Retroreflector Sensor Application

I have what I believe to be a somewhat unusual application and am looking for guidance after spending quite a bit of time on the web researching. I have an observatory and the top dome rotates as needed to align the observing slit with the scope. What I’d like to do is install an optical sensor on the fixed portion of the dome ring, and then detect strips of reflective tape that I will place at 360 position on the outer ring (one for each degree), as they go by. during dome rotation.

I’m looking for a very compact digital sensor with sensitivity adjustment that will be able to distinguish the reflective tape from the non reflective ring (dark blue). The sensor would be 0.5 to 1" from the reflective tape.



It sounds like there is a large contrast in the reflectance of the surfaces you are trying to detect, so one of our QTR Reflectance Sensors might work well. These sensors direct an IR light at a surface and have an output related to the amount of light returned back to the sensor. Please note that the output from these sensors can be affected by other sources of IR light like sunlight or some fluorescent lights. Shielding the surface the sensor is measuring from sources of interference can help the sensor return more repeatable measurements.

We generally recommend a maximum detection distance of 0.375" for the sensors, however I suspect the retroreflective tape you are using would return more light to the sensor and provide a little better range.

Our QTR sensors are available with two different output types (“RC” and “A”). The “A” versions return an analog voltage that is proportional to the light reflected where the “RC” version requires a more complicated algorithm to measure the timing of a digital signal. You can find out more about the signaling characteristics of these sensors on their product pages.

We do have a number of other IR sensors that might work, however the QTR sensors are inexpensive and sound like they are most suited for your application.



Appreciate the timely response. I’m going to give the QTR-1RC a shot. I’ll report back with my findings.