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https://github.com/lhr-solar/BPS-LeaderDaughterBoard
Dimensions:
50 x 130 mm
Goals:
- This PCB will act as the main control unit for BPS
- It will interface with the LeaderSOM PCB
- Control Fans and Contactors
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- Interface with three Contactors
- Add connectors for the LeaderSOM
- Control a fault light
- Control multiwire fans
- Can CAN interface with the Orion to control the fans
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- Contactors:
- The circuit for each Contactor is the same
- Contactor_EN is a GPIO signal that controls a driver to turn on the Contactor
- Contactor_Sense is a signal that indicates the state of the Contactor
- D2 is a multi-diode package that acts as voltage clipping for the MCU. This will prevent signals above 3.3V from entering the MCU
- The 1N4448W is a flyback diode, which we use if there is a large current spike while closing or opening the Contactors
- Flyback diodes are important when dealing with high inductive loads
- Fan Control:
- The ADT747 chip uses I2C to send PWM signals and receive tachometer feedback
- Orion Interface:
- If the Orion BMS must be used, we can use this board without the LeaderSOM to control fans
- Orion only gives one PWM and accepts one Tachometer input so the jumpers connect the fan tach and PWM signals
- The ADT747 chip uses I2C to send PWM signals and receive tachometer feedback
- Ignition:
- The Ignition switch uses 12V logic levels, so if we tried to put the 12V signals into our 3.3V logic MCU it would destroy the MCU
- The optoisolators take the 12V logic turn it into 3.3V logic and separate the GNDs
- Strobe Light:
- As per regulations, we must have an external light to indicate to the outside that a BPS fault has occurred
- FAULT is a GPIO signal (3.3V) from the MCU that controls a driver for the 12V light
- D1 indicates whether or not the driver is on
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- The board is the same width as the LeaderSOM since connectors on all the sides of the LeaderSOM, and for size standardization, we chose to only extend in one direction
- All 12V nets were turned into pours
- Contactors draw a lot of current at startup
- Special care must be made to ensure that the right of the board is accessible since there is an SD card and Micro-USB cable
- The bottom of the LeaderSOM has a 12V connector and both CarCAN connectors
- The left of the LeaderSOM has the internal CAN connectors
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- Power Systems will add a fourth Contactor for BPS to control so a fourth Contactor circuit will need to be added
- Add fault LEDs to the board at the bottom
- Board The board layout was made in imperial (not standard) and multiple things are unaligned