Hey, I think you're right! Sucks to get old! The good news is that
I've never had to be SO precise that using RC or 1.1RC would make any
difference for me Thanks for reminding me (The bad news is that
I'm an electronics tech by day and should have remembered that! I guess
I'm waiting for the day when I get in an argument and can say I've
forgotten more than "the other person in the argument" will ever
know!!)...Cheers!!

Scott
N0EDV

K7ITM wrote:

On Nov 4, 4:02 am, Scott wrote:

Now I'm confused...doesn't Tau (Time Constant) = 1.1RC, hence 1 farad
and 1 ohm would give a time constant of 1.1? Yes, it's only 6AM, but am
I missing something?


No, the time constant of a resistance and capacitance is exactly R*C.
The time constant of a resistance and inductance is exactly L/R.

If you want to know the time at which something special happens in an
RC exponential decay, you may have to use the formula: v(t) =
v(0)*(e^(-t/RC)) (or a variation of that which accounts for the RC
changing from one voltage to a different one). So, for example, in a
555 one-shot timer circuit where the capacitor starts at (essentially)
zero volts and charges to 2/3 of the power supply voltage, we want to
find t such that e^(-t/RC) = 1/3, and that will be when t=1.0986... *
RC -- or sensibly t = 1.1*RC. And that likely is where you're
thinking of the 1.1 factor from. That's not the RC time constant;
it's the time period of a 555 one-shot timer.

Cheers,
Tom


--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)