In this we are going to explain are to how to create a small midi controler from molded rubber, and a pressure sensor. This pad is designed to be used as a creative/rhythmic aid for musicians composers and buskers.
The finished piece can be attached to the bottom of a shoe, or placed under the insole and is activated by pressing ondown the rubber pad.
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Step 1: Making the Mold
The first step for this project is to make a mold to cast the rubber pad. The mold is made from 1/2" MDF. MDF is dimensionally stable, readily available, and easy to use with power tools.
For this step you will need
- a plunge router with a 1/2 bullnose bit, and a collet that acts as a guide.
- a 1/4" round file
- a 1 3/4" forstner drill bit and drill press
- 1/8" drill bit
- 1/8" dowel
- a can of spray paint
Use the forstner bit and the drill press to drill a hole through a piece of MDF. The piece of MDF can be any size but a scrap piece that is roughly 8" x 8" will suffice. *Remember to use saftey glasses and exercise extreme caution and best saftey practices with all power tools.
You will now have a 1 3/4" hole in a piece of mdf. Use two side tape to attatch that mdf tothe top of a another piece of 1/2" mdf that is roughly the same size.
Now you can use the plunge router (set up with the 1/2" bullnose and collet) to create the shape of your mold.
The router collect will run on the inside edge of the 1 3/4" hole in the top piece of MDF. The size of the collet will effect the diameter of your final mold. The final size will ideally have a diameter 1 3/8" (+- 1/4").
You can also control the depth of the mold by adjusting the depth your routers plunge. The final depth should be 3/16" (+- 1/16th).
Use the 1/4" file to make a rough slot coming off the side of the mold (this will be useful when placing the pressure senseor in the mold).
In the center of the mold drill a 1/8th inch hole. Glue a piece of 1/8th inch dowel into the hole. It should be glued in so the top is half the depth of the mold.
Use the spray paint to paint the mold. 2 coats is recomended. Sanding between coats will result in a smoother mold.
You now have a mold. Celebrate responsibly.
Step 2: Pouring Your Rubber Pad.
For this step you will need
-4 ounces of PMC 121-30. This is a two part product rubber product so you will only need 2 ounces of each part.
-Mold release. You can use petrolium jelly, or mold release spray
-a hot glue gun.
-a pressure sensor
- 2 pieces of 4' long of light gauge electrical cable.
- 2 2" pieces of heat shrink cable that corrispond to your electrical cable.
- Masking Tape
Solder the wire to the leads on your pressure sensor. Now seal the joints with the heatshrink tubbing. The ideal pressure sensor will be 3/8" in diameter.
Cut a very small piece of masking tape to place on top of the dowel in your mold. This will protect the dowel tip when coating your mold with mold release. *You only want to mask the very top of the dowel, the sides should be left uncovered. In a well ventilated area lightly coat your mold with two light coats of mold release. This is very important because the PMC 121-30 has great adhesive qualities, and will prove to be impossibe to remove form the mold otherwise.
Now carefully remove the masking tape from the dowel. Be careful not to contaminate the dowel by touching the sides of the mold that have mold release.
Place a very small dab of hot glue on top of the dowel and than place your pressure sensors into the glue.
Now mix up the PMC 121-30. The PMC 121-30 is a two part rubber mixture. The ratio of the mix is 1 to 1 so it is important to measure the volumes very carefully. Try to be accurate to the milliter if possible. Mix the two parts together for roughly 2 minutes. You can also add colourants to the mix if you want. We used white and black to make grey. Roughly 2 drops of each. It is important to make sure the colourants are compatable with PMC 121-30.
The final step is to pour the mixture into your mold. Let the product cure over night.
You should now have a rubber pad with pressure sensor inside of it.
Step 3: Electronics
For making the sound and
pressure sensor work you need to have these:
Arduino app (https://www.arduino.cc/en/Main/Software)
Processing app (https://processing.org/download/)
Here we go:
Open your arduino app, copy and paste the code that’s provided, connect the arduino to your system, then upload the program into it.
Then you need to open your processing app and copy the code for processing into it. Save the program under the name that you want. Then go the same folder in your system, and follow this order:
(Processing-->choose the folder-->open data ) here you will see sounds, now you can easily drag and drop any sound that you need.
*remember to name them as 1.wav/2.wav/3.wav and go on.
At this part you have to programs working together.
Next step is to build the circuit for the arduino and your pressure sensor. Follow the picture.
then connect one side of your sensor to + and the other side of it to A1. for other sensor the same expect one side of has to be connected to A0.
you either need to connect the arduino to your system or battery for power.
now your midi dot should work.