Sharp IR Distance Sensor with mirror?

I want to rotate 360 degrees with a CR servo, and take distance measurements. The best way I can think to do that is to use a mirror attached to the servo (at a 45 degree angle) and perch the sensor pointed down, directly above the mirror. The mirror would spin, and the IR sensor would “see” all around (obviously except for the post holding up the IR sensor, but that’s fine).

Will this mess up the IR sensor, because it measures angles of incoming light, or will this work?


If you look through the datasheets for the Sharp IR distance sensors, you will see that the schematic diagrams indicate that the light returns to either a PD or a PSD on the sensor. I found a webpage that contains some information on how the PSD works, and although I do not know how accurate it is, it could be useful. This means that the angle of the light returning to the sensor is important, though I do not know that this would necessarily rule out using a mirror.

You certainly could experiment with one of these sensors and a mirror to see how it behaves, but we have not done a detailed characterization. As a quick experiment, I took one of the analog sensors I have in my office, held a piece of semi-polished stainless steel (one of our Zumo blades which I had previously polished) at an angle above it and got an output voltage that seemed to go up as I held the contraption closer to the wall and went down as I moved it further away. A glass mirror (which has two reflective surfaces) or an acrylic mirror (which also has two reflective surfaces and might not work well with IR) might behave differently.

A more straight forward alternative might be to simply mount the sensor on a servo and aim the sensor directly at the objects you are trying to determine distances to. If you wanted something with a continuous rotation, you might be able to use a slip ring for the wires.


Can you mount a slip ring like that on a servo so it is in the central axis? It didn’t seem obviously mountable on a servo?

Google is my friend :slight_smile: - gearing to a shaft above the slip ring seems the solution for these. Do you have experience with these? I have a sharp IR, will the signal noise mess with my readings? (If not, it’s worth the small cost to test!) Thanks again!


We have not tried those slip rings, so we can’t say how much noise they might introduce into your system. If you test them, we would definitely be interested in hearing how it works out.