Circuit + Stop watch + Math = Capacitance
Vin = 5
Vc(t) = 5 - 5e^(-t/RC)
Solve for C
C = t/((-ln((Vc(t) - 5)/-5))*R)
R = 1Meg
Vc(t) = Vin/2 = 2.5v (LED turns On)
Estimated time ~ 7 seconds (stop watch)
C ~ 10.1uF after calculation (1.443*7)uF
Simplified..
C = -t/ln(0.5) uF
C = t/ln(2) uF
C = t/0.693 uF
C = 1.443*(time) uF
Only useful for approximations and values greater than 1uF.
**caution** shorting large C caps might decrease the life of your button.
