Release of updated Rev C PCBs

[caveatron-discuss]

Two new revisions of the Caveatron printed circuit board (PCB) have been released, Rev C.3 and Rev C.4. These are minor updates that replace the real-time clock (RTC) battery with a regulator and add a new component option. The RTC in the Teensy 4 uses far more current than anticipated so the coin cell battery in the Rev C.2 PCB will only last about 45 days before needing replacement. Both of these boards replace the coin cell holder with a voltage regulator circuit that draws the RTC power directly from the main battery pack when the Caveatron is turned off so will last indefinitely, so long as the main battery is not fully discharged. This change integrates the small fix protoboard previously released into the main PCB. The other change in Rev C.4 is to replace the MinIMU/AltIMU with the Pololu LSM6DS33 which has the same functionality at a lower cost.

Also the Bill of Materials has been updated and a new 3D printed bracket was added for the LSM6DS33.

Here is how to pick between the board revisions:

Rev C.4 – This is the preferred board version. Use this one for most builds.

Rev C.3 – Use this version if want to use the Pololu MinIMU or AltIMU modules to provide all of the IMU data and not use the RM3100. This is lower cost but will result in lower quality azimuth data. You can also use this version if you want to use the MinIMU or AltIMU modules to provide just the accelerometer and gyroscope data alongside using the RM3100 for the magnetometer.

Rev C.2 Use this version if you want to use a coin cell battery to maintain the RTC, although the battery will have to be replaced every 6 weeks. Can be upgraded to replace coin cell with modification. It is otherwise the same as C.3. Not recommended.