RC Time Constant Calculator
One resistor and one capacitor make a clock and a filter at the same time. This is what yours does.
Ω
µF
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The time constant
τ = R × C is the time the capacitor takes to charge to 63% of the supply through that resistor. After five of them it's within 1% of full, which is the practical definition of "charged". 10 kΩ and 100 µF give a full second: that's a power-on delay built from two parts.
The same pair as a filter
Feed a signal through the resistor with the capacitor to ground and you have a low-pass filter that starts rolling off at fc = 1 ÷ (2πRC). Everything slower passes; everything faster fades. It's how you smooth a PWM output into something resembling a steady voltage, and why the values here show both numbers: same parts, two jobs.