Subsystem Build & Test
Table of Contents
Team Vision for Subsystem Level Build & Test PhaseDuring this phase, the team wanted to finish as much of the subsystems as possible. The largest hurdle for the team is PCB design. This is still currently underway; however, they are nearly complete and will be ordered within the next phase.
Another expectation for this stage was to continue to work on the reaction wheel. The motor was able to be hooked up and controlled by an Arduino. The motor was driven by a PWM signal, first from a function generator and later generated by the Arduino. The motor, with its rotating rotor housing, demonstrated the ability to act as a reaction wheel up. Moving forward, the MSP430 and IMU will be connected to get more test results.
The GRSS has been tested for this phase and will be shown as a functional demo during the design review. It works well and after measuring prototype's current draw, it may last approximately 48 hours.
Custom PCB Update
GRSSGRSS during this phase went through the layout phase of the PCB process. The schematic was only updated with minimal changes after full prototyping of the design. Therefore, some of the work was on ensuring the part packages were satisfactory for location where the boards will be fabricated and that the imported packages didn't have any mistakes. The rest of the work was in placement of all the components while trying to minimize board dimensions and then manually routing each all signals in a best practices manner. One big change to the board after review was the addition of two drilled holes of 5mm diameter to utilize tyrap (zip-ties) to secure the battery throughout the duration of the flight to increase the probability that the platform will be found successfully after launch. This was a concern due to the weight of the battery being greater than the weight of the board.
Quick List of Updates for GRSS
- Added Test points
- Update all packages to have minimum silk screen width and correct dimensions/layers after import
- 0805 Components
- Schematic update for LED series resistor / Bypass Caps
- Zero ohm resistor for measuring current sunk through power FET
- Placement of all parts with mounting holes
- Manual routing
- Power / GND Planes
- Silkscreen aesthetics with logos
- Updated trace width for current for LEDs / Power FET
- Added heat sink pad/wing for Power FET
- Added tyrap holes to support battery
- Board Dimension updates for paneling
A working document of the BOM can be found here
A working document of the Schematic can be found here
RasPi HAT and Balloon Sensor Panel
Risk and Problem Tracking
- A working document of Risk Management can be found here: Risk Management
- A working document of Problem tracking can be found here: Problem Tracking.
Functional Demo Materials/Testing
SummaryThe GRSS was fully prototyped utilizing a breadboard, 9 LEDs, the buzzer and all parts in the BOM where jelly bean parts were non-SMD type and LDO and 555 Timer were soldered to breakout boards.Total current sunk through Power FET was 31mA, giving the prototype an estimated 48 hours assuming perfect 50% duty cycle and assuming the battery has a full 750mAH through entire flight. During this demo, the Buzzer was heard with an average of 102.5dB utilizing iPhone Decibel 10th app and the 9 LEDs together generated around 4000 Lux utilizing iPhone Light Meter app.
Demo VideoGRSS Full Prototype Demo
Reaction WheelDuring the past couple weeks, the motor and motor controller platform have been tested. Two videos may be seen that show two parts of the testing: regulation tuning (Regulation Tuning video) and actual testing where the entire platform may be seen to be moving (Testing Video).
The system that has been tested up to this point is composed of the Arduino, the motor controller, the motor itself, the 6A power supply found in the Electronics Lab, as well as a platform that simulates approximately 41% of the overall desired inertia.
In the picture above, the end test result of the regulation tuning might be seen. There are three tests that the Maxon Motor Software (called ESCON Studio) does, which provides the two plots seen above.
The test results from a simple PWM signal may be seen above. The current that is being required of the system, the PWM signal, and the actual speed of the motor can all be seen above on the plot.
While developing the code and setting up the software/hardware, a user guide for the motor and motor controller has also been developed. The current guide may be seen here. It is still being updated and added to, and therefore, is a draft.
There are several issues that will be looked into for the next phase. The largest problem being seen right now is the possibility of current flowing back into the battery due to a large change or reversal in speed from the motor. After speaking with Maxon Motors, there are several options available to the team. The options include: a shunt regulator may be inserted into the system, an additional capacitor be added into the system, or the acceleration of the motor be turned down. The shunt regulator is a very expensive option. It is hoped that the acceleration would not have to be decreased extremely, as this then lowers the amount of torque that can be outputted by the motor. The added capacitor is an option that will be looked into in the next phase.
Plans for next phaseTeam Gantt Chart
Steven Giewont's Three Week Plan: Steven's Goals.
Lincoln Glauser's Three Week Plan: Lincoln's Goals.
Sydney Kaminski's Three Week Plan: Sydney's Goals.
Chris Schwab's Three Week Plan: Chris's Goals.