Today we are going to learn how to build a DIY DJ mixing board using some Pmods and a few other cost-effective materials.

Step 1: Gather Material

To start, you will need to gather materials. Depending on the intended complexity of your mixing board this can include some optional things but for the basic functionality that we are going for, you need:

A PmodSWT
A PmodBTN3
Bottle caps (I used Gatorade bottle caps)
3 small CDs
Hot Glue
Duct Tape
Breadboard and Wires
Popsicle Sticks
Tin Foi
Copper Tape
An Arduino Uno

Step 2: Building the Spinners

The most important feature on the mixing board is the ability to crossfade one track into the next.

In this design we do that by using the PmodSWT to switch on and start playing a track, then the CD spinners to control the volume and transition them into each other.

The PmodBTN allows us to attach samples or to trigger effects- right now mine is attached to two different drum beats, a police siren sound, and the classic airhorn sound.

To build the spinners take Popsicle stick and cut it in half. Then cap the ends with copper tape, or aluminum foil if you do not have copper tape. If using foil be careful- it is not as conductive as the tape so make sure to be very sparing with your usage and don't put on too much or it will not register the signal.

Then take the stick and attach wires to each side, making sure they are long enough to eventually reach back to the breadboard. I used alligator clips later to extend some wires. Then hot glue the stick tangent to the bottle cap.

Next, attach the small CD to the top of the cap. I two more Popsicle sticks, one cut into a tiny square glued to the top of the cap and one glued atop that but with the CD pinched in between. It should be glued so that it can hold down the CD but also allows it to spin.

Finally hot glue the metal binder clip so that when the CD spins it touches each contact on either side of your Popsicle stick. Attach a wire or alligator clip from the binder clip to ground.

Once you have all three spinners made, it is time to lay out the components on your board. Make sure to plan the layout before you start gluing to ensure everything fits well. Once you are satisfied with the configuration, hot glue everything in place, including the Pmods and breadboard/Arduino.

Step 3: Assembling the Board

Once you have all three spinners made, it is time to lay out the components on your board. Make sure to plan the layout before you start gluing to ensure everything fits well. Once you are satisfied with the configuration, hot glue everything in place, including the Pmods and breadboard/Arduino.

Step 4: Circuit and Code

Once the board is build its time to start on the circuit! Follow the Fritzing diagram above, and feel free to use alligator clips if wires are too short/messy.

The last step is to upload the code to the Arduino. Upload "ArduinoCodeDJ" to the Arduino board, then while still plugged into the computer run the processing sketch "ProcesssingCodeDJ" to play!

If you want to add your own tracks, simply go into the processing code line 41 and change the song titles to mp3 files of your choice. Make sure to include them in the same folder as the processing code is running out of. To attach tracks to the PmodBTN for samples and effects follow the same steps but starting on line 46.

Step 5: Start Mixing!

Now that the board is built and coded, your ready to start mixing! To use the board, make sure it is plugged into the computer running the Arduino sketch. Then open and run processing (this may take a time or two for processing to find the serial port that is Arduino is sending data through) and start messing around with the hardware. The buttons trigger samples, the switches start and stop tracks and the spinners change the volumes. Also feel free to add your own sensors and try out new ways to manipulate your music! If you are having issues, to troubleshoot a good place to start is to halt processing and open the Arduino serial monitor to make sure the sensors are sending data correctly.