Jashwanth Bamidi

Power distribution and measurement Ongoing · board fabricated and in the vehicle

Eco Illini

One 36 V battery powers every subsystem on the car. The power distribution board turns it into protected 12 V and 3.3 V supplies.

Role
Power Distribution Unit Lead
When
August 2025 – present · Champaign, Illinois
Tools
KiCad, LTspice, Oscilloscope, STM32, INA228, CAN, SPI, I2C
Three-quarter Blender render of the assembled Eco Illini power distribution board with yellow XT60 connectors, a labeled black relay, microcontroller, regulator circuitry, inductors and a labeled metal DC/DC module on a green PCB.
Render of the design file. Blender render from the e7 PDU rev. 0 geometry, with recreated component labels. L1 and F1 use representative models.

What I did

I designed the schematic, chose the parts and laid out the four-layer board in KiCad. I assembled the fabricated board and validated it on the bench and in the car.

I also lead the PDU and Joule Meter teams. On the Joule Meter I wrote the STM32 measurement firmware; its board layout was a team effort.

Result

  • Both rails held under 50 mV peak-to-peak ripple, in LTspice and on the bench.
  • Joule Meter energy readings within 1% of a calibrated supply, using an INA228 on a 10 mΩ shunt.
  • 30% fewer prototype iteration cycles year over year across both teams.
  • These are summary figures; scope captures and calibration logs aren't shown yet.

Design decision

Protection on the board itself

Fusing, reverse-polarity protection and the E-STOP path live on the PDU. A reversed connector or a downstream short during student assembly stays a contained failure instead of reaching the whole car.

PDU, personally designed and laid outJoule Meter, team board; my firmwareI2CBattery bus36 VProtectionfuses, reverse polarityE-STOP pathBuck conversionstep-down12 V railLDO3.3 V railSubsystemsTemperature sensingShunt10 mΩINA228current / energySTM32 firmwareregister-levelVehicle telemetryCAN · SPI · I2C
  5. 12 V rail
  7. 3.3 V rail
  8. Subsystems
  10. Shunt10 mΩ
Protection. Fusing limits a downstream fault; reverse-polarity protection survives a backwards connection during assembly and testing.
Illustrative. Power path and measurement path. Functional drawing, not a pinout. Highlight a path or select a block.

More detail

Constraints

Several teams build boards on different schedules, and the PDU is where they all meet. It is fabricated outside and hand-assembled by students, so parts and layout had to suit rework.

Power and protection

Power enters through fusing, reverse-polarity protection and the E-STOP path. Buck converters and LDO regulators produce the 12 V and 3.3 V rails, and the board carries temperature sensing.

Measurement is a separate branch: the INA228 reads the shunt, the STM32 turns its registers into energy, and the result goes out over CAN, SPI and I2C.

Bring-up and testing

Validation covered load regulation, transient response, thermal behaviour and in-vehicle integration. Ripple was checked in LTspice first, then with an oscilloscope.

Regulator part numbers, board dimensions and rail currents are left off this page.

Other design decisions

  • Buck conversion first, LDO where it helps

    Switching regulators for the big step down from 36 V. Instead of: linear regulation throughout.

    A linear drop from 36 V turns most of the power into heat; bucks fix that but add ripple and layout sensitivity.

  • Four layers

    A four-layer stack. Instead of: a cheaper two-layer board.

    Costs more, but solid reference planes keep return paths and regulator loops tight.

  • Archer AviationTest-stand flow-controller board and firmware, plus HV stand wiring, instrument automation and reliability planning.
  • High Speed FPGA PCBA planned FPGA and DDR memory board for learning power delivery and signal integrity before fabrication.