# Calculating resonant frequency in series RC oscillator

by opticaltempest
Tags: frequency, oscillator, resonant, series
 P: 135 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/en..._02chapter.htm 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.
 P: 2,432 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. . 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.
 P: 2 I'm no expert but it sounds like the 555 timer chip. This chip uses capacitors and resistors as a reference time constant, then from this creates a pulse signal. By the way the output of the 555 timer is not strictly A/C sinsoidal but sawtooth.So almost like using a rapid on/off switch with C & R setting the speed.

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