Scan slides with DSLR and slide projector using arduino and some relays.

DSLR_slide_scanner.ino

/*
Code uses an Arduino Uno to control a slide scanner and a DSLR to make it easier to digitize slides.

I got these relays on Amazon for about $3 each.  They take 5VDC, Gnd, and a low 
voltage to close the normally open relay.  http://www.amazon.com/gp/product/B00G9TQH8U

Features: 
This relay module is 5V active low. 
It is a 1-channel relay interface board, which can be controlled directly by a wide range of microcontrollers such as Arduino, AVR, PIC, ARM, PLC, etc.  
It is also able to control various appliances and other equipments with large current. 
Relay output maximum contact is AC250V 10A and DC30V 10A. 
Standard interface can be directly connected with microcontrollers.   
The working status indicator light is conducive to the safe use. 
Widely used for all MCU control, industrial sector, PLC control, smart home control. 
With opto-isolator, more stable and reliable. 

Specifications: 
Working voltage: 5V 
Channel: 1 channel 
Item size: 5.6 * 1.7 * 1.7cm / 2.2 * 0.67 * 0.67in 
Package weight: 18g / 0.63oz 

Package includes: 
1 * 1 Channel Relay Module
--

ChrisJ, 2016.01.17
*/

int slideCount = 0;    // the current count of slides imaged
int trayCount = 140;   // the size of the slide tray
volatile boolean runningState = false; //Set the default running state, FALSE = no action, TRUE = scan running
const int runLedPin = 13;    // Set pin for LED that marks if scan is running
volatile const int button = 3;
volatile const int bounceDelay   = 5;     //Time in usec to wait for debounce action

const int relayProj = 7;  // the pin used for the projector relay
const int ledProj = 11;   // the pin used to indicate we're running the projector code
const int trigSlide =  250;    // time in msec defining how long relay should be activated to go to next slide
const int slideDrop = 1500;   // time in msec to wait for slide to move into place

const int betweenSlides = 12000;   // time delay between shutter release and next slide action

const int relayCam = 8;  // 
const int ledCam = 12;
const int trigShutter =  250;    // time in msec defining how long relay should be activated to go to next slide
const int shutterTime = 1500;   // time in msec to wait for slide to move into place

// Status LED vars
long cycleCount   = 0;            // Keep track of cycles in loop
int cycleDivider  = 10000;        // After how many cycles the status LED will change
boolean ledStatus = false;        // LED will be off to start with

void setup() {
  Serial.begin(9600); 
  pinMode(button, INPUT);     
  pinMode(runLedPin, OUTPUT);       //Set pin for indicator LED
  pinMode(ledProj, OUTPUT);     
  pinMode(ledCam, OUTPUT);     
  pinMode(relayProj, OUTPUT);     
  pinMode(relayCam, OUTPUT);     
  attachInterrupt(1, startPause, RISING); //Enable interrupt for start/pause button

  digitalWrite(relayProj, HIGH);   
  digitalWrite(relayCam, HIGH);
}


void loop() {
  if (runningState) {  
    digitalWrite(runLedPin, runningState);  // Status LED permanently lit duirng scan
    advanceSlide();
    delay(500);
    takeImage();
    slideCount += 1;
    
    Serial.print("Captured slide: ");
    Serial.print(slideCount);
    Serial.print(" waiting for ");
    Serial.print(betweenSlides);
    Serial.println("ms...");
    
    if (slideCount > trayCount) {
      runningState = false;
    }
    
    if (runningState) delay(betweenSlides); // if still running, wait for x msec before proceeding to next slide  
  } else {               
    blinkLED(runLedPin);                    // blink the status LED to indicate we are ready
  }
}

void advanceSlide() {
  digitalWrite(ledProj, HIGH);   // turn the LED on (HIGH is the voltage level)
  Serial.println("triggering slide");
  digitalWrite(relayProj, LOW);
  delay(trigSlide);
  digitalWrite(relayProj, HIGH);   
  delay(slideDrop);
  digitalWrite(ledProj, LOW);   // turn the LED off (HIGH is the voltage level)
}

void takeImage() {
  digitalWrite(ledCam, HIGH);   // turn the LED on (HIGH is the voltage level)
  Serial.println("triggering shutter");
  digitalWrite(relayCam, LOW);
  delay(trigShutter);
  digitalWrite(relayCam, HIGH);
  delay(shutterTime);
  digitalWrite(ledCam, LOW);   // turn the LED off (HIGH is the voltage level)
}

// Start/pause button press interrupt ISR - changes the running state
void startPause(){
  int j;
  for (j=0; j<bounceDelay; j++) delayMicroseconds(1000);          //button was pressed, now wait for a little bit to check state again (aka soft debounce)
  if (digitalRead(button)==HIGH) runningState = !runningState; // if still pressed, then change runningstatus
}

// Blink ready
void blinkLED(int ledPin) {
    cycleCount++;                          // increment cycle count on each loop
    if (cycleCount % cycleDivider == 0) {  // change LED status every so many cycles
      ledStatus = !ledStatus;              // change LED status
      digitalWrite(runLedPin, ledStatus);  // Turn LED on or off every X cycles
    } 
}