BPS Leader PCB

GitHub:

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

Old vs New Design:

Requirements:

• Interface with three Contactors
• Add connectors for the LeaderSOM
• Control a fault light
• Control multiwire fans
• CAN interface with the Orion to control the fans

Schematic:

• 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 
    • 
• 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
  • 

PCB:

• The board is the same width as the LeaderSOM since connectors on all 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

Improvements:

• 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
• The board layout was made in imperial (not standard) and multiple things are unaligned