over the pandemic, picked up a BrickPi3. We have an older set of Mindstorm NXT lego motors and sensors, not the newer EV3 ones, so the cpu is rather under powered.

initial notes:

• initially planned to use a pi4, but reading the docs on power, decided to hook up an older pi3 I still had.
• 8 rechargable batteries (NiMh) do not “quite” supply sufficient power 😦 . The system would start, and stop. Plugging in a monitor, I saw the initial color swatch, then some of the text, and the “power lightning” icon, and then it would restart… When plugged in an additional 5v adapter from an android phone, it then would boot and run. The NiMh batteries could supply power for the motors, for a short time.
• found a portable android phone power pack, and adding that to the 5 v supply, with the 8 NiMh batteries was sufficient to get the “basic bot” rolling.
• next project was not portable, dug out an old micro ATX power supply: FYI the Floppy/CD drive connectors have +12V, perfect!

project#2 the pen plotter from:
The Unofficial LEGO MINDSTORMS NXT 2.0 Inventor’s Guide
(our local library has an e-book version on o’reilly)

updated to connect to the BrickPi3

The atx power supply is connected to the battery pack with some alligator clips; not too robust, but sufficient for initial runs. Using sharpies and highlighters to draw, and using regular laser paper.

Some initial runs:

calibration tests. Sometimes leaving the pen down for too long, or too much pressure causes the paper to catch and tear:

Will post update with some code samples (python). here is the brickpi3 repo