Page 399 - Hacking Roomba

380 Part III — More Complex Interfacing

FIGURE 16-18: Virtual Wall taken apart, not much there

To just tell if the lens on top is for a transmitter or receiver, the easiest way is to point a digital
camera at it and see if it lights up. The near-infrared used by remote control IR transmitters are
invisible to the human eye but visible to electronic sensors. Figure 16-19 shows a virtual wall
turned on. You can see light from the directional emitter on the front yet nothing from the lens
on the top. The lens on top is likely only used by the Scheduler variant of Roomba to program
when virtual walls are turned on and off.
Having a nicely machined powered enclosure with both an IR receiver and transmitter is a
great hacker toy. You could uninstall and entirely replace the virtual wall circuitry with some-
thing that responds to arbitrary remote control codes and emits Roomba remote control
codes. Or take advantage of the directionality of the emitter and mount the virtual wall unit
on Roomba like a gun and have laser tag battles between Roombas. If you’re concerned
about power, there are chips by Maxim and others can convert the 2–3V from batteries into
regulated 5 VDC.