I am testing time constants for a capacitor. Practical implementation is almost accurate as theoretical calculation. But the Time const changes(rises) when I introduce an LED in series with R AND C.
cap=1000uF; Res=10K; Vcc=5V; When only Cap and resistor is present, the Time constant comes out to be 10sec at 63% of vcc which is ~3v1 and practically it comes out to be ~11sec so it's okay.
But when I introduce 2v2 Red-Led in series with it, the time const rises to 30sec. As far as I know, LED has internal resistance in mili-ohms so the R will not be the reason for this much change.Other factor is the LED capacitance, It will probably have some value but that value should reduce the Time constant instead of increasing it because it is in series with the 1000uF so the overall capacitance should be low, hence (RXC) should be low.
Am I missing something?