RC calculation

T=RC, so:


          Time

  Resistance   Capacitance

or


      mS	  

  Kohms   uF

or


    Seconds

  ohms      F

The result gives you 1T. This is 1 time period. So for 1000uF and a 1K resistor T = 1000mS

For charging and discharging a capacitor:

1T 63%
2T 86.5%
3T 95% (this tends to be the default usage with 95% considered basically there)
4T 98% (this tends to be considered as 100% charged / discharged)
(in theory 100% is infinite)

Different voltages don't change the time to reach 1T, but will of course change the voltage measured at 1T (63% of the applied voltage).  E.g. if a 12V supply is connected via 1K to a 1000uF cap it would take 1000mS to reach 7.56V, 3000mS to reach 11.4V. Its exactly the same for discharging a capacitor.

USEFUL?
We benefit hugely from resources on the web so we decided we should try and give back some of our knowledge and resources to the community by opening up many of our company’s internal notes and libraries through mini sites like this. We hope you find the site helpful.
Please feel free to comment if you can add help to this page or point out issues and solutions you have found, but please note that we do not provide support on this site. If you need help with a problem please use one of the many online forums.