QRT-L-1A sensor connection diagram

Hello, I purchased the QTR-L-1A sensor for the first time and now attempt to connect and calibrate it.
Please explain the schematics on the Pololu page for the QTR-L-1A sensor (Pololu - QTR-L-1A Reflectance Sensor (2-Pack)).

  • Are the 220 Ohm and 20k Ohm resistors integrated on the QTR-L-1A board?
  • Is the white reflective surface on the sensor side (where ‘S’ i sprinted on the board), or on the emitter side?
  • A photo of a typical application setup would help. Can you post/provide one?
    Thank you!


  • Yes, the resistors shown in the schematic are integrated on the board; you should generally not need to use any additional external components.

  • The sensor board should be pointed perpendicular to the surface you are trying to detect, with the emitter and detector pointed toward it.

  • We do not have a picture of a full setup with the sensor in a typical application, but here is an image from the sensor’s product page that I modified to indicate the sensing direction:


Brandon, thank you for the clarification. The pic with the indicated sensor direction, and your comments, are helpful. Will you post this on the product website?