P16214: Bicycle Power Meter

Subsystem Build & Test

Table of Contents

The goal of this phase was for our MSD team to continue testing on our subsystems before putting the subsystems together and testing them as an integrated system. This page shows our team's progress as we continued testing each subsystem.

Team Vision for Subsystem Level Build & Test Phase

Our team vision and goals for the subsystem build and test phase was to continue testing of the power meter at the subsystem level. Any issues that we had with testing during the previous phase will continue to be tested and fixed during this phase. Our MSD team also plans to begin integrating the subsystems together to start moving closer to our finished design and product. The more items we continue testing and begin to test will mitigate our risk items as we are focusing on our higher risk items.

Test Results Summary

Our MSD team continued tests from last phase while we continued to make progress with our tests we have not yet fully completed some of the tests although they are nearing completion. For this reason our test plan tracker has not changed from last phase.

Test Plan Tracker

Test Plan Tracker

The original and live documents for the test plan and the test plan tracker can be found as the Test Plan Document and the Test Plan Tracker. With this test plan tracker the following sections go into further detail with the tests that are being conducted during this phase.

Strain Gauge Amplifier Circuit

Our team continued to test the strain gauge amplifier circuit to solve the issues we were facing from the last phase. The issues with the amplifier circuit were with the etched PCB that our team created.

public/Photo Gallery/Amp PCB_With Components_1.JPG

Using the etched PCB the output of the amplifier was producing a voltage that was much higher than expected. We believe that the cause of this high output voltage was due to small resistance increases caused by the etched PCB. Since the signal from the strain gauges that is getting amplified is such a small signal, the smallest change in resistance will cause a very large change in the amplified output signal voltage. Since the strain gauge amplifier circuit worked correctly on the breadboard but not on the etched PCB our team decided that we would try using a through-hole prototyping PCB. We decided to test on the through-hole prototyping board because it is an intermediate step between the breadboard and the PCB. This would allow us to test any issues that we would find at the intermediate stage. Our team populated the components on the through-hole PCB and soldered them together.

public/Photo Gallery/Through_hole PCB.jpeg public/Photo Gallery/Populated Through_hole PCB.jpeg

In the images shown above, the image on the left shows what the through-hole prototyping PCB looks like. The image above on the right shows the through-hole PCB after it had been populated with the components. All of the components were populated and the necessary wired connections between pins of the components were soldered together on the back of the PCB. After completing soldering the components together on the through-hole PCB it was then tested to verify if it was producing the correct expected results. Upon testing the circuit it was discovered that this prototyping PCB also produced incorrect results similar to the etched PCB. This led our team to believe that the added resistance to our circuit was caused by the thick wires used connect the pins of components as well as the excess solder that may have been used while soldering the components together.

After some thought on various solutions to solve this issue our team decided that we would have a printed circuit board made by a PCB manufacturer for our strain gauge amplifier circuit. Our team used a software called ....... to create the design of the PCB. The following image shows the circuit board layout that was created using the software:

public/Photo Gallery/PCB Circuit Schematic.png public/Photo Gallery/PCB Circuit Layout.png

The image above on the left shows the circuit schematic that was created using the software. This circuit was needed to assist in creating the circuit board layout that is shown above on the right. After creating the circuit board layout the file was then sent to the manufacturer to be produced and sent back to us with a lead time of about a week and a half to two weeks. Our team has since then received our manufactured PCB which is shown below:

public/Photo Gallery/Manufactured PCB.jpeg

It can be seen in the image above that this PCB has much thinner traces connecting the pins of the components which will hopefully solve the resistance issue that we are seeing. Next our team plans to populate the PCB and test it to verify that it will work as expected.


After the shut down issue with the accelerometer was solved by making a precaution in the code our team was able to test the code for the accelerometer. Our team initially had written our own code to measure the rpm of the bike however, we were having issues with our code. This led our team to look for examples of code that had been used to measure rpm using an accelerometer. Our team was able to write a new code based off of the example code that will allow us to measure the rpm of the accelerometer that will be seen as it sits in the spindle of the crankset. Our team was able to verify that we are getting values for the rpm that seem fairly accurate however we are in the process of designing a test that will be able to spin the accelerometer at a known rpm to verify that the accelerometer does in fact give the correct value of rpm that is to be expected.

Bluetooth Communication

Our team had started the process of writing and testing code that would be use for the BLE communication to send information from the Bluno Nano microcontroller, which will be placed on the bicycle, to the Bluno microcontroller which will be used during testing and also as a backup in case we aren't able to get the smartphone app working in time for ImagineRIT. During our testing of the wireless BLE communication our Bluno had stopped working for unknown reasons which didn't allow us to finish our testing. Our team has ordered two more Bluno Nano microcontrollers and we are waiting to receive them before we can continue testing the wireless BLE communication.

Smart Phone App

During this phase our team had also started preliminary smartphone app development. Our team was able to create a simple layout for the app and are continuing to develop the app to receive and process information from the microcontroller. The following images shown below show the rough preliminary layout of the smartphone app that our team has created so far:

public/Photo Gallery/App Layout_1.png public/Photo Gallery/App Layout_2.png

Our team, having no smartphone app development experience prior, feels confident of our abilities to develop the app after our initial experiences with creating the app layout.

Risk and Problem Tracking

As our MSD team continued our testing we revisited our risk management tracker. The following image shows our updated risk assessment:

public/Photo Gallery/Risk Management_3-16-16.JPG

The only item that has changed is item number 1. The likelihood of this item has been increased from a 1 to a 2 because although we are confident that our microcontroller can communicate through the BLE communication to the Bluno microcontroller we have not yet tested if the microcontroller will communicate successfully to the smartphone app. Due to this uncertainty we have increased our likelihood of this occurrence.

Our team also continued to update our problem tracking document as we continued our testing during this phase. The following image shows the problem tracking document:

public/Photo Gallery/Problem Tracking_3-16-16.JPG

As it can be seen from the problem tracker above, we have resolved our accelerometer issue but another issue has arose with the strain gauge setup that we are using.

The original and live documents for both the risk assessment and the problem tracking can be found in the MSD II Documents sub-folder.

Functional Demo Materials

Our MSD team is continuing to conduct our tests for this phase. The following link is for the Test Plan Document which will show the tests that are planned to be conducted as well as the tests that are being conducted and some of the results that have been obtained from those tests. Our MSD team does not have fully analyzed data at this point in the project although we plan to have the data obtained in the next phase.

Plans for next phase

As our MSD team completed this phase we were still left with some outstanding issues that arose as a result of our testing of the subsystems. This allowed our team to come up with a list of plans we hope to accomplish during next phase mainly dealing with expediting our outstanding tests to complete them and get our team back on schedule to complete our final design by ImagineRIT. The list of plans for next phase are as follows:

Home | Planning & Execution | Imagine RIT

Problem Definition | Systems Design | Subsystem Design | Preliminary Detailed Design | Detailed Design

Build & Test Prep | Subsystem Build & Test | Integrated System Build & Test | Integrated System Build & Test with Customer Demo | Customer Handoff & Final Project Documentation