RCTIME Calculation Query

Sandgroper

Hi,

Can anybody fill me in on some details about the RCTIME calculation?·

I understand that the general formula for calculating·the time required for a fall in voltage is t = -T x (ln(V final / V initial), that T = RC, that T represents 63% of the total change in voltage, and that 5T represents 98% of the total change in voltage.· My questions are:

How do you calculate the time for a FALL in voltage if V final = zero?
How do you calculate the time for a RISE in voltage if V initial = zero?

I'm trying to calculate the time taken for an RC combination of a 220 ohm resistor and a 0.1 uf capacitor to rise· rom 0 v to 0.8 v.

Any help greatly appreciated!···

Mike Green

Do read the chapter on the RCTIME statement in the Basic Stamp Reference and Syntax Manual. There's also a nice discussion here: www.emesystems.com. Click on the "app-notes" link near the bottom of the page.

Sandgroper

Thanks·Mike, that link had just what I was looking for.· I had already read the RCTIME chapter in the manual, but it didn't have a worked example for voltages increasing from zero.·

Maybe Parallax·could include an example in the manual, e.g. 1.3 = 5*(1 - exp(-t_m/(R*C)) ?