The average person knows Roomba as a helpful little robot that can vacuum approximately ten square feet of a home before its collection bin gets full or it gets trapped under a couch. But makers have long seen the potential of Roomba robots as platforms for their projects. iRobot even released a special vacuum-free version of their robot, called the iRobot Create, for people to hack and modify. But any used Roomba is a good jumping-off point for a mobile robot. For example, Alfredo Sequeida used a Raspberry Pi to turn an iRobot Roomba 770 into a flamethrower-wielding deathbot.
The 700 series was the fifth generation of iRobot Roomba robotic vacuum cleaners, which started with the 701 model released in May of 2011. They are now in the ninth generation, so it is possible to find models like the Roomba 770 for low prices at thrift stores. Sequeida purchased his years ago to clean his home, but it sat largely unused. This project gave the forgotten robot new life. Like all Roomba models, the 770 has a sophisticated array of sensors that let it navigate around furniture and avoid walls. Those are part of what makes the Roomba such a desirable development platform.
The other reason that makers love Roomba robots is that they have accessible serial ports. By interfacing with that serial port, makers can send and receive data. In this case, Sequeida chose a Raspberry Pi Zero W for control. A special USB-to-serial cable, which iRobot designed for the Create robots, connects the Raspberry Pi to the Roomba 770. The Raspberry Pi can send control commands to the Roomba, which override the normal autonomous behavior. Sequeida connected an Xbox One controller to the Raspberry Pi through Bluetooth, so you can pilot the robot using that.
The Raspberry Pi also controls servo motors that take care of the flame throwing. A bottle of butane lighter fuel sits on top of the Roomba in a 3D-printed mount. One servo motor opens the butane bottle's valve, a second servo motor moves an igniter in front of the fuel stream, and a third servo motor operates the igniter. Sequeida could have connected an electronic igniter to reduce that to a single servo motor, but this method provided an extra level of safety.
As you would expect, Sequeida's flame throwing Roomba looks like a blast to play with — literally. He can drive it around remotely and trigger the flamethrower at will. Predictably, he used his creation to set many things aflame. The 3D-printed parts around the butane bottle nozzle did end up melting, but we still consider this project a resounding success.