W.A.R.P – Wirelessly Accessible Record Player
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and using the physical buttons on the record player. W.A.R.P – Wirelessly Additionally, the mobile application can be used to control the record player’s power, rotation speed, and what Accessible Record Player specific song on the record is being played. Whenever a new song is selected, the record player arm will be lifted Martin Do, Jose Medina, Micaiah Reid, and off of the record, moved to the appropriate location over Daniel Weinberg the record, and then gently lowered onto the record to continue playing music. This will allow the user to have Dept. of Electrical and Computer Engineering nearly full control over the record player remotely. Some University of Central Florida, Orlando, Florida, new controls were also added to the record player 32816-2450 including a ‘go home’ function that lifts the tonearm off of the record and moves it to the tonearm’s stand and a ‘anti- skip’ function that lifts the tonearm and moves it over one Abstract — The objective of this project was to create a grove to avoid skipping. working vinyl record player in which all manual controls of the record player can be optionally controlled remotely through a mobile application. The mobile application that II. SYSTEM COMPONENTS accompanies the record player is also a platform with which A. A. Record Player to catalog a user’s record collection, and Optical Character Recognition algorithms will be implemented in order to help B. As a record player is not being made from scratch but the user to quickly search for records to catalog. The user rather modified to meet the specifications desired in can take a picture of the record label and it will be searched creating WARP, record player selection was an important for automatically. component of designing WARP. An ideal record player Index Terms — Audio systems, bluetooth, character would be easily modifiable (though this is a difficult recognition, stepper motors, home automation. specification to measure) and have a sturdy, heavy turntable. Since many modifications were to be made to I. INTRODUCTION the record player, the heavy turntable was key in maintaining high sound fidelity. For this project, the Vinyl records, once a nearly obsolete product, have Stanton T.62 was chosen, as it offered great sound quality been rising in popularity. Though vinyl records and record and a heavy turntable for a reasonable price. players have many drawbacks when compared to modern C. digital music consumption methods, including D. B. Microcontroller inconvenience of use, difficulty of distribution, and increased production and manufacturing time, there are E. The microcontroller will be used to connect the record also many advantages to the record players. One major player to the user’s mobile device. Commands are sent advantage of the record player is that the record player’s through bluetooth from the user’s device to the system for generating sound is completely analog; the microcontroller. The commands available are to start and sound is never sampled and digitized, giving it a sound stop the record player’s rotation, to change the rotation quality that is truer to the original recordings. The main speed to either 33 ⅓ RPMs or 45 RPMs, to change songs, goal of WARP is to remove as much of the first to move the tonearm “home”, or the “anti-skip” command, disadvantage – inconvenience of use – as possible in which lifts the arm up and lowers it back down to help using a record player. avoid skipping on the record. For WARP, the Nordic The main inconveniences in using a record player are NRF52832 was used. tedious setup, difficulty in song selection, and the need to F. physically go to the record player to change songs, flip the G. C. Tonearm Controls record, lower the volume, or turn off the record player. Though the tediousness of setup are not addressed by H. Controlling the movement of the tonearm is a key WARP (as in, the user will still need to place the record on component to WARP. The two main specifications the platter, etc.), the difficulty in playing songs and the regarding the movement of the tonearm are to place the need to be at the record player to control it are solved with needle within 5 seconds of the designated track on the WARP. album, and to do this placement in less than 5 seconds. To WARP consists of two main systems: the record player meet the first specification, the accuracy of the tonearm and the mobile application that controls the record player. placement must be extremely constant and accurate. More The record player maintains the ability for the user to use details on how these were accomplished will be discussed all manual device controls, such as moving the tonearm, in Section III. III. HARDWARE DESIGN having a charging an electromagnetic coil to hold a separate disk to the inner axle of the clutch. The disk is A. Motors/Drivers attached to the tonearm, thus allowing separate motion When designing WARP, one of the most important from the motor when necessary. aspects is the horizontal movement of the tonearm. There The clutch requires a constant 12 volts in order to be were several suggested implementations for project engaged. When 12 volts is not supplied, the clutch is functionality, such as using a DC motor with linear disengaged. Engaging and disengaging the clutch is encoder or implementing a position feedback servo motor. controlled by connecting a GPIO pin of the MCU to the Ultimately, a stepper motor with a planetary gearbox was gate of a mosfet which connects the ground to the clutch. chosen due to its precision and reliability. Due to the This allows for control of the clutch via the MCU. extremely small spacing between grooves on a vinyl record, a stepper motor with an extremely small step angle C. Sensor was needed to meet the specifications for the project. In While not completely necessary for full functionality of addition to the precision requirements, the motor must also the project, introducing a sensor helps lower the overall have enough torque (after step angle reduction) to move latency between song changes. When calibrating the the tonearm smoothly. A standard NEMA 17 stepper tonearm back to the default location between each song motor with a planetary gearbox in addition to change, the number of steps required is unknown. Without microstepping from a stepper motor driver reduced the some way to detect that the tonearm is at the default step angle enough to meet the requirements. location, the horizontal motor will keep stepping but not The motor used for the vertical movement does not step past the stopper at the default location. This is the need to be as precise as the horizontal motor. Consistently implementation used in 3D printers. This implementation moving from one set position to another would meet the is suboptimal due to the small step angle. Depending on requirements for this motor. For this, a standard NEMA 17 the angle of the tonearm before movement, the motor can motor was used. The main reason for this choice was so perform several thousand unnecessary step, potentially that drivers and mounts used for the horizontal movement introducing several seconds of latency. To meet the can be repurposed and used for the vertical movement. specifications of a maximum latency of 5 seconds between The A4988 was the driver chosen for this project, song changes, this can potentially become unacceptable. primarily due to the 16th step microstepping functionality. Texas Instruments' LDC0851 differential compensated This 16th step microstepping divides the step angle of the and highly accurate inductive switch was chosen to detect motor by 16, helping meet the accuracy specification of when the tonearm reaches the default location. The the project.. According to the A4988 datasheet, the clock LDC0851 works by giving a low voltage whenever a period required for each step is 2 microseconds.. This conductive material cover the attached inductive coils. corresponds to a frequency of 500KHz. However after The output of the LDC0851 will be attached to a GPIO pin testing, using that high of a frequency, in addition to and perform an interrupt on the negative edge of the microstepping and the gearbox, reduces the torque to an sensor's output signal. The inductive coil is attached to the unusable level. It was decided to lower the frequency to tonearm's resting position (which is the tonearm's "default 3KHz, which is more than sufficient to meet the required location"). Attached to the tonearm is copper foil which latency specification. reliably triggers the sensor. To ensure the the tonearm constantly stops at the same location after triggering the B. Clutch sensor, the horizontal motor controlling the tonearm Attaching the horizontal motor directly to the tonearm continues to step several times. leads to several complications for the project. For example, the user will be unable to move the tonearm D. Button Controls manually due to the holding torque of the stepper motor The Stanton T.62 record player that was selected had combined with the gearbox. This alone is a significant three circuit components that needed modification – the issue which conflicts with the specification stating that the rotation start/stop control button and the two speed control user should be allowed to still manually operate the record buttons. In order to allow for the microcontroller to player. This is not the only issue involve. While playing control these circuits while leaving the actual buttons the record, holding the tonearm firm will cause the record intact and functional, the record player was disassembled to skip as well as potentially damaging the vinyl.