone(buzzerPin, 1500, 100);
    delay(200);
  }
}

void uberTime(){
  countdown = ((minutes * 60) + seconds);
  digitalWrite(LED_UV, HIGH);
  digitalWrite(UV_BRD1, HIGH);
  digitalWrite(UV_BRD2, HIGH);
  digitalWrite(expLED, HIGH);
  digitalWrite(pwrLED, LOW);

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Exposing Board");
  lcd.setCursor(0, 1);
  lcd.print("Time:");
  lcd.setCursor(11, 1);
  lcd.print(" Secs");
  for (int timer = countdown; timer >= 0; timer --){
    char buffer[6];

    sprintf(buffer, "%4d", countdown);
    lcd.setCursor(7, 1);
    lcd.print(buffer);
    delay(1000);
    countdown = countdown - 1;
  }

  digitalWrite(LED_UV, LOW);
  digitalWrite(UV_BRD1, LOW);
  digitalWrite(UV_BRD2, LOW);
  digitalWrite(expLED, LOW);
  digitalWrite(pwrLED, HIGH);

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(" ** ALL DONE **");
  lcd.setCursor(0, 1);
  lcd.print("  Press START");
  buzzer();

  logic1 = digitalRead(startButton);
  while (logic1 != 0){
    logic1 = digitalRead(startButton);
  }

  startCountdown = false;
  minutes = 0;
  seconds = 0;
  countdown = 0;
}

void setupTimer(){
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("  - Set Time -  ");
  lcd.setCursor(0, 1);
  lcd.print("Then Press Start");
  delay(2000);

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(" Set Expose Time");
  lcd.setCursor(0, 1);
  lcd.print("Min: ");
  lcd.setCursor(9, 1);
  lcd.print("Sec: ");

  while (startCountdown == false){
    logic2 = digitalRead(secondsButton);
    //SECONDS ADJUST
    if (logic2 == LOW){
      seconds ++;
      delay(300);
      if (seconds >= 60){
        seconds = 0;
        minutes ++;
      }
    }
    char buffer[3];
    sprintf(buffer, "%2d", seconds);
    lcd.setCursor(14, 1);
    lcd.print(buffer);

    logic3 = digitalRead(minutesButton);
    //MINUTES ADJUST
    if (logic3 == LOW){
      minutes ++;
      delay(500);
    }

    lcd.setCursor(6, 1);
    lcd.print(minutes);

    logic4 = digitalRead(resetButton);
    //RESET ADJUSTMENTS = SETS SECONDS AND MINUTES TO 0
    if (logic4 == LOW){
      seconds = 0;
      minutes = 0;
    }

    logic1 = digitalRead(startButton);
    //START
    if (logic1 == LOW){
      startCountdown = true;
    }
  }

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Exposure Start");
  lcd.setCursor(0, 1);
  lcd.print("Timer = ");
  lcd.setCursor(8, 1);
  lcd.print(countdown);
  lcd.setCursor(12, 1);
  lcd.print("Secs");

  buzzer();
  uberTime();
}

void loop(){
  splashscreen();
  logic1 = digitalRead(startButton);
  logic2 = digitalRead(secondsButton);
  logic3 = digitalRead(minutesButton);

  if (logic1 == LOW){                 // SETUP & START BUTTON
    setupTimer();
  }

  Serial.print("startButton = ");
  Serial.print(digitalRead(startButton));
  Serial.print("resetButton = ");
  Serial.print(digitalRead(resetButton));
  Serial.print("minutesButton = ");
  Serial.println(digitalRead(minutesButton));
  delay(100);
}

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