microcontroller 16f707 capacitive touch button


Posted on Feb 5, 2014

there are countless applications for use of this hardware. Touch pad, proximity sensors, readout of capacitive sensors, extreme precision capacitance measurement, ultra small capacitance change detection, soil moisture, skin moisture measurement are just some of them. But then I started to search for examples and I was surprised because there wasn`


microcontroller 16f707 capacitive touch button
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t any! At least not ones that was helpfull. That is why I made this complete guide for capacitive sensing using excellent Microchip CSM module inside some of them microcontrollers. The CSM simplifies the amount of hardware and software setup needed for capacitive sensing applications. Only the sensing pads on the Printed Circuit Board (PCB) need to be added. The capacitive sensing modules allow for an interaction with an end user without a mechanical interface. The capacitive sensing oscillator consists of a constant current source and a constant current sink, to produce a triangle waveform. On picture below you can see typical waveform recorded ad one of the touch pads while measured with Microchip CSM module. To explain it simply upper current source feeds current into analog pin capacitance until voltage reaches Ref+. Then upper current source shuts down and lower current source engages. He sinks current from analog pin capacitance until voltage reaches Ref- and it all goes in circle. This is why we call it oscillator. Since it is constant current voltage is changing linearly which we can see on picture above. The oscillator is designed to drive a capacitive load (single PCB pad) and at the same time, be a clock source to one of the timers. Cap Sense Oscillator A can be input of Timer1 and TimerA depending on configuration we make. I personally prefer Timer1 since it is 16 bit timer and it is easier to count bigger...




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