P17316: Light Rail
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

The team planned to

The team accomplished these goals and started working towards a couple of next phase goals. The cable manager was outfitted with holes so the electrical team could begin assembling the LED sequence. The electrical team is also working on cable stress relief options.

Test Results Summary

Software

A test was done to check that the frequency requested in the code matched the frequency exhibited in the test set of LED lights. The testing procedure timed a sequence of 8 LED lights as they blinked at an intended frequency of 5 Hz. The accuracy of measurement was limited by the precision of the stop watch (10 ms) and human reaction time.

The results of the test are shown in the table below. Based on the results, even with experimental error considered, the system is displaying measured results within 10% error of the target frequency.

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Test 2 was conducted to reduce the impact of error on the measurement. By increasing the length of time measured, the errors incurred while starting and stopping the stopwatch were a smaller percentage of the overall data. The error for this measurement was less than 1% of the intended value.

Mechanical

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The above picture shows a 6 foot member of the proposed light rail deflecting under gravity. Both ends have a clamped boundary condition. The results show a small deflection (0.004in) due to gravity. With the addition of the brackets at each connection location, the deflection at the connections will be severely limited.

The below picture shows the stresses experienced in a 6 foot member under a loading scenario. The member has a left side symmetry boundary condition and a right side clamped boundary condition. The loading scenario is 50 lbs of downward force applied at each arrow location simultaneously. This is to simulate accidental weight being applied to the structure. The results show the beam will yield at the clamped end. However, it is our belief that the support structures will give out and fall before a loading scenario causes the light rail to yield. Currently, we are working to find the maximum load the rail will support without yielding.

This analysis provides the necessary evidence to verify that the proposed light rail will be sufficient for our design.

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The below picture shows the stresses experienced in a 6 foot member under a loading scenario. The member has a left side symmetry boundary condition and a right side clamped boundary condition. The loading scenario is a 20 lbs local load of downward force. (Gravity is also being applied.) This is to simulate accidental weight being applied directly at the connection point. This is the max load that can be applied at this location to prevent any yield in the light rail. Again, we believe the supports will tip before a loading scenario causes the light rail to yield.

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Electrical

The functionality of each LED circuit was tested using a DC power supply and a function generator set to a 1 Vp-p square wave with a 0.5 V DC offset. The frequency was set a 1 Hz. Each circuit was connected as follows:

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When the connections were made, a LED that turned on was considered functional. Any LED circuits that didn't turn on were corrected.

Risk and Problem Tracking

As a team, our biggest risk is not completing the project by our "Spring Training" deadline. We have worked on a plan to meet that deadline (or as close as possible) during this phase. If we cannot have a fully operational prototype by the end of the month, we would like to be able to give Dr. Edmunds something with partial functionality while we work on the rest of the features.

Risk Management Documentation

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Problem Tracking

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The full problem tracking document is located in our directory.

Functional Demo Materials

Mechanical Build Progress

Mechanical Subsystem Build Progress

Click here for our collection of CAD Models.

Software Testing

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Video Link for Software Test. Here is another video using 8 Lights.

Electrical Build Progress

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Above is an image showing two LED circuits built on prototype board. They are ready for installation in the cable manager. The completed circuits will be showed and demoed at our subsystem build and test review.

Plans for next phase

  1. Mechanical: The manufacturing of parts will be finished and the Light Rail will be assembled at least once. The documentation package and testing procedures will be started.
  2. Electrical: The LED circuits will be assembled in the cable manager. The electrical portions of the documentation package will be started as well. Electrical tests will be started.
  3. Software: The LED control program will be completed and tested. The GUI program will be in progress.

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