Exposure Trigger

[juliangudmundsson2]

Reading this document

https://www.krontech.ca/wp-content/uploads/2019/12/External-trigger-tutorial-final.docx.pdf

it states “Exposure Trigger: When you turn this on, the camera will not capture any frames until it detects a change on the trigger signal from inactive-to-active, at which point the camera will expose exactly one frame and then go back to waiting for another inactive-to-active change on the trigger signal.”

When I try this it records frames from the signal goes high at the framerate until the trigger signal goes low again

I want it to just record one frame on each transition from low to high

What is wrong here?

https://photos.app.goo.gl/33e2vvg5vyHWeDtQ8

any input is much appreciated

[clkdiv]

I just can confirm that this is the same here: if the high signal duration is longer than the exposure time, it works like a gate, meaning frames are taken as long as the signal goes low. Thus the documentation is wrong here or it is a bug.

Isn't it possible for you to let the signal drop again after e.g. 100 microseconds?

[juliangudmundsson2]

I ran this little program on an arduino that takes the trigger signal from a photodetector and emits a 1ms pulse for every transition

The camera then exposed two frames for each trig

Afterwards i reduced the framerate to half with avidemux discarding the first frame of each exposure that aways was noisy (parasitic exposure, something)

problem solved for now

yours

Julian

/*
  State change detection (edge detection)

  Often, you don't need to know the state of a digital input all the time, but
  you just need to know when the input changes from one state to another.
  For example, you want to know when a button goes from OFF to ON. This is called
  state change detection, or edge detection.

  This example shows how to detect when a button or button changes from off to on
  and on to off.

  The circuit:
  - pushbutton attached to pin 2 from +5V
  - 10 kilohm resistor attached to pin 2 from ground
  - LED attached from pin 13 to ground through 220 ohm resistor (or use the
    built-in LED on most Arduino boards)

  created  27 Sep 2005
  modified 30 Aug 2011
  by Tom Igoe

  This example code is in the public domain.

  https://www.arduino.cc/en/Tutorial/BuiltInExamples/StateChangeDetection
*/

// this constant won't change:
const int  buttonPin = 2;    // the pin that the pushbutton is attached to
const int ledPin = 13;       // the pin that the LED is attached to

// Variables will change:
int buttonPushCounter = 0;   // counter for the number of button presses
int buttonState = 0;         // current state of the button
int lastButtonState = 0;     // previous state of the button

void setup() {
  // initialize the button pin as a input:
  pinMode(buttonPin, INPUT);
  // initialize the LED as an output:
  pinMode(ledPin, OUTPUT);
  // initialize serial communication:
  Serial.begin(9600);
}


void loop() {
  // read the pushbutton input pin:
  buttonState = digitalRead(buttonPin);

  // compare the buttonState to its previous state
  if (buttonState != lastButtonState) {
    // if the state has changed, increment the counter
    if (buttonState == HIGH) {
      // if the current state is HIGH then the button went from off to on:

      Serial.println("off");

    } else {
      // if the current state is LOW then the button went from on to off:
      Serial.println("on");
      buttonPushCounter++;
        digitalWrite(LED_BUILTIN, HIGH); 
        delay(1);                     
        digitalWrite(LED_BUILTIN, LOW);

      Serial.print("number of trig: ");
      Serial.println(buttonPushCounter);
    }
    // Delay a little bit to avoid bouncing
    delay(50);
  }
  // save the current state as the last state, for next time through the loop
  lastButtonState = buttonState;




}