Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 3 | Heterodyne Bat Detector |
BILL Waltz Evan McGowan Kyle Jedryszek |
Gayatri Chandran | design_document1.pdf proposal1.pdf |
Dr. Joy O'Keefe |
| 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 |
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