Hello,
I am trying to learn more about sensors and micro-controllers. I was playing with my Arduino, a motor that spins a disc with a hole in it, a photo-transistor and an LED.
I did various things and setups and in one of the setups I tried to measure the time the photo-transistor is "OFF" and the time it is "ON" (the time the hole is between the LED and photo-transistor and light is reaching the sensor).
What I noticed is that as the motor speed increased, the "ON" time got shorter and the LED intensity was influencing the readings. In other words, I set the motor speed in such a way that the "ON" reading was one millisecond (small hole and fast motor). Without changing the motor rpm, if I changed the LED intensity with a potentiometer, the time reading also changed.
Could someone explain what happened? Does the LED intensity influence the rise and fall times of the photo-transistor and thus the "ON-OFF" times?
What should I do to find out the LED intensity that yields the most accurate measuring results for my project and parts?
Everything is wired like this:
http://learn.adafruit.com/system/assets/assets/000/000/460/medium800/cdslitetestdiag.gif?1340727525
The photo-transistor datasheet is here:
http://www.tme.eu/en/Document/209010fdfa39c018786d416aed2be83e/L-93DP3C(Ver.3).pdf
P.S. I have tried with other photo-transistor models and the results were the same.
P.P.S. I am an amateur when it comes to electronics.
Thank you for your time.
I am trying to learn more about sensors and micro-controllers. I was playing with my Arduino, a motor that spins a disc with a hole in it, a photo-transistor and an LED.
I did various things and setups and in one of the setups I tried to measure the time the photo-transistor is "OFF" and the time it is "ON" (the time the hole is between the LED and photo-transistor and light is reaching the sensor).
What I noticed is that as the motor speed increased, the "ON" time got shorter and the LED intensity was influencing the readings. In other words, I set the motor speed in such a way that the "ON" reading was one millisecond (small hole and fast motor). Without changing the motor rpm, if I changed the LED intensity with a potentiometer, the time reading also changed.
Could someone explain what happened? Does the LED intensity influence the rise and fall times of the photo-transistor and thus the "ON-OFF" times?
What should I do to find out the LED intensity that yields the most accurate measuring results for my project and parts?
Everything is wired like this:
http://learn.adafruit.com/system/assets/assets/000/000/460/medium800/cdslitetestdiag.gif?1340727525
The photo-transistor datasheet is here:
http://www.tme.eu/en/Document/209010fdfa39c018786d416aed2be83e/L-93DP3C(Ver.3).pdf
P.S. I have tried with other photo-transistor models and the results were the same.
P.P.S. I am an amateur when it comes to electronics.
Thank you for your time.