FUTURE: 2nd Generation Power/Umb controller
We hate primary batteries. But we hate unreliable rechargeables even more. And we don't want to go through the pain of building our own exquisitely sensitive charge control circuitry for battery charging and status, and we sure as heck don't want to go through the process of trying to get samples of Li-Ion batteries (what a pain in the butt).
The obvious thing to do is to use other people's work: the Smart Battery System! See the BatteryPack discussion for more Smart Battery links.
This future node has three main functions:
- It interfaces two smart battery packs and the rest of the avionics system (i.e., CAN bus),
- It charges the smart battery pack (since the SB only has a charge monitor onboard),
- It monitors the umbilical cord connector and asserts the "RocketReady" signal (which throws an interlock relay on the main motor igniter firing board).
Here's what we imagine it to be:
- A standard CAN Node (a PIC18F458 hooked to the CAN and power buses).
- One or two Li-ion Smart Battery (i.e., onboard battery monitoring hardware)
- A level 2 or 3 Smart Battery charger (talks SMBus (I^2C) with the battery - e.g., the Linear LTC1759 SMB charger IC).
- Processor listens in on charger/battery conversation, gives commands as necessary and relays information to CAN bus.
- Processor asserts RocketReady when told to do so by the FC.
- Processor senses umbilical disconnection (i.e., a launch detect mechanism).
Sketches:
Here's the block diagram:
