Power Subsystem Build & Test
Power Subsystem Level Build & Test PhaseDuring this phase, the Power Management Boards were assembled, and testing has begun. The MPPT and the batteries were ordered, the solar panel was tested, and software had been started for the Power Management Board.
Power Management BoardThe Power Management Board was assembled and testing has begun. The assembled PCB is shown below.
The GV-5 Lithium Ion 12.5V MPPT solar charge controller was purchased from batteryspace.com.
18 of the Samsung 35E 18650 3500mAh batteries were purchase from IRM. They will be assembled in either a 3S5P or 3S6P configuration.
Test Results Summary
Solar PanelThe solar panel was tested briefly to ensure it was working by putting a lamp directly over it and measuring the open circuit voltage. The voltage was measured to be 17.03V. This value makes sense because the max open circuit voltage is 24V so when the solar panel is under more light we would expect to see this. The test setup is shown below.
More testing will be done with the solar panel once the MPPT arrives.
Power Management Board HardwareInitial testing of the Power Management Board is done and some more detailed tests are remaining. A picture taken of both the 12V output and the 24V output is shown below.
The test plans are shown below. Some are completed, partially completed, and some have not been started. These tests will all be finished within the next phase.
12V Turn On and Turn Off Voltage
12V Regulation and Efficiency
At 3.4A load on the 12V output a thermal image of the board was taken. The 12V Buck Boost Converter was measured to be around 65 degC. This is warm but is not too much of a concern because the part has internal switches so it makes sense that it is getting hot.
12V Load Step Response
12V Ripple Voltage
24V Turn On and Turn Off Voltage
24V Regulation and Efficiency
24V Load Step Response
24V Ripple Voltage
Power Management Board Software
I2C software has been written to communicate with the MAX34409, 4 channel current sensor and the INA226, power monitor. Data is received by the MSP432 from these sensors and is printed out over UART, shown below. The values of the results have not been checked for accuracy yet. The next step will be to load specific output and verify the current drawn matches our measurement/calculation.
COMMS_SHNT measurement: ff
COMMS_SNS measurement: a5a5a5a5
DACQ_SHNT measurement: 24
DACQ_SNS measurement: a5a5a5a5
EXTRA_SHNT measurement: 0
EXTRA_SNS measurement: a5a5a5a5
CBOB0_SHNT measurement: 0
CBOB0_SNS measurement: a5a5a5a5
SOLAR_SHNT measurement: 2
SOLAR BUS VOLTAGE measurement: 0
SOLAR CURRENT measurement: 2
SOLAR POWER measurement: 0
SOLAR overflow in calculation if bit 2 high: 0
BATETRY SHNT measurement: 1
BATTERY BUS VOLTAGE measurement: ab
BATTERY CURRENT measurement: ff
BATTERY POWER measurement: 1
BATTERY overflow in calculation if bit 2 high: 0
Risk and Problem TrackingAs issues are found with Power Management Board, they are recorded in the document shown below. Some of this issues have been resolved and some still need to be investigated further. Also, some things were documented that were not necessarily a problem but resulted in a board modification so they were documented here.
Functional Demo Materials
- Demonstrate 12V regulation on PMB.
- Demonstrate 24V regulation on PMB.
- Demonstrate working I2C communication to sensors on PMB.
- Demonstrate the ability to power other boards.
Plans for next phase
- Finish testing the PMB.
- Test the MPPT with the solar panel.
- Continue writing software for the PMB.
- Look into the GRSS.