Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 14 | The Remote Wah Guitar Pedal |
Christopher Read Julian Brookfield Luna Rathod |
Stasiu Chyczewski | design_document1.pdf final_paper1.pdf final_paper2.pdf photo1.jpg proposal1.pdf proposal2.pdf |
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| # Title The Remote Wah: Remote Activated Guitar Effect Team Members: Julian Brookfield (jbrook32) Chris Read (clread2) Luna Rathod (drathod2) # Problem Guitar and bass players have a wealth of effects pedals to choose from in order to modify the sound of their instrument, such as adding distortion, echo, reverb, etc. In most cases, the parameters for effects pedals are set by the player beforehand and turned on and off with a footswitch, or controlled by a foot treadle to modify a single parameter, such as the sweep of a high-Q bandpass filter in a wah pedal. However, this requires the player to remain fixed in place while using the effect, which can get in the way of the performance aspect of playing live music. It would be very helpful & expressive to have a way of controlling the parameters of certain effects while maintaining the ability to move around a stage unimpeded. # Solution Our idea is that rather than using a foot treadle to control the filter sweep of a wah pedal (see [here](https://www.youtube.com/watch?v=2lbENbvVIg0) for reference), the range of the filter sweep is controlled by a sensor mounted to the headstock of a guitar/bass. This allows achieving the characteristic sweep sound of a wah by swinging your guitar up and down rather than using a foot treadle, which allows the use of the effect anywhere on stage (after you switch it on) and makes for an interesting visual accompaniment that is suited for live performance (it would look pretty cool). To further aid in freedom of movement, the effect will have the ability to be remotely activated via a button mounted to the body of the guitar within convenient reach of the player. # Solution Components ## Subsystem 1: Headstock Transmitter This will be a small device mounted to the headstock of the guitar. It will include some sort of [IMU](https://www.digikey.com/en/products/detail/stmicroelectronics/LSM6DSMTR/6192777) to gather data about the motion of the guitar’s headstock as it moves up and down. This data is then transmitted wirelessly to the receiver pedal through a prefabricated RF module such as [this](https://www.signetik.com/product/M1-N1). The transmitter will run off of commonly available button-cell batteries and include a simple power indicator LED and an on/off switch that is activated before/after a performance, respectively. It should be housed in a small non-metal (probably 3D-printed) enclosure to allow transmission of RF signals, and should be attached to the headstock via an elastic strap. For simplicity, the transmitter will continuously send data to the receiver while it is on, however this can later be changed to sleep while the effect is off and transmit data only when the effect is on in order to save battery life. ## Subsystem 2: The Activator Button(s) This will be a small button that is placed in a convenient location on the body of the guitar. This button sends a wireless signal to the receiver pedal to turn the effect on and off, also through the aid of a prefabricated RF module. It will similarly be powered by a coin cell battery, include a power LED and on/off switch that is used the same way as the transmitter, and be housed in a small 3d-printed enclosure. However this device will be mounted to the guitar body via some sort of stick-on adhesive, and eventually could be attached via custom plates which can attach to screws on the pickguards found on most guitars. While we only need a single button to engage the single wah effect contained in the receiver to start with, this can be expanded to contain multiple buttons that can control multiple effects built into the receiver (such as adding a distortion circuit) and even external pedals via extra I/O jacks. ## Subsystem 3: The Pedal Receiver This will be the main heart of the project and is functionally divided into an analog half and a digital half. The analog half will include the wah effect & bypass circuit that the guitar is routed through. A large part of the classic sound of wah effects has to do with the particulars of which inductor is used to create the peaking filter, so this part is best left analog. It also avoids any latency in the guitar signal since the audio path remains completely analog. The digital half will receive and process the button and IMU data into useful control signals that control the analog half. This includes processing the raw IMU data into a useful range that controls a digital potentiometer, which in turn controls the sweep of the analog filter in the wah effect side. This sweep must be calibrated by a footswitch, which is configured before the performance to allow for any range of motion of the guitar to generate a useful sweep of the wah. The range of the sweep will be formatted to control a [digital potentiometer](https://www.mouser.com/ProductDetail/Microchip-Technology/MCP4018T-103E-LT?qs=%2FsslhGPpiOSWJSDZcNYXEg%3D%3D), which will interface to the MCU with I2C, thus the MCU has to process the IMU data into a range that controls the digital potentiometer across its full sweep. The button data will also be processed into a control voltage that switches signal relays/analog muxes to either activate or bypass the wah effect. All this will require two complementary receiver RF modules (or a single module with multiple antennas) in order to receive data, and will primarily run off of an STM MCU, such as the [STM32F3](https://www.digikey.com/en/products/detail/stmicroelectronics/STM32F3DISCOVERY/3522185). There are many [standard prefabricated pedal enclosures](https://lovemyswitches.com/enclosures/) available that allow for easy housing. Additionally, this pedal can run off of a [9V DC power supply](https://truetone.com/1-spot/) that is standard for effects pedals, meaning power consumption isn’t an issue. If time allows, this receiver system can be expanded to include signal routing for more built-in effects and external effects pedals via extra buttons on the activator device as mentioned previously. In the end, this project could form the basis of a whole line of products, including wirelessly controlled single-effect pedals and wireless pedalboard controllers which are guitar-mounted. # Criterion For Success The receiver is able to process the raw transmitter IMU data into a usable digital potentiometer sweep. The activator button is able to turn the effect on and off. Successful interfacing between receiver microcontroller data and circuit hardware (switching effect on and off, controlling sweep of a pot).  [Visual Aid](https://drive.google.com/file/d/1v3A_eR558loARLxpFDfFlpcltEsvwx2l/view?usp=sharing) |
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