Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 42 | Position-Sound Accurate Electric Snare Drum |
Kadin Shaheen Oscar Li Tim Dager |
Aniket Chatterjee | design_document1.pdf proposal1.pdf |
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| Team Members: Tim Dager (timcd2) Kadin Shaheen (kadinas2) Oscar Li (hongyil9) Problem Modern electronic snare drums are unable to replicate the detail of sound that changes continuously based on how and where you strike an acoustic drum. They generally relegate hits to one of three zones: head, center, or rim, with some degree of velocity sensitivity. The issue with determining strike zones through dedicated zone sensors is a limited resolution sound profile. Our goal is to develop a digital snare that utilizes time difference of arrival (TDOA) with piezoelectric sensors to pinpoint drum strikes to a centimeter level of precision to realistically emulate the sound profile of an acoustic drum. Further positional detection improvements and low-latency benchmarks will be treated as stretch goals. Solution We will utilize three piezoelectric sensors with analog processing components feeding to an STM32 microcontroller to measure and calculate strike position. The piezos will be placed equidistantly from the center of the drum mesh and will detect the first arrival of a wave to triangulate the strike position. Signal processing will account for reflected waves from the rim of the snare drum as well as attenuation across the mesh. The STM32 microcontroller will be used for its DAC module, digital signal processing, and communication through USB as a MIDI device. The drum pad will divide into four subsystems including the piezo sensor array, analog pcb, MCU, and power subsystem. Solution Components Subsystem 1: Piezo Sensor Array A set of concentrically spaced, commonly available piezo vibration sensors will be mounted to an inexpensive single zone mesh drum. A minimum of three sensors are needed to perform the time difference of arrival (TDOA) algorithm, but more may be added (while maintaining concentricity) to allow for cross referencing if necessary. The placement of these sensors will mimic implementations of TDOA systems in similar applications. Subsystem 2: Analog PCB An analog preprocessing board will take inputs from each of the piezo sensors, and convert them into usable analog inputs in the range of the microcontroller. It will consist of an op-amp as an impedance buffer for each piezo, a voltage translator to align our analog signal with the specification of the microcontroller (0 - 3.3v for STM 32), and a clamping circuit to protect from voltage spikes. Subsystem 3: MCU (computation + data output) An STM32 with a 12 bit ADC will be used to accept the three analog signals, perform the TDOA algorithm to compute a positional estimate, and generate the appropriate usb signals as MIDI, that the user may use for triggering drums, or other purposes. Subsystem 4: Power The power subsystem will take input from a USB source and output correct voltage levels to the Analog PCB Subsystem and to the MCU. The device will be powered from a 5V USB input with USB-C preferred. A 3.3V onboard regulator will generate the primary logic and analog supply rail for the STM32 microcontroller and other 3.3 V compatible components. The subsystem will include input protection, local decoupling/bulk capacitors to maintain a stable 3.3V rail. If later component selection requires an additional power supply voltage for the analog subsystem, or other circuitry, an additional regulated rail may be added. Criterion For Success The drum must be capable of distinguishing between a minimum of 10 distinct radial zones, each of which may be mapped to different midi notes to confirm zone accuracy Drum pad USB device endpoint is recognized as a MIDI interface Net latency measured from impact time to USB handshake should be minimal enough to avoid causing an audio-tactile mismatch (delay between strike and sound) sensed by the player- roughly 40ms. |
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