Power Detailed Design
Table of Contents
Feasibility: Prototyping, Analysis, Simulation
Zero Pressure BalloonOne source said that zero pressure balloons are made from very thin (7.5 micron) plastic sheet. Another source has that they are made of a 0.8 mil single layer of LLPDE film. This is a similar material to a grocery bag and will allow most of the solar energy to pass through. Will preform experiment with Zero Pressure balloon material when sensor becomes available.
More information can be found at the resources below.
Key Component Selection
MicrocontrollerThe MSP432 will be used for the PMB to keep consistency throughout the payload. The BioX Cell board is also using this controller.
|Device||Reference Designator||I2C Address|
|Solar Panel Power Sense||U4||100 0000|
|24V Power Sense||U5||100 0101|
|On Board Temp Sensor||U6||100 1000|
|Battery Power Sense||U7||100 0001|
|Battery Temperature Sense||N/A||001 1000|
|Output Current Monitor 1||U8||001 0000|
|Output Current Monitor 2||U9||001 0010|
12V RegulatorA Buck-Boost topology was chosen for the 12V regulator because the battery voltage can vary between 9V and 12.6V. A buck-boost allows to utilize the full battery voltage range.
3.3V RegulatorThe 3.3V regulator is the same one that is used on the CBOB. The 3.3V regulator is need to supply power to the microcontroller and sensors.
24V RegulatorA boost topology was chosen for the 24V regulator. This will be stepping up the 12V regulated voltage to 24V to power the motor drive. The converters input was chosen to be the regulated 12V to ensure that the 12V line will always come up before the 24V line.
Component Selection Design FileAll calculations necessary for the design were performed using MathCAD. A PDF of the file is linked below.
Drawings, Schematics, Flow Charts, Simulations
Detailed Power System Block Diagram
Power Management Board Schematics
A PDF of the entire schematic is linked below.
Power Management Board PCB LayoutDetailed Design Documents/Power/Top_Layer_PCB.pdf Detailed Design Documents/Power/Layer2_PCB.pdf Detailed Design Documents/Power/Layer3_PCB.pdf Detailed Design Documents/Power/Bottom_Layer_PCB.pdf Detailed Design Documents/Power/All_Layers_PCB.pdf
Bill of Material (BOM)
The bill of material for the PMB PCB components is shown below. The total cost of components for one board is $129.26. The actual price for components may be less due to decreases in price with higher quantities of parts and requesting free samples when possible.
The Excel document for the PCB component BOM is linked below.
The bill of materials for the entire power system is shown below. The total cost of the power system is estimated to be $685.25. This is over the $550 budget for the power system.
The Excel document for the Power System BOM is linked below.
Power System Engineering Requirements
ER35: Turn on voltage Come Alive Voltage Test: Slowly bring up the input voltage on the PMB while monitoring the 12V output to determine the come alive voltage with no load and full load
ER36: Turn off voltage Stay Alive Voltage Test: Slowly bring down the input voltage on the PMB while monitoring the 12V output to determine the stay alive voltage with no load and full load
ER37: 12V Regulation, ER38: 12V Regulator Efficiency 12V Regulation / Efficiency Test : The PMB input power and output power will monitored with various input voltages and various load currents
ER39: Voltage Overshoot from load step The PMB will be power with 12V and the load will be stepped from min to max and max to min
ER40: Ripple Voltage Monitor the ripple voltage on the 12V output with min, typ, and max load conditions
A link to the full test plan document is included below.