Evolution of a Blog

This blog has evolved as I have as a maker. It starts at the beginning of my journey where I began to re-tread my tires in the useful lore of micro electronics and the open-source software that can drive them. While building solutions around micro-electronics are still an occasional topic my more recent focus has been on the 3D Printing side of making.

Tuesday, October 30, 2012

Power Stability = RPi Stability

The troubleshooting area of the Raspberry Pi forum uses the "check your power" a lot in answer to user problems with crashes and other bad behavior.   At first glance one would almost wonder if this is their version of either the reboot it stupid or RTFM.  In fact, the RPi is enormously, hugely, and frustratingly, sensitive to power issues.

Through the process of integrating my RPi with the robot it is meant to control I have learned more than I really expected about power.    Here are some of the problems that I have had that have tied back to "get your power sorted stupid"!
  1. RPi would not boot as input power was too low.   Would cycle through the color splash, get to the point where power was not adequate, and crash
  2. Wireless connection would drop.   Often occurred at a point where current draw from somewhere other than the RPi would draw down voltage and away goes wireless.
  3. RPi would crash when servos were activated to control the sensor pan and tilt stalk.
  4. Webcam would drop offline.   Finally determined that this was also power related and that it was dropping when power levels to the USB hub dropped.
I have not measured the various thresholds when bad stuff happens but after making the following changes, and running on reasonably fresh batteries, the 'bot is stable:
  1. The Rover 5 comes with a six AA cell battery pack that connects to the Explorer PCB where it is regulated down to a 5v and 3.3v supply.   I added a second six cell battery pack and upgraded the rechargeable batteries in these two packs to high end cells (1850mAh).
  2. To further sanitize the power going to the RPi I added a dedicated regulator that draws directly from the battery circuit and is dedicated to the RPi
  3. Somewhere along the line I read the Explorer PCB manual and realized that it provides three power outputs with one dedicated for servos.   Once I connected the servos to their own power source the servo induced crashes stopped.
I still have one more improvement pending and that will be to have two 3.7v 18560 Li-Ion cells (4000mAh) to drive the RPi with the a dedicated regulator from the main batteries powering the USB hub.

Addendum of 1/11/2012: In the days following this post I was also able to determine that problems with my compass were ALSO power related!

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