KhatkaPi Baseboard

KhatkaPi Baseboard.

 

I have designed and already tested baseboard to support Raspberry pi 5 running  Openplotter open source project software and provide exceptional protection for the electronics in marine environment.

General design strategy points

  • Designed for Rpi5
  •  Intentionally designed as Baseboard form factor rather HAT.
    • You may use any heatsinking cases and NVRAM SSD adapters.
    • Rpi and peripherals naturally installed in IP67 box to protect from elements.
    • Provides some additional separation between external interfaces and Rpi.
  • Fits in standard IP 65-67 Electrical Project box 11.42" x 8.27" x 3.94"(290 x 210 x 100 mm).
  • All interfaces protected from ESD up to 15KV air discharge and 8KV contact discharge
  • Board designed to minimize loss in case of lightning strike, user mistake or other equipment malfunction.
  • In most cases uses COMMON GROUND rather galvanic isolation approach to protect against lightning strike.
  • However, most interfaces have isolated data lines to protect Raspberry Pi from damage.
  • External interfaces have separated power regulators for redundancy and extra protection.
  • Sure board is double coated with high grade conformal coating to protect electronics from moisture and salty air. 

Features:

  • Input power over voltage protection up to 40V.
  • Input power under voltage protection <9V to save battery from deep discharge.
  • Connector for the switch to override add under voltage protection (down to 6V)  in case of emergency. 
  • Independent 5V power regulator for Raspberry. 6A maximum power capacity to support future Rpi and cover any inrush power surges.
  • Connectors to connect external switches and on board buttons for System power control. 
    • Power On (hard power ON).
    • Power Off (hard power OFF).
    • Shutdown button.
  • Auto power off all but AIS when Rpi completed shutdown.
  • Switched 12V output (up to 4A) providing power to auxiliary devices when Raspberry is power on. 
  • Place to install HDMI splitter next to raspberry.
    • Capability to use two mirrored displays from one  Rpi w/o software tricks
    • Additional protection for Rpi HDMI interface.
    • Splitter can be powered USB A connector. 
    • As an option splitter can be powered from HDMI interface, but it will require sope changes inside the splitter.

  •  On the board interfaces:

    • On board ICM-20948 based IMU 
      • sensor located on the far corner of the board to have minimal interference with on board magnetic fields.
    • PWM controlled FAN 
      • installed on the board to run air inside the box to provide better heat distribution and let raspberry transfer heat to external box surface.
    • Socket for Arduino Nano to be used as weather sensors controller based on open source project Pypilot - weathersensors.
      • On board barometric pressure sensor BMP280 connected to weathersensors board.
      • Isolated  serial connection to Raspberry
      • Powered form switched 12 volt 
      • external connector lines ESD and overvoltage protected.
    • 3 Connectors for 1-Wire onterface sensors
      • Interface for External temperature sensors.
      • Connectors lines ESD and overvoltage protected.

  • External interfaces:

    • I2C interface connector
      • if you wish to use external IMU or other I2C devices. 
      • Interface ESD protected, but not isolates.
      • Only distance or in the box connections recommended.
    • Two NMEA 0183 
      • Two full isolated and protected NMEA 0183 interfaces.
      • Intended to use one for Depth sounder
    •  Interface to connect Maiana AIS/GPS 
      • Maiana direct connection with RJ45 connector 
      • Power and transmit control external switches connectors.
      • Independent 3.3V regulator for interface.
      • On the board indicators.
      • isolated serial interface.
    • Interface for the PyPilot Motor controller.
      • Serial data lines are isolated and protected.
      • 5V power is provided from separated from Rpi regulator.
    • Auxiliary micro-controller serial interface.
      • Microcontroller provides access to Rpi GPIO signals over serial interface.
      • For example remote hard buttons module will be designed.
      • Auxiliary micro-controller serial interface isolated and protected.
    • Two four-port USB hub (total 8 ports)
      • All 8 ports have 12kV direct discharge ESD protection and common mode filters. 
      • Each hub has independent power regulator with 2A load capacity for each group.
    • Two 5V power output
      • two additional USB ports with power only outputs. Up to 1.5A may be used total.

Real life prototype photo.


 

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