|Xref:||BatteryPackLv2, AandTBatteriesLv2, Lv2PowerUsage|
The Avionics Power System (APS) provides power and load switching to the avionics system. It has:
- A 14.4V (max 16.8V) 4Ahr (4s4p) Lithium Ion battery pack which includes a charge counter and voltage monitoring.
- A Li Ion battery charger based on the Linear Technologies LTC4007, which includes shore power current limiting.
- An interface to the umbilical cord for shore power to charge the batteries or run the avionics system, as well as to assert an ignition interlock with the launch tower called "rocketready".
- An "active diode" controller to switch between the battery and shore power.
- Four power switches to switch various vehicle systems on and off, e.g. RF power amplifiers, flight computer, etc.
- A 5V SPS with a linear bypass for for low power standby
- A PIC18F458 microcontroller to control the system and interface it to the CAN bus.
The current version of the APS is v0.6, which was fabbed by PCBexpress 2004/09/08 and finished 2004/09/19.
Documents with a v0.7 number imply they were updated after the APS was fabbed and thus contain errata and future notes.
A previous version of the APS used a PIC with a single parallel set of International Rectifier IPS5451 intelligent power switches and primary Lithium battery. The board was pretty simple, and then was hacked to death, and the primary Lithium batteries turned out to have only 1/8 of the energy we needed for flight.
- Engineering Notes for APS v0.7
- APS-specific schematic (pdf) created from xfig; includes battery board connections but not SPS
- APS v0.6 schematic (pdf) created from the final EAGLE schematic
- APS v0.6 schematic and board layout (eagle) in a ZIP file
For the battery board schematics and board files, see BatteryPackLv2
Lv2PowerUsage - Power calculations based on LV2 loads
The PIC firmware for the APS can be found at http://cvs.psas.pdx.edu/c/firmware/aps/. In particular, see the aps_exports.h file for information on the APS' CAN messages
We're in process of calibrating the APS node: AvionicsPowerSystemLv2Calibration