This week the team continued to hustle towards the rapidly approaching 90% completion deadline.
During their weekly Tuesday meeting on West campus, the team had planned to test the power amp circuit Hunter had completed soldering. However, upon initiating the test, the team realized that the transducer seemed damaged.
A quick multimeter reading showed that the transducer was an open circuit. Further inspection revealed that the fragile voice coil was not properly terminated inside the transducer. Unfortunately, this could not be fixed. Hunter will conduct testing independently the next day.
Despite this minor setback, John was able to complete the soldering of the analog signal board (preamps/DAC output circuit).
The team met for a second time on Friday night to install the power amp into the device enclosure. All that remains of the enclosure is the Mic/Transducer Housing and Touchscreen integration.
John
This week John completed construction of the main device enclosure. This included the installation of the main power switch/connectors, 5-Pin XLR connector, cooling fan, and rearrangement of the internal layout and wiring. (See above)
John also completed adding the DAC output circuit to the preamp board.
John also began the process of programming the DSP. By creating multiple projects using slightly different elements, he hopes to more quickly arrive at a solution.
FxNLMS block based program with feedback elimination
MFxLMS Block based program. This is a powerful "all-in-one" function block for ANC applications.
John also completed construction and wiring of the transducer/mic housing.
Lastly, John made a post to the Analog Devices forums and established communication with a representative from Analog Devices to seek help with some sigma studio troubleshooting.
Hunter
As mentioned in the teams opening statement above, during the teams meetup for Tuesday at the West Campus, the new transducer that was to be used for testing was dead out of the box. Hunter went the following day to do independent testing to verify that the power amp worked at the West Campus's EET lab. John has the projects power supply, so for the bias voltages Hunter used the Triple Power Supply.
The video below is a quick video showing the modification that was required to use the Triple Power Supply so that it produces the +VCC & -VEE bias voltages. The teams power supply produces +-24V, and the triple power supply produces +-20V, which is close enough to get a good idea of how it will behave with the teams +-24V output.
The video clip below displays the output of the Power Amplifier now that it is soldered to a PCB. There was some expected clipping shown from CH1 (yellow) when the amplitude of the signal generator was raised above approximately 3.5 to 3.6Vp-p. Our team was aware that there would be clipping close to this range when the DAC/Power Amp Pspice simulations were conducted. This is also the reason the DAC output connections needed to be modified.
The tests today were done to verify that the PCB version of the Power-Amplifier is working properly and to analyze the behavior and themal temperature when driving the max output of the LM1875 power amplifier. Disregard the breadboard components in the background, as this was only used to place the Power Amplifier on a plastic surface.
While testing the power amplifier Hunter used his infrared thermometer to check the temperature of the amplifier and heatsink. The heat sink worked very well and neither the amp or heatsink went above 92°, even after testing several times for about 2 to 3 minutes for each test.
Updated the websites Weekly Minutes with Professor page:
A handle, stronger hinge, and screwed in rubber feet for bottom protection were added the drywall/stud sample that was originally made last week.
A quick video of the dry wall sample additions:
Updated the websites Lessons Learned page:
For the Touchscreen, John found a cover at Skycraft that Hunter modified for the screen to fit inside to fit inside:
