# Calculating resonant frequency in series RC oscillator

1. Jan 6, 2006

### opticaltempest

What is the formula to calculate the oscillating (resonant?) frequency of a series RC circuit with a constant DC voltage?

For example the RC circuit shown at this site:

http://www.mikroelektronika.co.yu/english/product/books/PICbook/2_02chapter.htm" [Broken]

How does this circuit resonate with a DC voltage? Aren't capacitors supposed to act like an open circuit to DC voltage?

I have searched all over using google but cannot find details on RC oscillators.

Last edited by a moderator: May 2, 2017
2. Jan 6, 2006

### Averagesupernova

There is more going on inside the microcontroller than you are able to see. The RC circuit sets up a time constant. When the voltage is first applied to the circuit there is a specific amount of time it takes before the voltage at the node of the capacitor and resistor reaches a specific level.
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Think of it this way: The microcontroller senses this voltage and modifies the circuit to discharge the capacitor at a specific rate. Then it senses a lower limit and allows the capacitor to charge again.

3. Feb 1, 2006