This is my idea for using the LIDAR-lite sensor to produce readings in (as close to) a 360 degree view without spinning the sensor itself. I decided to start this project to give some life to my sensor which had never had a real purpose until now.
Thanks to my 3D printer I was able to quickly produce a "rig" to hold the sensor over a mirror. The mirror is attached to a 3D printed plate that is designed to hold the mirror at a 45 degree angle. This will allow me to bend the light 90 degrees from the sensor's emitter. The mirror holder is attached to a stepper motor that will allow me to rotate the sensor's light in a 360 degree view.
Before I go on I've presented a few issues.
- Blocking the view. To hold the sensor over the mirror there will be an arm somewhere in the 360 degree view. I've already taken some action here and removed some of the arm material. In fact if I remove too much more the PLA plastic I've used won't be rigid enough to hold the sensor still.
- The mirror has to be quite large. This is something I discovered along the way. When it was just an idea in my head the mirror was really small but to ensure both the emitter and receiver are 100% in view I had to use the size you see.
- Knowing the mirror position. Because I'm only using a stepper motor for this first design I get no positional feedback. I'll have to assume the mirror position by starting the motor and firmware at a known point.
- Reading accuracy. By bending the light alone there is going to be a small offset introduced. Then there is the ever changing distance of the mirror as it rotates. I chose to align the emitter of the sensor to the center of the mirror. This ensures the light will project in a parallel plane. When the light is received it might bounce off the high side of the mirror in one direction and the low side on the other. I may or may not concern myself with such slight offsets introduced in the readings.
So to get back to the setup. I had a NEMA 17 motor collecting dust and a recently purchased Teensy 3.1 (it's pink!) and ordered an a4988 stepper driver from Pololu (black edition to compliment the Teensy). I put everything together today and quickly put some 'duino firmware together. What I'm outputting is the current stepper motor position with the sensor reading. I copied a little bit of the first chunks of data into Excel and it looks like I'm off to a pretty good start.
This project was just for fun but has become pretty interesting. I'd like to make everything available to anyone who is interested so let me know if you need the files now. Once I get things polished up I'll attach the source files here.
The first results:
There is also a "live" viewer in the works.
And an action shot (thanks Tom)