QTR analog sensor readings not stable

mihai · April 21, 2016, 1:26pm

Hi there,

I have purchased several QTR 3A sensors, but I’m not getting stable results from them. It seems that the output either increase or decrease in time.

Here is my test program:

void setup() {
  Serial.begin(9600); 
}

void loop() {
  // put your main code here, to run repeatedly:
  int val = analogRead(0);       
  Serial.println(val);            
  delay(500); 
}

Below, at the end, are the results. You can see that the first reading is 336, but then, in time, decrease to 258. My device is not moving, nothing else is moving around it … so why I have such variation in time?

thanks,
mihai

mihai · April 21, 2016, 1:38pm

Here is another reading. Same sensor, same setup. I have only disconnected the USB cable from my Arduino Nano and then I have reconnected again. Now the values are increasing:

Any ideas?

JonathanKosh · April 21, 2016, 9:25pm

Hello.

We do not expect that much variation from that sensor. Can you tell me more about how you are using it? What microcontroller are you using to read the data? How are you supplying power? How is the QTR-3A mounted? What kind of ambient lighting is the sensor operating in? Can you post pictures that clearly show your connections and setup?

-Jon

mihai · April 23, 2016, 9:49am

I use Arduino Nano in my setup.
I will send a picture soon.
Is there possible to have such variation in a matter of several minutes?
or, something is wrong with my setup ?

JonathanKosh · April 25, 2016, 10:05pm

Like I mentioned in my initial reply, we do not expect that much variation over that much time. If you include a picture of your setup and describe it more, I might be able to determine if there is something obviously wrong with your setup.

-Jon

mihai · April 26, 2016, 6:40pm

thanks!

I think that I have found the problem.
I think that the distance to the surface was too small in my case. If I increased the distance a little bit, the results are stable in time.

thanks again,
mihai