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1  Using Arduino / Project Guidance / Re: does not fire if quick on: February 25, 2012, 02:28:32 pm
I used the phototransistor and it works!!! Thanks a lot! I'll try it on something faster than a piece of wire in my fingers.
2  Using Arduino / Project Guidance / Re: does not fire if quick on: February 25, 2012, 01:41:33 pm
It has Cds Photoresistor as a light sensitive element. I recently got IR barrier kit - I probably could use it! Though I am still uncertain what kind of IR sensor it uses.
3  Using Arduino / Project Guidance / Re: does not fire if quick on: February 25, 2012, 11:31:17 am
Thanks. I'll try.
4  Using Arduino / Project Guidance / does not fire if quick on: February 25, 2012, 11:13:17 am
Hi. I am a newbie in Arduino. I am fighting with this issue for quite some time. I am trying to implement a classic Arduino project: flash triggered by a sensor. I have a laser that shines on a DFRobot light sensor, when laser light is blocked (value becomes more than the threshold), Arduino sends signal that goes through an optoisolator and triggers a Canon flash. (similar to mrichardson23's project from Make magazine) . For now there is no camera. Everything works - I photographed a Coke can falling into an aquarium (without fish) - looks good! But I wanted to photograph a much faster event - a whip overcoming sound barrier. My setup does not work for fast traveling objects, even a finger quickly moved through the beam does not fire the flash. Below is my code. Please help.
P.S. My threshold is just over the light level when the laser shines.

int LASER_PIN = 5;
int FLASH_PIN = 4;
int SENSOR_PIN = 0;

void setup() {
    pinMode(FLASH_PIN, OUTPUT);
        digitalWrite(FLASH_PIN, LOW);
        pinMode(LASER_PIN, OUTPUT);
        digitalWrite(LASER_PIN, HIGH);
void loop() {
              int sensorVal;
              sensorVal = analogRead(SENSOR_PIN);
      if (sensorVal > SENSOR_THRESHOLD) //If we sense a shadow:
      digitalWrite(FLASH_PIN, HIGH); // fire flash
      digitalWrite(FLASH_PIN, LOW);
5  Using Arduino / Sensors / Re: jumping light sensor readings on: September 16, 2011, 12:55:38 pm
Thanks for the reply! Though, It doesn't fully explain... MM shows big difference dark/light: 20mV/400mV. MM is inertial and that can mask actual jumping, but it should not have hidden the high background noise that should raise background signal close to 250-300mV to get 45 vs 65 values. In other words, the difference between dark/light is still significant - ~380mV and this difference should have been reflected on the Serial Monitor.
P.S. And I don't have another sensor to try...   smiley-sad-blue
6  Using Arduino / Sensors / jumping light sensor readings on: September 16, 2011, 10:22:07 am
Hi, all. I am just starting with Arduino (and electronics)... I am trying to use a light sensor to trigger a flash if laser beam is blocked. Unfortunately, I don't know the model of the light sensor, but it seems to me it is not LDR type, but more like a photovoltaic panel (4x4 mm) - it creates potential difference in proportion to light falled onto the sensor. I checked the sensor with MM - it does respond to light and in the dark it is 0 mV and with the beam is ON - about 390 mV. As I understand the sensor should be plugged into Arduino differently than LDR, and the + side directly into A0 and - (via resistor or not) into Ground. Prior to calibration and without mapping to 0-255, when I watch via Serial Monitor for the sensor values - they vary significantly (without the beam - 38-47, with beam - 68-95).  I also expected the difference with/without beam to be larger assuming I have 1024 points of resolution per 5 Volts.  What do I have wrong? Do I have my light sensor connected properly?
Thanks in advance.
P.S. I don't want to smoothen the readings as I'd like to trigger the flash ASAP after the beam is broken.
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