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The oscillation frequency of this oscillator is fixed by the value of capacitor (C) and resistor (Ra) and resistor (Rb).
Roughly oscillation frequency can be calculated by the following formula.
Because there is an error of the part, the oscillation frequency of the actual circuit is sometimes different from the calculated value little.
Unit f : Hz / C : Farad / Ra and Rb : ohm
It is possible to calculate by the following formula in the time that the output becomes H level and the time which is made an L level.
It is as follows when calculating at the value of the circuit this time.
I measured the change of the oscillation frequency by the change of the line voltage.
The oscillation frequency is stable at more than +3V voltage.
It is the most stable in the voltage for 7V to 9V and it is the change of about ±1Hz(±0.1%).