After building Nano Mice with students and teachers for a year, I've taken some of the advice I've been given and the lessons I've learned and have redesigned the mouse to be less expensive, easier to build, and more educational.
The most important change is the replacement of the Solarbotics Breadboard Voltage Regulator Kit from Jameco. This change was made for the following reasons:
- The printed circuit board for the Solarbotics Kit had about a 10% failure rate (poor quality control).
- The Solarbotics Kit put the voltage regulator between the switch and the power supply, which caused the battery to discharge even when turned off (poor design).
- Plugging the voltage regulator directly into the breadboard allows students to see how the regulator works (nothing is obscured by the use of a printed circuit board).
- The Solarbotics Kit used a 5 volt regulator. A 6 volt regulator allows for the use of the motors at their full potential (they can take a range between 4 and 6 volts).
- No more through-hole soldering, which means no more need for a high quality soldering iron. A standard run-of-the-mill soldering iron is enough to build the mouse.
Another major change was the frame.
- The new frame has been completely redesigned using OpenSCAD. While the learning curve for OpenSCAD is steeper, it's much more powerful. Changes to the model can now be carried out quickly and easily. This allows anyone with access to 3D printers to modify the model to accommodate parts they have on hand (a different set of servos or battery for example).
- The new frame also includes a socket for a ball bearing which replaces the castor wheel. Not only is this step much quicker and easier-you no longer need to know Japanese to read the instructions!
- The sensor slots have been lowered so that more light is reflect back towards the detector, making them more consistent.
- The center of gravity is a little further forward thanks to the placement of the battery (no more popping willies). This also means you no longer need to remove the battery to calibrate the motors.
Nano Mouse 3.0 is also cheaper. See the Bill of Materials for details.
Last but not least, Nano Mouse 3.0 has a much more thorough set of instructions. Along with a video I've included a slide show that walks through each aspect of the circuit.
Some of you may be wondering about version 2. It died in beta (you can thank my students for helping to eliminate that design).