Underground, Under Budget
During this internship I designed a preamplifier for soil ecoacoustics. The preamp is designed to be used with a piezoelectric microphone and it is built with low-cost components. A documentation website was created to share the design and the code with the community.
Year
2024
Duration
16 weeks
Type
Individual
Tools
KiCad, Teensy, Daisy Seed, electronics, C++, Astro.js
Keywords
electronics, signal processing, prototyping
Check out the documentation website!
The documentation website contains in-depth information about the project, including the schematics, the code and the instructions to build your own preamp.
Outcome
The outcome of the project is a breadboad prototype and design proposal for a low cost preamplifier circuit. Information about the project and the design files are available on the documentation website.
Signal processing prototype
The breadboard prototype is a proof of concept that demonstrates the functionality of the preamplifier. It is built with throughole components for quick assembly and testing. The design features a split rail stage that takes the 6V from the batteries and turns it into a ±3V supply.
A breadboard prototype of the preamplifier circuit built with throughole components.
Recorder prototype
The recorder prototype is built with a Teensy 4.1 and an I2S ADC that uses the PCM1802 IC. The Signal Processing Prototype is connected to the audio input of the ADC board, which sends data to the Teenzy 4.1 to record the output to a microSD card.
A breadboard prototype of the Teensy 4.1 connected to a analog-digital converter with I2S.
Documentation website
The documentation website contains information about the design process, the schematics of the preamplifier and the code that runs on the Teensy 4.1. It also addresses common issues that I run into during the design process and how I solved them. The website is built with Astro.js and the content is written in Markdown to make it easy to update, export and share.
Homepage of opensoilacoustics.org
Tasks
During the internship I worked on the design of the preamplifier, the documentation website and the code that runs on the Teensy 4.1 and Daisy Seed. The preamp is designed to be used with a piezoelectric microphone and it is built with low-cost components. The documentation website was created to share the design and the code with the community.
Circuit and PCB design
The circuit was designed and simulated in KiCad befire building each physical prototype. KiCad was also used to design a PCB, which is currently still being tweaked to improve the performance of the preamp.
PCB design of the preamplifier circuit made with KiCad.
Testing and prototyping
Given my lack of experience with electronics, much of the work was using prototypes to test out ideas and learn about essential concepts. Prototyping was also used to test the performance of the circuit in a lab setting. The preamp was tested with DIYed contact microphones built with piezoelectric elements.
Breadboard prototype of the preamplifier circuit and the Teensy 4.1 used to test audio recording.