Today we will show you an interesting way to create a touch surface using only the TiTAN board without any specialized chips.
Look what we’ve got.
How does it work?
You know that the human body is capable of accumulating an electric charge. This feature will be used by us. A little theory.
Let’s consider such a scheme in which the capacitor has one of the plates capable of “changing its size” when we touch it and a button that helps to discharge the capacitor plates.
After releasing the button, the capacitor starts charging to the battery voltage through the resistor and it takes some time. This time depends on the values of the capacitor and the resistor and will be almost always the same.
But if we touch the lining of a capacitor, its electrical capacity and the electrical capacity of our body will change.
If we press and release the button, the charging time of the capacitor will change. It will be more or less from the previous one, depending on the electrical interference gathering on our body.
The graph of the change in the charge time of the capacitor will look like this.
The blue color indicates the charge time of the capacitor to the logical “1” level without touching, and red and green with touching. This is the time change we will monitor.
Let’s assemble the circuit of our sensing device and connect it to the TiTAN board.
Pay attention to the design of the touch sensor. It contains additional layers of dielectric to protect the microcontroller from static voltage from our body, which can disable it. And an additional layer of copper will ensure a uniform transfer of the electrical capacity of our body to the capacitor lining.
Here is an example of a touch sensor design.
As a voltage source for charging the capacitor, we will use ports P2.0 and P2.2
You can download the firmware source code from our website.
In it, we determine the touch to the sensor and transmit this information by radio.
The second TiTAN board displays this information in the switch mode on the LED.
Using this example, you can apply touch control in your ideas.