QTR-RC Reflectance Sensor - zero output all the time


I’ve recently purchased your QTR-MD-02RC sensor. I connected it to the power supply with 3-5V output and then tried to have a look at the output signal from channel 1 or 3 on the oscilloscope. However, I don’t’ see any changes in the output when I block the sensor with the white surface or change the reflectivity to zero. I see zero output all the time. Could you please advise if I’m doing something wrong? I checked and LED works fine.

I want to use this sensor as “homing sensor” with the stepper motor and your Tic controller. Should I consider analogue reflectance sensor instead?

Thank you.


I am sorry you are having trouble with your QTR sensor. To use it, you must first charge the output node by applying a voltage to the OUT pin. Since you are not doing that, it makes sense that nothing is happening at the output. You can learn more about how to use those sensors in this application note, which you can find under the Resources tab of our QTR sensors product pages.

As for your other question, our analog QTR sensors have a better chance of working for what you are trying to do, but there’s no guarantee it would reach the right voltage thresholds for the Tic’s digital inputs. A digital distance sensor like this could probably work if you can make it reliably trigger in a way that works for your system. (You could consider mounting it sideways so it’s almost like a break beam sensor, instead of sensing something coming directly toward or away from it.)


Manyh thanks Jon. Will try first the analoug sensor. Vasili.