Digital Strobe Tuner. w/ On stage Display

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1 Page 1/7 # Guys EEL 4924 Electrical Engineering Design (Senior Design) Digital Strobe Tuner w/ On stage Display Team Members: Name: David Barnette dtbarn@ufl.edu Phone: Name: Jamie Lin jlquads@ufl.edu Phone:

2 Page 2/7 Table of Contents Project Abstract 3 Introduction 3 Features Technical Objectives Division of Labor Table 1: Cost Estimate 6 Figure 1: Concept of the design 3 Figure 2: Hardware Diagram 5 Figure 3: Software Diagram 5 Figure 4: Gantt Chart 7

Page 3/7 Project Abstract: Our project s purpose is to digitally simulate the behavior of an analog strobe tuner. The tuner will take an audio line input and send it to the microprocessor s ADC.

3 Page 3/7 Project Abstract: Our project s purpose is to digitally simulate the behavior of an analog strobe tuner. The tuner will take an audio line input and send it to the microprocessor s ADC. Using a fast Fourier transform algorithm, the frequency of the incoming signal will be determined and compared to the closest tonal frequency. The specific note and the magnitude of the deviation from the note will then be displayed on an LCD screen in a pattern emulating the line patterns seen on an analog strobe tuner. The main processor will be in a module containing an audio line in and line out. This box will also have one stomp switch on it to turn the tuner on and to mute/unmute the line out. There will be the option to power it by either a power source or battery. This module will connect using a 5ft cable to a satellite module containing a touch LCD screen. This second module will be able to clip onto a microphone stand to allow the user see the display easier. The user will be able to interface with the tuner through a GUI. Introduction: Analog strobe (stroboscopic) tuners have been around since They typically take a disk with lines on it and spin it mechanically at a very specific frequency. The audio input is then flashed behind the disk using a light source and any deviation from the desired pitch can be seen by the rotating motion of the lines. When the input is at the desired pitch the lines do not move, and as you move away from the pitch the lines move left or right depending on whether or not you or over or under the pitch. Strobe tuners are the most accurate tuners but they are significantly more expensive than other available tuners. This project s goal is to create an accurate digital strobe tuner that will be smaller, lighter, and cheaper than analog strobe tuners. There are already electronic strobe tuners available on the market, but ours will be unique in its size and shape. We will be using a stomp box guitar pedal interface with a satellite display of the tuning information. This will make our tuner perfect for live performance settings when tuning on stage is required. The touch screen interface will allow for the user to intuitively interact with the different functions of the tuner. Figure 1: Concept of the design 3

4 Page 4/7 Features Stroboscope Tuner Accurate real time frequency differentiation Simple and Informative Tuning interface On hidden stage presence, with foot pedal muter Satellite display allows for anywhere placement Technical Objectives Tuner Module The input signal will go through a series of low power analog filters and amplifiers in order to maximize resolution and accuracy. After the optimized input has been acquired it will be fed to the Texas Instrument (TI) DSP TMS320 ADC. The DSP, through a series of Fourier transforms, will acquire the frequency difference off of an external oscillator to ensure maximum accuracy. External memory will be used to store different tuning practices, temperature tolerance, and other miscellaneous features. Aside from an electrical input we shall also have a microphone for general tuning for acoustic instruments. The differentiation from signal periods will be transmitted to the display module while the DSP will acquire the tuning frequency from the display interface. Guitar Input Signal : 100 mv 1 V rms Audio instrumental frequency: C0: Hz C10: Hz All devices are selected for their low power consumption, for battery power, and minimal pin requirements. The circuit will be housed in a module that uses a foot pedal to allow for true signal bypass and muting. The software will be written in C to simplify Fourier transform and interfacing modules and OLED screen. Tether The tuner module will communicate with the display module through a wired or wireless communication. The Tuner module will package and transmit the necessary data through a serial peripheral interface (SPI). There will be no exchange of the original signal through the tether to ensure maximum accuracy. If done wirelessly both modules will need separate power sources, while a true wire can allow for a single power source. The single power source will most likely be housed in the LCD module as it draws the most voltage. Display Module This module houses the user interface for the device for the tuner. A series of analog push buttons will allow for the user to select tuning frequency, display option, and tuning features. The display screen will consist of a portable high resolution OLED display. A TI MSP430 or PIC microprocessor will control the display and interface with the tether to the DSP. A custom, easy to read display will allow for quick understanding and convey necessary adjustments to the instrument. 4

5 Page 5/7 Figure 2: Hardware Diagram Audio Processing Module Record A/D from Audio Signal FFT of the time domain data Software Overview Display Module Mode select through user Interface Compare freq with the desired pitch Frequency Differential Figure 3: Software Diagram Display Data on LCD screen 5

6 Page 6/7 Division of Labor: David Barnette: Audio processing software (ADC and FFT) Analog: line in, toggle switch for line out, microphone integration Design of the audio processing module Jamie Lin: LCD display layout Analog: Pre Amplifier and Signal Filter Microcontroller LCD interface Costs: TMS320C28346 Delfino Floating Point Series: $16.40 Misc. (¼ jacks, mic, transistor, op amp, resistors, capacitor, crystal, battery connector) $10 MSP430/PIC Microcontroller $2.10 Programmer $50 LCD Screen $90 Total $ Table 1: Cost Estimate 6

7 Page 7/7 Project Digital Strobe Tuner Spring 2011 Schedule David (D) & Jamie (J) Research & Design - D+J Choose/Order Parts - D+J Design Test Boards - D+J Check Hardware Functionality- D+J Software Dev - D+J Interface Modules - D+J PCB Design/Order - D+J Construct/Debug - D+J Final Presentation - D+J Figure 4: Gantt Chart 7

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