Poor man's laser sensor


If I take a small red laser like those lasers used in powerpoint presentations and couple it with an IR detector enclosed in a little black tube, so both are colinear. Will the detector detect the dot splash? (Or do I need a different kind of detector?

Thanks amigos, -Migs

Interesting idea. My first guess would be no, since ordinary laser pointers put out light in a very narrow wavelength range (ideally all at one wavelength) in the visible spectrum, not the infra-red, but most IR emitter/detector pairs work in the very near infra-red, so one might just pick up a red laser dot, especially one aimed right at it. I’ll give this a quick test when I get to work tomorrow.

Assuming this did work, what are you planning to do with it (i.e. make a laser security grid)?


Hi Adam!

What I want to do is put the sensor duo on a servo and rotate it to detect the edges of a sumo bot, so I can then plot a path around him more accurately. The implications are great if we find a sensor that detects that wavelength. By moving the duo up and down and left and right we can make a “poor man’s laser scanner”. I’m glad you will try it. I’m off on a trip until Wednesday, so I wont surface until then.

All the best, -Migs

I didn’t have a lone IR photo-transistor lying around, so I wired up one of those U-shaped IR photo-interrupters instead. I disconnected the transmitting LED, and sure enough, shining a red laser dot (from a nice bright laser module I gutted out of a laser-level) right on the receiver completely set it off. When I shined the laser on the other half (shiny black plastic and the IR-transmitting LED) nothing happened, but when I put a white note card over that half and shined the laser on it, the receiver completely picked up the reflection! Awesome!

This probably has a short working range (which I can’t test without breaking my photo-interrupter in half), which sounds like it would be just perfect for you!


Hi Adam!

Thanks for trying the experiment. I’m going to try and replicate it. If I come up with something decent I’ll be sure to let everyone know! -Migs

this is another is a project from a robot enthusiast …


this is using a Hamamatsu S6986 chip to detect the laser.

good luck…


Nice project! I’m curious about how good the output signal is - do you think you could use it for reading some very simple bar codes across the room? Something that you could make, for example, by drawing with a black marker on your reflective tape and read by scanning across the tape. If so, this could make a great room identification system for household robots.

If you happen to have access to an oscilloscope, it would be great to see what a trace of the output looks like as the pointer is swept across the tape.


I am sure something similar to this can be done. I wasn’t able to do it when I tried it, though. I didn’t have the best setup and there were a million things I could have done wrong that made it not work. The key is to make sure whatever is supposed to be sensing the red dot can actually do it, i don’t think my photo sensor was picking it up, which meant nothing happened.

Good luck on the project!