Capacitive equations.
I seem to have great difficulty remembering these or where to find them in my university notes or even being able to find these with a net search so in desperation I have decided to put them on my own web-space.
According to my university notes the equation is as follows:
| VC | Initial (or maximum) Voltage of Capacitor |
| rV | Change in Voltage |
| C | Capacitor (in F) |
| RL | Resistive Load |
| t | Duration of discharge (s) |
VC = rV e ( -t / ( RL* C ) )
or in a more graphical format
In practice for most power supplies t is very much less than RL* C. In which case we can approximate the discharge of the capacitor to be linear and the equation simplifies to become
VC = rV ( 1 - ( t / (RL * C)))
I generally want to solve for C where we get:
C = (VC * t) / (RL * rV)
For a capacitor discharging:
| VS | Starting Voltage of Capacitor |
| VE | End Voltage of Capacitor |
| C | Capacitor (in F) |
| RL | Resistive Load |
| t | Duration of discharge (s) |
For a capacitor charging:
| VS | Starting Voltage of Capacitor |
| VE | End Voltage of Capacitor |
| C | Capacitor (in F) |
| RL | Resistive Load |
| t | Duration of discharge (s) |
