I built Hawi three years ago, and many of the component choices I made back then have better alternatives now. This article shows the upgrades I did, and also adds a more detailed description of the electronics I used.

For a look at what Hawi originally was see this previous article.

For comments please use my Google+ page

• A Raspberry Pi Model B replaces the Asus Eee PC Netbook.
  The Rapberry Pi can do Wifi, and can serve as the gateway to bigger desktop computers. It's smaller, cheaper, and can also do I2C. This means the Arduino's USB is now free for other use.
• To provide power to the Raspberry Pi, I added a 5V/3A DC converter from Adafruit
• A PCA9685 servo controller from Adafruit replaces the Phidgets controller I used before.
  It's much cheaper, and easier to use since it uses the I2C protocol instead of requiring a special USB library.
• To provide power to the servo controller, I added a PTN78020W 6V/6A Switching Regulator by Texas Instruments
• An Arduino Mega replaces the three Arduino Duemilanoves I had before.
  It has enough IO pins to handle all four motors, and more.
• Wheels have changed as well. I found some cheap motor + gearbox + wheel assembly on ebay. Definitely lower quality than what I had before, but at least their stall current is below 2A, which is perfect for the L298 H-Bridges.

Here are some pictures of the new Hawi: a top view, a bottom view, a closeup on the new wheels, as well as the little resistors plugged into the Arduino's analog ports for back-EMF feedback from the motors.

Here is where things get more technical. I had to separate the full diagram into three separate parts for clarity. In reality, if you wanted to build your own Hawi, you would need to wire as shown in all three diagrams combined.

A high level overview showing the interconnection between the main components: the Raspberry Pi, the Arduino Mega, and the servo controller.

You can click on the image below for a higher resolution version, or on the Google Drive link for even more detail.

The motor drive, which is the most complex from the electronics stand point. It shows the connections between the DC motors, the Arduino Mega, and the L298 H-Bridges. It also includes the back-EMF feedback loop going back into the Arduino's analog pins, through a set of resistors. For more background, you can refer to my previous article on how I use back-EMF.

You can click on the image below for a higher resolution version, or on the Google Drive link for even more detail.

And finally the servo drive. The simplest of the diagrams. It just shows the power supply to the servo controller, and the connections to the servos.

You can click on the image below for a higher resolution version, or on the Google Drive link for even more detail.

Here's a video of the new version in action. Actually this videos shows the older Hawi, which has been upgraded just as the new one has, except it still has its original high quality wheels.

Yes I have built two Hawis now :) It also has this chain driven frame attached to it, which allows it to hold a marker and possibly draw in the future. Perhaps some day, it could be used to push buttons as well.