Decoding the Droid

Do you have a few Nomadic Technologies N150 robots sitting around that you are not sure what to do with? Chances are that you do not, because these robots have not been manufactured for almost 25 years, and they were niche machines at that time. They were originally targeted at researchers studying robot exploration problems, like how to get a robot to solve a maze. These days you can do that easily enough with an Arduino or Raspberry Pi and an inexpensive robotics platform, but in the 1990s, it required some cutting edge hardware.

Even though you probably do not have the good fortune to have an N150 in your spare parts bin, you will likely still find YouTuber Clay Builds’ recent video quite interesting. Clay Builds managed to get his hands on one of these robots at an auction. Since it came with no documentation and the company that produced it has been out of business for a quarter of a century, the only way to make any use of it was to first reverse engineer it. This can be a very difficult task under even the best conditions, but with the robot in a nonfunctional state, it was all the more challenging.

On initial inspection, the N150 has a rotating turret at the top that is lined with ultrasonic sonar modules, which makes sense for a robot designed for exploration. A set of three wheels are on the bottom of the robot, which can be turned for steering and are driven by a large brushed DC motor. Inside the anodized aluminum body of the robot was a slew of PCBs — each ultrasonic module and wheel had its own PCB, and several larger PCBs were located in the center of the casing.

Clay Builds tears the robot down and goes deep into the operation, providing information that is useful well beyond this particular situation. This knowledge could be useful to anyone that is trying to reverse engineer unknown hardware. In the course of this teardown, Clay Builds found the motor control boards and, as a first step in interacting with the hardware, connected an Arduino Pro Mini development board to it. After some experimentation with sending different signals to the inputs of the motor controller, he was able to drive a spare DC motor that he had on hand.

With that out of the way, a set of very beefy batteries were installed in the case to supply the robot with the 24 volts that it requires for operation. Next, Clay Builds wanted to be able to interactively drive the robot, so he wired a PlayStation controller to a Teensy 4.0 (as it supports the 3.3 volt logic level required by the controller) for input. With a bit more reverse engineering work, Clay Builds also figured out how to drive the motor that controls the steering, then wrote a simple program to translate the requested actions into signals to send to the motor controllers.

After reassembling the N150, Clay Builds was able to successfully drive the robot around his house using the PlayStation controller. That was a big achievement, but there is still a lot of work to do to understand this robot, so be sure to stay tuned for future videos.