'LVC2' - Lithium Low Voltage Cutoff for Twin
This device monitors two separate packs in a twin which has two controllers. This forces both motors to cut together when the battery is flat thus eliminating assymetrical thrust problems. Since voltage is load-dependant, by logging the voltages from both packs in flight, one can pick up whether both motors are performing equally.
PLEASE NOTE: THIS DESIGN IS PROVIDED WITHOUT WARRANTY AND FOR PERSONAL NON-COMMERCIAL USE ONLY.
The program is written for Microchip's PIC12F683 chip and the BoostC compiler. Other chips with at least 2 ADCs should work too.
The exact workings of this device are recorded in the above C file. However, the following describes it operation and some design features.
* The program is based on LVC1 so you should read that page for more details.
* One significant difference is that the program checks that both packs are connected and exceed the minimum voltage before starting up fully. With an appropriate threshold this could prevent you taking off with flat batteies. It also means there is less risk of flight data being over-written in error between flights.
* The circuit board has two connectors for the two packs. The third cell in Pack1 is used to feed the 5v regulator. Ground is common to both packs, as well as both ESC outputs and the RX input. The positive lead from the RX is passed through to both ESC's so they are powered by the receiver.
* I have chosen to log the minimum voltages on both packs (instead of throttle position). I think this will provide meaningful data on how both motors are performing because if they are different this is likely to reveal itself as a different battery voltage under load.
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