Introduction: Student Designed RGB Bluetooth Phonograph

The goal of this project is to produce a modern take on the Edison Phonograph. This project must be under $100 and it must be able to be recreated by a high school student.


Overall, the project can be split into three areas: audio electronics, mechanical construction, and LEDs/Software Development.


Why build an RGB Phonograph?

Have you noticed that lately there is a trend to embrace vintage or nostalgic aesthetics? Everything from vinyl records to Polaroids is making a comeback, especially in art and music. A term has actually been made to describe this: Tech Nostalgia is “Using digital means to recreate aesthetics associated with analog media in an attempt to create some artistic original” [1].


This project is a simple audio solution that embraces this vintage trend. It is a modern twist of the phonograph, combining the nostalgic feel of vintage audio with modern LEDs and a modern loudspeaker to create a useable stage prop



Supplies

Supplies you may need to purchase:

  1. Individually Addressable LED Strips (5V)
  2. 5V, 8A Power Supply
  3. We recommend using a screw terminal adaptor, and the link above provides everything!
  4. If you are using a longer LED strip, be sure to look at the power rating for that strip so that you can purchase an appropriately current-rated power supply
  5. This version is 40W, which is plenty more than the 30W needed for the LED strip plus Audio Amplifier
  6. It was also recommended for LED strips
  7. Bluetooth Receiver
  8. 3" Hole Saw Drill Bit
  9. Customize to whatever size fits your speaker
  10. Class D Amplifier
  11. 4 Ohm 3W Speaker
  12. Adafruit, which manufactures the amplifier for this project, recommends this simple speaker, but feel free to spend a little more if you're an audiophile.
  13. You can also recycle a 4 Ohm speaker from older electronics if it's rated for at least 3W
  14. Two speakers can be purchased for stereo sound
  15. Wooden Box
  16. Feel free to make your own for better acoustics.
  17. Arduino Microcontroller (or similar)
  18. Cardboard
  19. 3" Diameter PVC
  20. 3.5mm jack
  21. You can buy a jack for $0.80 from a distributor like Digikey
  22. But, if you prefer something labeled and that is easy to use with jumper cables, check out Sparkfun
  23. Breadboard

Supplies and tools you may already have:

  1. Soldering iron and solder
  2. Drill
  3. Jumper cables
  4. Hot glue gun
  5. Small Philips Screwdriver
  6. Screws (optional if you'd prefer hot glue)
  7. Old Pillow for stuffing the speaker

Step 1: Providing Power to the Project

First, let's provide power to the project.


The screw terminal adapter is used to take the power from the wall to your electronics.


Cut the included micro USB cable to reveal the positive and ground wires. We are attaching them to the screw terminal so that the Bluetooth receiver can be powered all the time. In order to provide power to the breadboard, two male-to-male jumpers are used.


It's important to note that wiresshould be neatly trimmed. Exposed wiring can cause an electrical short. If you need a reference, check out the images above on what good screw terminal wiring looks like. A screw terminal is also used for the audio amplifier, so be sure that in all cases the wires are short and the screws are tightened down with a screwdriver.

Step 2: Audio Electronics

Next is the Class D Amplifier.

Adafruit has great resources about this board (including the full schematic and related projects) in case there are questions.

The headers included with the kit must be soldered on as shown in the image. Be sure to wear safety glasses when soldering and take care not to burn yourself. All of the headers are soldered with the longer side pointing upwards so that jumper cables can easily be connected. This also makes it easy to read the labels.


Next, two screw terminals are soldered on, which are for the speaker. These screw terminals are for a Left (L) and Right (R) stereo speaker system. Our project only used one speaker, so we have a yellow and blue cable going to a single speaker via the R header. The header is labeled "Rout-" and the other side of this terminal is for the Rout+. After screwing down the wires, carefully solder them to your speaker.


Now to provide an audio source!

A regular 3.5mm jack could work (those run for $1), but buying a break-out board like this makes it a bit easier to wire everything with jumpers and has labels to reduce wiring mistakes. We connected an aux cable to a Bluetooth receiver so that you can play music wirelessly via your phone. Take a look at the above wiring diagram and final project image to see how these connections are made. Each of the above images is annotated.


For a single speaker, here is how the audio jack is connected to the Amplifier:

  • Ring 1 (R+) to Amplifier R+
  • Tip (L+) connected to Amplifier L+
  • Main 5V power and GND connected to the breadboard


The R- and L- on the amplifier are grounded. This is why we made a small section of the breadboard dedicated to connecting these GNDs to the Sleeve and Ring 2 GND in one column.


Increasing the Gain

The section of doubleheaders on the bottom is for the gain of the amplifier, or how much the input is increased to give an amplified output. For our gain, we went ahead and connected a jumper from the bottom and top of the column labeled "+18" to get the maximum gain of 18 dB. This would give the loudest possible increase in volume output. If you want a quieter system, simply connect the wires across the other columns, such as 9dB. Without a jumper, the chip defaults to 6 dB. Since jumper cables are used, you can always do some trial and error and see what you like best. We recommend starting with the minimum, then powering off and adding a jumper to work your way up to whichever level you like best.


Our Bluetooth receiver arrived fully charged. Once we made sure the audio system worked, we connected the Micro USB cable that was attached to the power adapter. This makes it so you never have to recharge your receiver!

Step 3: Mechanical Construction

If a prebuilt box is used, the mechanical construction can be divided into speaker mounting and creating the horn.


First, create holes to mount the speakers and access the electronics.

Using a hole saw drill bit, make a hole where you want the speaker to go on the front side of the box. Be sure to wear safety glasses. Another hole can be made on the top of the box for the horn of the phonograph. This is where the PVC pipe will later be inserted, which supports the horn and hides the wiring from the LEDs.


Use a 17/64" drill bit to make a hole for the power supply connection on the back of the box. Another hole can be made for a button that will be for changing the RGB color pattern.


Then, hot glue or screw the speaker driver into place. The Adafruit driver is pretty lightweight, but for a heavier driver, use screws for sure. Hot glue the other electronics into place as well so they don't rattle around.


Next is the PVC for the horn.

Any size or angle of PVC piping could be used for the design of the neck. For this project there will be two pieces of 3" diameter PVC. One piece will be a longer 90 degree tube and the other one will be a shorter 45 degree tube.

Combine the two pieces of PVC using tape, glue, or a connection segment. This is where the custom angle can be created by rotating either of the pieces before combining them. Once combined the PVC should be inserted into the hole created earlier in the process. Use either tape, glue, or both to keep the PVC in place. From here the cone can be attached to the pipe.


Finally, make the cardboard horn

Make several 1/2" to 1" wide strips of cardboard, these can be of any length depending on the desired size of the cone. Apply these strips to the end of the PVC pipe at an angle to form the start of the cone and using hot glue to keep them in place.

Next, tightly roll up a 1/4" wide length of cardboard to achieve a circular shape when unrolled. The length of this piece will should be enough to wrap around the end of the cone but multiple pieces can be used if one isn't long enough to cover the end. Now that we have a band of cardboard to keep a more circular shape, use this band as a base to support more 1/2" to 1" wide strips and fill in the gaps of the cone.

Step 4: LEDs/software Development

The code written for this project is ours, and it causes the lights to change color with the amplitude of the music. However, for more resources, look at the Adafruit guide at the end.

The steps are simple:

  1. Connect the external voltage positive pin to the positive rail of the breadboard and the GND pin to the negative rail.
  2. Connect the 1000uF capacitor's positive lead to the breadboard's positive rail and the negative lead to the negative rail.
  3. Connect the NeoPixel LED strip's positive lead to the breadboard's positive rail and the negative lead to the negative rail. The strips come labeled.
  4. Connect the USB cable to the Arduino and the computer.
  5. Provide a common ground jumper wire between the microcontroller and the external power fed on the breadboard.
  6. Connect the data pin of the NeoPixel LED strip to pin 6 of the Arduino through the 200-ohm resistor.
  7. Open the Arduino IDE and create a new sketch.
  8. Copy and paste the provided code into the sketch.
  9. Make sure the board selected in the Tools menu is correct.
  10. Select the appropriate COM port under the Tools menu.
  11. Upload the sketch to the Arduino.


Now let's provide power to the Arduino.


Note: The Vin pin is not like the barrel jack on the board. There is no reverse polarity protection, only a voltage and current regulator. Take extra care when wiring your power and ground connections, as reversing them could damage your board. We recommend using a multimeter to double check your wiring is correct before powering your Arduino.

When uploading the code in the above steps, these power jumpers are not needed. Instead, use the USB to power your Arduino and upload the code through your laptop. Once you are ready to finish your project, switch over to these connections in the wiring diagram.

  • Vin receives 5V from the breadboard (which is powered via the screw-terminal adapter from step one)
  • GND receives GND from the breadboard (also via the screw-terminal)


Lastly, glue the LEDs into place around the cardboard horn. Congrats! Your project is all done!

Attachments

Step 5: Check Out These Resources

[1] J. Campopiano, “Memory, temporality, & manifestations of our tech-nostalgia,” De Gruyter, 01-Jul-2014. [Online]. Available: https://www.degruyter.com/document/doi/10.1515/pdtc-2014-0004/html. [Accessed: 23-Jan-2023].

[2] B. Earl, “Stereo 3.7W class D audio amplifier,” Adafruit Learning System. [Online]. Available: https://learn.adafruit.com/stereo-3-7w-class-d-audio-amplifier/downloads. 

[3] P. Burgess, “Adafruit Neopixel überguide,” Adafruit Learning System. [Online]. Available: https://learn.adafruit.com/adafruit-neopixel-uberguide/arduino-library-use. [Accessed: 04-Mar-2023]. 

[4] Rlah, “WS2812 RGB LED strip.” Fritzing Forum, Jan-2019. https://forum.fritzing.org/t/ws2812-rgb-led-strip-matrix/6339