Glen, our newest team member from Australia, has shared his new Wheelchairbot with us. He’s using two Parallax continuous rotation servos and some Tamiya plates to quickly hack together the body. What’s really impressive is the inclusion of an ultrasonic range finder to sense distance to nearby objects and then speaking it back.
Here is a quick video of Glen showing his bot using text-to-speech to speak the distance between it and a nearby object.
In order to make this work, Glen has to solve a challenging problem in getting two-way serial communications to work using Python on Android. It might sound easy but PySerial is not included in the Android Scripting Environment, so he had to roll his own code to reliably read and write to the serial port. After a lot of trial and error, the code is now in the open source Cellbots project so you can try this yourself.
The Arduino code has also been upgraded to handle a forward-facing and/or downward facing ultrasonic range finder. We’ve tested with Parallax and MaxBotix parts, both of which share the same code. If you don’t have one, just set the range margin setting at the top of the Arduino code to zero and it won’t bother trying to check the distance.
Glen is also using a $2 Sparkfun 3.3v to 5v level converter, which will save you a lot of hassle in wiring up your 3.3v phone to a 5v Arduino board. Much easier than using a hex inverter chip for the 3.3v to 5v side, and two resistors for the 5v to 3.3v side. We’ve tested the code using both methods and they each work fine but the chip makes wiring simple and is easier to find.
We really appreciate the code submissions Glen made and he’s now an official team member. You can read more about Glen on his Garrows.com website, and we have some additional photos of Wheelchairbot in the Cellbots Picasa gallery below.
