Have you ever wanted to make a giant trackpad? With this tutorial you can make any size of trackpad/force-pad and test it with the included software demo.
We are ONIRIA, we create content, design hardware and develop software to erase the limits of reality and immersive technology.
In the search of full immersion for the virtual experiences we create, O-mat was born. O-mat is an interactive mat that recognizes steps. It is built with 225 (a 15 by 15 matrix array) pressure sensors made of a special material called velostat. This material changes its resistance when pressure is applied to it. We designed an Arduino shield so it could be easy to use, scalable and open platform (coming soon).
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Step 1: The Materials and Tools
For making the mat:
- Measuring tape
- Soldering Iron
For making the circuit:
- 2 Multiplexers
- 1 breadboard
- 1 arduino, for this case we use a mini pro
- 2 leds
- 16 1k [ohm] ressitors
- 2 220 [ohm] resistors
- Wire strippers
- Diagonal cutters
Step 2: For the Mat - Part 1
Use this Youtube video as a guide.
The key component that makes O-mat work is the velostat. When pressure is applied to it, the velostat changes its resistance. Like you saw in the video, we are creating a matrix sensor, specifically a 15 by 15 sensor matrix (225 sensors!).
Step 3: For the Mat - Part 2
Summing up, you will end having two sides of the mat, one with copper columns and one with copper rows. You will need to weld one by one (I recommend using a ribbon cable for ease of use). You will need to insert the velostat between the to sides of the mat. To finish, you will need to paste both sides of the mat and you are ready to start the circuit.
If you want to make a quick test, with te help of a multimeter, sense one of the pins of the ribbon cable connected to the copper rows of the mat with one of the pins of the ribbon cable connected to the copper columns of the mat. Apply some weight to the mat and see if the resistance changes, if you don´t see that the resistance changes apply weight in other area. If still you don´t detect a change in the resistance check that you make a good welding in the copper areas and the velostat is between.
Step 4: For the Circuit
Use as guidance the circuit diagrams that are above.
When you finish connecting all the parts in your breadboard, connect the two cables of the mat, it doesn't matter the orientation or the order.
We have just designed the arduino shield, If you want one, you can contact us in our web page!
Step 5: Connect It to the Computer
Step 6: The Code - Arduino Sketch
Before you upload the arduino sketch to the micro-controller, check that the pins are connected as the first lines of the code.
Below is the configuration for the arduino mini pro as the circuit diagram that is in the previous step, this configuration is the default configuration in the arduino sketch
//Mux control pins for analog signal (SIG_pin) default for arduino mini pro const byte s0 = 13; const byte s1 = 12; const byte s2 = 11; const byte s3 = 10; //Mux control pins for Output signal (OUT_pin) default for arduino mini pro const byte w0 = 9; const byte w1 = 8; const byte w2 = 7; const byte w3 = 6; //Mux in "SIG" pin default for arduino mini pro const byte SIG_pin = 0; //Mux out "SIG" pin default for arduino mini pro const byte OUT_pin = 5; //Status and Column pins default for arduino mini pro const byte STATUS_pin = 3; const byte COL_pin = 2;
If you decided to make the circuit with an arduino uno, the configuration of the pins must be like the code bellow
//Mux control pins for analog signal (SIG_pin) default for arduino mini pro const byte s0 = A4; const byte s1 = A3; const byte s2 = A2; const byte s3 = A1; //Mux control pins for Output signal (OUT_pin) default for arduino mini pro const byte w0 = 6; const byte w1 = 5; const byte w2 = 4; const byte w3 = 3; //Mux in "SIG" pin default for arduino mini pro const byte SIG_pin = 0; //Mux out "SIG" pin default for arduino mini pro const byte OUT_pin = 2; //Status and Column pins default for arduino mini pro const byte STATUS_pin = 8; const byte COL_pin = 9;
Step 7: The Code - Processing
For the processing code, you will have to change only one number. You will have to change the number inside of the Serial.list()[numbertochange]. Without changing anything in the processing code, try to run the code, in the console window you will see the list of the serial ports, identify the arduino serial port and use that number for modifying in the following line:
myPort = new Serial(this, Serial.list(), 115200);
In mi case i found that I have it to change it to
myPort = new Serial(this, Serial.list(), 115200);
Step 8: Play With It!
If you starting to see that the one of the leds starts blinking and you saw a screen like the one above, you have made it. You can start playing with your new O-mat!
1 Person Made This Project!
SuriS4 made it!