Design Week 9: 3/7-3/14

Over the Spring break the team moved into overdrive to push the project along.

The team met during the week to test the power amp breadboard for expected functionality.

The breadboarded power amp worked! The board easily drives both a single transducer and a parallel pair. Power amp was powered by the +-24V supply with no issues.

1 Vpp input

2 Vpp input

4 Vpp input

5 Vpp input

Next Week's Agenda

• Install Power Amp

• Test Device Throughput from Mic to Transducer

• Finalize Prototype Device Enclosure/Construction

• Program DSP with ANC algorithm and conduct preliminary testing

• Test Bed Testing of Device

• 
  

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John

During the break John made several visits to skycraft to gather materials for the prototype housing and construction. Over the week he added shielding, standoff legs, and wiring to the prototype in order to give it a rugged and compact construction.

Enclosure with lid closed

Enclosure with power supply, preamp, DAC circuit, DSP, codec, and interconnections. All subsystems are shielded with grounded metal covers.

Both the analog and digital subsystems were soldered on perf-board and mounted in separate enclosures. While at skycraft, John found much smaller 10uF and 1uF capacitors that saved a lot of space in the final construction.

10uF

1uF

John was also able to establish analog to analog signal throughput from preamp input to DSP output!

Bench setup with preamp, adc, dsp, and dac.

John successfully programmed the DSP with the correct digital format (i2s), sample rate (192kHz), and inter device clocking.

100Hz sine through the DSP

Simple gain reduction program

Gain boosted to observe output clipping threshold (~2.23 V pp)

Bode Plot for device throughput.

Group Delay at 50Hz (~100uS)

Group Delay at 300Hz (~100uS)

Layout planner for the preamp/DAC output circuits.

Bode Plots for both channels of the constructed preamp.

Passband both channels (1dB per div vertical)

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Hunter

The power amplifier was traced, placed, and soldered to a PCB after a successful day of testing the breadboard version.

Beginning of PCB placement of Power Amp:

Both picture below are just before soldering to PCB verifying size and placement:

Soldered with large heat sink screwed onto power amp with thermal paste:

On Monday the team meet at the west campus to test power amplifier but the transducer that was brought for testing was new and expected it to work just as well as all the others but ended up being dead out of the box.

A digital multimeter was used to check for continuity and showed that the transducer was an open circuit. Carfully opening the transducer showed that the thin voice coil was not connected and could not be fixed.

Hunter will test the amplifier independently, the following day, on Tuesday. Results will be posted in the, Week 10, progress log.

This week the drywall/stud sample was also completed:

Bottom, before it was lightly sanded on all sides:

Hinge and latch was added for easy and secure access inside for testing with and without insulation:

An addition to last weeks ANC Display, a portrait layout, including buttons, was also made this week, since we may use the display in a portrait layout rather than a landscape layout. So either option is possible.