Calculate the RC time constant and the charge or discharge curve it produces.
The capacitor charges exponentially, reaching 63.2 per cent of supply in one time constant and about 99 per cent in five. The corner frequency of the equivalent filter is the reciprocal of 2πτ. Five time constants is the standard settling allowance in timing and sampling circuits, because the remaining error is below one per cent.
RC Time Constant
τ = R C; V(t) = V_supply (1 − e^(−t/τ))
τ = R C; V(t) = V_supply (1 − e^(−t/τ)) The capacitor charges exponentially, reaching 63.2 per cent of supply in one time constant and about 99 per cent in five. The corner frequency of the equivalent filter is the reciprocal of 2πτ.
Five time constants is the standard settling allowance in timing and sampling circuits, because the remaining error is below one per cent.
This calculator takes 4 inputs: Resistance, Capacitance, Supply voltage, Time elapsed. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.