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Touch sensors
16. July 2009 - 22:04 — admin
Two touch sensors based on an ARM microcontroller.
The first one is the piece based on AT90S2313 with two sensing plates and two switches. Author (Pontus Frössander) says: "The basic idea is really simple. Make one pin output and another input. Connect a resistor between these pins. The resistor together with the human capacitance (about 100 pF) forms an RC network. The AVR set the output to low and then make a transition from 0V to +5V. 5 µs after this switch, the logic level at the input pin is sampled. If someone is touching the probe connected to the input pin, the capacitor (=human) will not be fully charged, and the input will be a digital 0 and vice versa."
Link: Touch sensor
The second one is ftom the well known ELM-CHAN pages. It implements the capacitive touch sensor (the same principle as the first one), but it provides 8 sensors and it's based on ATTiny2313.
Link: Simple touch sensor