SPIRIT rev. 1
Builder: Jan MalasekAfter making some fairly typical beginner robots (line follower, obstacle avoider), I wanted to make something different: a robot that could follow me around. And, what good is a robot that can follow you if it isn't big enough to carry something and fast enough to keep up with you? So, I made SPIRIT (Self-Propelled Infrared Robotic Individual Tracker), a 60-pound robot that could move at 5 miles per hour (over 2 meters per second!).
I built SPIRIT in two years, with two distinct revisions. On this project page, I'm showing some pictures of parts from the first revision that didn't make it into the second revision. The second version was much more polished, but the proof-of-concept components are interesting since they show that you don't need sophisticated equipment to make a unique robot.
Since the robot was big and fast, it was important that it could determine both the direction and distance to me. The solution I arrived at was to wear an IR transmitter and to use two sensors that could determine the angle to the transmitter so that the robot could triangulate my position.
To detect the angle to the IR transmitter, I used an angled mirror spinning below a standard (i.e. Radio Shack) 40 kHz IR receiver that was facing down. The mirror was housed in a light-proof enclosure with a slit in it so that as the assembly spun, the IR receiver would detect the transmitter only when the slit faced the transmitter. A magnet on the housing activated a fixed reed switch so that the speed of the spinning could be regulated. The time from the magnet reference signal to the IR signal, divided by the time for the full revolution, would give the direction to the IR transmitter.
Here we see the implementation of the spinning sensor. Two PVC pipe end caps formed the "light-proof enclosure" that was spun by a Tamiya high-speed gearbox. The large round magnet is visible right next to the Ace Hardware price tag on the pipe cap, and the reed switch is on the right standoff. A ball bearing from a rollerblade wheel held the top of the spinning housing to the acrylic plate on which the IR receiver is mounted.
The whole assembly is almost a foot tall, and there were two of them on the robot separated by close to two feet. Each sensor spun at 600 RPM (10 times per second) with a lot of noise and shaking. But they worked!
Across from the magnet, we see a slit, behind which there is a mirror to reflect the IR up to the sensor. The reflection of the ball bearing is visible.
The frame is made from 1/2" copper tubing.
Spinning sensor control board.
I used a combination of wire-wrapping and point-to-point soldering for most of the electronics.
The MOSFET H-bridge driver board. MOSFETs are mounted to heat sink, seen in upper right.
SPIRIT 1 electronics
Stay tuned for more information....
