Project

# Title Team Members TA Documents Sponsor
3 Heterodyne Bat Detector
 BILL Waltz
Evan McGowan
Kyle Jedryszek
 Gayatri Chandran
Team Members:
- Bill Waltz (wwaltz2)
- Kyle Jedryszek (kaj5)
- Evan McGowan (evandm2)

# Problem:

There is a need for American-made and sold handheld heterodyne bat detectors. There are some American bat enthusiasts who dislike the bat detectors that plug into phones or tablets, like the ones from Wildlife Acoustics, since the sound produced is not as high-quality as a standard heterodyne. Also, these models cost $300+. The most popular heterodynes are currently produced and sold in the UK and Australia. Specifically, Dr. Joy O'Keefe is in demand of a high-quality, mass-produceable device for the purpose of providing several groups of people with a bat detecting device for Bat Walks at the Central Illinois Bat Festival.


# Solution

A handheld device with a microphone, capable of detecting frequencies between 15kHz-100kHz, which will be amplified before being heterodyned with a mixer circuit. The frequency to be mixed with is controlled by a large dial (with illuminated frequency labels) on the front of the device. The sound will then be amplified and output via quality speakers. The device will also have a power button, a volume dial, a 3.5mm auxiliary port for headphone use, and be powered by AAA batteries. Finally, what might set this apart from every other bat detector is that this model will have stored, prerecorded sound bytes that can be played so that first-time users can know what to listen for.


# Solution Components

## Ultrasonic Receiver

To first receive the signal, we will employ an ultrasonic transducer, likely to be the most important and expensive part of the product. Transducer options include Syntiant’s SPVA1A0LR5H-1 microphone, readily available on DigiKey, since it has a frequency rating well into the LF spectrum. A pre-amplifier using op-amps like the TLV9052/ADA4097 will amplify the desired signal, followed by a high-pass filter to remove low-frequency noise below 20kHz.

## Heterodyne

To mix the ultrasonic signal down to baseband, we will employ a double-balanced mixer like the SA612A or MC1496, producing the internal oscillator signal as well. This heterodyned signal is then amplified with another op-amp circuit and passed through to a speaker. Finally, our leading choice for speaker is the Taoglas SPKM.23.8.A: a thin, ~1-inch diameter speaker which will fit nicely into a handheld device.

## Bat Sound Playback

Pre-recorded audio bytes from other heterodyne bat detectors will be programmed onto a flash memory module, size somewhere between 32K-512K, that can be accessed by a microcontroller. An ATTiny85 is our MCU of choice, as its availability, low cost, and speed satisfy our needs for this project. When the device is on, and the user presses a button labeled “Demo” on the device, one of the recordings will play from the speaker or audio jack, preceded by an announcement of which species of bat they are hearing. The programming for the MCU and flash memory will be done via an external programmer (such as the USBasp), with the audio data dumped directly into the external flash storage.

## User Interface

The UI will consist of a 3D-printed handheld chassis for the device. The chassis will contain a power button (or switch) which will either be mechanically or electrically connected to the main board, and an adjustable volume knob. The device will have a dial (labeled with both frequencies (in kHz) and common bat call ranges) to adjust a potentiometer to change the frequency of the onboard oscillator. There will also be a dim, non-invasive red or green light that will shine on the frequency dial, such that the user has the ability to read the dial in the dark. The bottom of the device will have a 3.5mm auxiliary audio port for headphone listeners.


# Criterion For Success

Our product must accomplish the following objectives to be considered successful:

Total production cost below 50USD including casing

Device must be tunable between 15kHz and 100kHz frequencies using onboard tuner, testable using Dr. O’Keefe’s Ultrasound Calibrator

Battery life (rechargeable or otherwise) lasts the length of (at least) one bat walk (1-2 hours)

Volume control is tunable from muted to more-than-noticeably audible

Selected bat sounds must be audible through speaker when played

When an ultrasonic source radiates sound, the device must downconvert it to audible frequencies and play it through the onboard speaker

Four Point Probe

Simon Danthinne, Ming-Yan Hsiao, Dorian Tricaud

Four Point Probe

Featured Project

# Four Point Probe

Team Members:

Simon Danthinne(simoned2)

Ming-Yan Hsiao(myhsiao2)

Dorian Tricaud (tricaud2)

# Problem:

In the manufacturing process of semiconductor wafers, numerous pieces of test equipment are essential to verify that each manufacturing step has been correctly executed. This requirement significantly raises the cost barrier for entering semiconductor manufacturing, making it challenging for students and hobbyists to gain practical experience. To address this issue, we propose developing an all-in-one four-point probe setup. This device will enable users to measure the surface resistivity of a wafer, a critical parameter that can provide insights into various properties of the wafer, such as its doping level. By offering a more accessible and cost-effective solution, we aim to lower the entry barriers and facilitate hands-on learning and experimentation in semiconductor manufacturing.

# Solution:

Our design will use an off-the-shelf four point probe head for the precision manufacturing tolerances which will be used for contact with the wafer. This wafer contact solution will then be connected to a current source precisely controlled by an IC as well as an ADC to measure the voltage. For user interface, we will have an array of buttons for user input as well as an LCD screen to provide measurement readout and parameter setup regarding wafer information. This will allow us to make better approximations for the wafer based on size and doping type.

# Solution Components:

## Subsystem 1: Measurement system

We will utilize a four-point probe head (HPS2523) with 2mm diameter gold tips to measure the sheet resistance of the silicon wafer. A DC voltage regulator (DIO6905CSH3) will be employed to force current through the two outer tips, while a 24-bit ADC (MCP3561RT-E/ST) will measure the voltage across the two inner tips, with expected measurements in the millivolt range and current operation lasting several milliseconds. Additionally, we plan to use an AC voltage regulator (TPS79633QDCQRQ1) to transiently sweep the outer tips to measure capacitances between them, which will help determine the dopants present. To accurately measure the low voltages, we will amplify the signal using an JFET op-amp (OPA140AIDGKR) to ensure it falls within the ADC’s specifications. Using these measurements, we can apply formulas with corrections for real-world factors to calculate the sheet resistance and other parameters of the wafer.

## Subsystem 2: User Input

To enable users to interact effectively with the measurement system, we will implement an array of buttons that offer various functions such as calibration, measurement setup, and measurement polling. This interface will let users configure the measurement system to ensure that the approximations are suitable for the specific properties of the wafer. The button interface will provide users with the ability to initiate calibration routines to ensure accuracy and reliability, and set up measurements by defining parameters like type, range, and size tailored to the wafer’s characteristics. Additionally, users can poll measurements to start, stop, and monitor ongoing measurements, allowing for real-time adjustments and data collection. The interface also allows users to make approximations regarding other wafer properties so the user can quickly find out more information on their wafer. This comprehensive button interface will make the measurement system user-friendly and adaptable, ensuring precise and efficient measurements tailored to the specific needs of each wafer.

## Subsystem 3: Display

To provide output to users, we will utilize a monochrome 2.4 inch 128x64 OLED LCD display driven over SPI from the MCU. This display will not only present data clearly but also serve as an interface for users to interact with the device. The monochrome LCD will be instrumental in displaying measurement results, system status, and other relevant information in a straightforward and easy-to-read format. Additionally, it will facilitate user interaction by providing visual feedback during calibration, measurement setup, and polling processes. This ensures that users can efficiently navigate and operate the device, making the overall experience intuitive and user-friendly.

# Criterion for Success:

A precise constant current can be run through the wafer for various samples

Measurement system can identify voltage (10mV range minimum) across wafer

Measurement data and calculations can be viewed on LCD

Button inputs allow us to navigate and setup measurement parameters

Total part cost per unit must be less than cheapest readily available four point probes (≤ 650 USD)

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