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Subsystem Build & Test

Table of Contents 1 Team Vision for Subsystem Level Build & Test Phase 2 Custom PCB Update 2.1 2/28/17 Update: 3 Mechanical Side Update 4 Test Results Summary 5 Risk and Problem Tracking 5.1 Risk Management 5.2 Problem Tracking 6 Plans for Next Phase 6.1 Team Plans 6.2 Individual Plans

Team Vision for Subsystem Level Build & Test Phase

Summarize: Since our last design review, we have worked on the structure and our custom PCB. We have finished the custom PCB component placement and layout; it has also been reviewed. We are going to order the board and components.

We have also done more testing. The OSD module has been controlled with the Rasperry Pi. We have received 2m transmissions from the Pi with the METEOR Lab equipment. The Pi has received APRS packets. We have tested the 2m transceiver subsystem (prototyped) and the 70cm ATV transmitter subsystem together with the diplexer and antenna.

Since the last update the metal side structure has begun being machining, and roughly will be complete by end of week 6. The current model will be the primary system testing platform for the upcoming reviews. As such an order will be placed for secondary materials that will constitute the flight ready platform. See mechanical side tab for further details.

Custom PCB Update

We have finished designing our custom PCB. We will be ordering the board and components.

The updated schematic can be found here: Main COMMS Board Schematic

The updated custom PCB BOM can be found here: Main COMMS Board BOM

Here are some images of the layout:

Here is a view of the panel gerbers (two copies of the board):

2/28/17 Update:

We have ordered a panel from Advanced Circuits with 2 copies of the board on it.

Our gerbers can be found here: zipped gerbers

Their generated plots can be found here: Advanced Circuits Plots

Mechanical Side Update

• Since the last review a handful of new mechanical side components have been decided on - being developed and machined that is. They are as follows:
  • APRS Mount: With the requirement for the APRS to be positioned at the top of the platform a "holding device" is required in order to do so. The device will be a lightweight 3D printed "cubicle" designed simply to hold the APRS at the top. In the spirit of MSD, the current plan is to use a fellow MSD team's project (their printer) in order to print it. It uses a feedback heat control system that aims to improve printing quality.
  • Antenna Ground Mounts: To connect the antenna grounds to the platform cage arms, a series of hinges will need to be made to allow flexibility upward but not downwards for various reasons such as impact and assembly. As the grounds will be made from aluminum we are proposing using a combination of stock metal hinges and the necessary 3D printed coupled components. Design is being considered. The back-up plan is to utilize umbrella arms as they are already flexible.

• The following have not yet been account for in the system package:
  • NTSC Cameras and Mounts: Item was recently changed, will be incorporated upon final decision of which component to use.
  • Motor Mount: It was only recently confirmed that an additional mount would be required for the motor - to preserve the polyethylene structural integrity. DAQCS team side is working on mount development.
  • Motor Mount Level Aluminum: To be completed once motor mount design is complete.
  • Antenna Ground Hinges: In progress.
  • Wires: Work in progress for both teams.
• Balloon Neck Plug
  • Met with James, plug designer and fabricator, and he agreed to make an additional plug so long as the stock material is provided (1.5in dia, 6in length, estimated cost: 20$). The estimated manufacturing time on this is two days. Electronic holes are included in the design - for potential cutdown components.

As stated previously, the current version of the cage will be primarily a test system, namely for the reaction wheel. The following highlights current aspects of the cage divided by part:

• Upper Disk - 70% complete, only tooling left is to etch of the inner and outer circles.
• Upper Arms - Not yet started, to be complete at end of Week 6.
• Lower Arms - 90% complete, only tooling left is to grind ends down to dimension. Because of bending, the individual arm pieces were cut longer than dimensions, thus the need for additional tooling. It should also be noted that the upper sections of each of the arms are warped. This is due to machinist error, as there was a small arc at the end of the first cut piece and the error propagated to each subsequent piece. The error at the time of machining was not deemed critical as the two holes of the section are independent of each other. For the test model this is a non issue, and furthermore may not be an issue regardless. This section of the arm was slated to be tested for bearing stresses and as such would make an excellent test piece - incorporating some imperfections.
• Lower Disk - 70% complete, only tooling left is to etch of the inner and outer circles.

Final manufacturing of the polyethylene layers has not begun as components are being finalized and the layers themselves are more so integration functioning. Aside from that the two component mounting methods have been finalized as such:

• Screws & Embedded Nuts - After testing a variety of polyethylene adhesives Sydney of DAQCS team found that hot glue worked well without burning the polyethlene, so long as used with careful application - avoiding bubbles. This enables upright components to be mounted directly into the layer boards via nuts adhesed into the layer.
  • ATV
  • RasPi Boards
  • GRSS Board
  • Buzzer

• Screws & Through Hole Nuts - With components that will be hanging there was worry that they would break off embedded nuts from the layers and so the placement of the components was changed so that through holes could be applied to the layers at the appropraite positions. This allows the electronical components to anchor firmly to a layer without issue.
  • Custom PCB COMMS
  • Custom PCB DAQCS
  • OSD

• Shear Strips - Perhaps the most interesting method of mounting are the shear strips, or wall haning strips. Designed for shearing appilications they make an excellend adhesing method for the heavier system components as they will constantly be in shear (i.e. back and forth rotation). The shear strips can be embedded into the layer so that components such as the batteries can lie square with the normal contour of the surface allowing the electronic to undergo thermal management from the foil surface.
  • Duplexer
  • Motor Battery
  • 70CM Battery
  • 2M Battery
  • Radio
  • APRS Battery
  • APRS
  • GPS

• Combination of Shear Strips and Through Hole Nuts - Some components due to their positioning and characteristics require a more thorough mounting system. The RasPi's however utilize this method simply for redundancy, as they are outer most. The motor controller howver absolutely requires as much redundant mounting as possible. With it being among the heaviest of components, it is placed it a less than optimal position, hanging. The native screw mounts for the controller require through holes to support the weight. In the case of a screw failure, or polyethylene failure two shear strips have been placed on the controller surface.
  • RasPi Cameras
  • Motor Controller

• Other
  • Motor (In development by DAQCS and COMMS)
  • Foil (Adhesives)

Test Results Summary

See the test plans on the Build & Test Prep page.

We have performed the following testing:

• Tested 70cm ATV transmitter subsystem and 2m transceiver subsystems (prototypes) operating at the same time with the diplexer and antenna
• Tested receiving APRS packets on the Pi Zero with our 2m transceiver subsystem prototype
• Tested transmitting with 2m transceiver subsystem prototype (received and decoded packets with METEOR Lab equipment)
• Tested controlling the OSD with Raspberry Pi Zero and RS232 level converter
• Tested 70cm ATV transmitter subsystem with video mux eval board

Risk and Problem Tracking

Risk Management

The updated working document can be found here.

Problem Tracking

Here is our updated problem tracking table:

Here is a pie chart with our updated progress on these problems:

The updated working document can be found here.

Plans for Next Phase

Team Plans

Our Gantt chart working document can be found here: MSD II Gantt Chart

A list of team tasks for the next phase can be found here.

Individual Plans

• Connor's Phase 7 Individual Plan
• Ian's Phase 7 Individual Plan
• Adam's Phase 7 Individual Plan
• Matt's Phase 7 Individual Plan

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