This is a slightly simpler circuit than the one above. The circuit uses just one resistor and one capacitor with the 555 timer IC to create a stable and reliable oscillator with an output that it a true squarewave.
The formula for calculating the frequency is:
f=1/(1.4*R*C).
The values in the formula are expressed in ohms, farads, seconds and hertz. This formula is much simpler than that of the previous circuit. With the values shown on the circuit, the frequency is calculated as 1050Hz, but like the previous circuit, this arrangement can operate at frequencies up to around 500kHz.
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