# How do I caluclate which capacitor to use as a filter after the brdige rectifier using the 18Vpk A.C. 50 Hz as a source?

Like how would I go about on it? From calcualating the ripple voltage, to knowing which value of farads to use.

• What did your research show you and where are you stuck? There are many tutorials on the web. You need to take more care with your typing. "5OHz" is not the same as "50Hz". – Transistor Aug 7 '20 at 15:31
• Ah sorry , The O and 0 were very close to each other on my keyboard. The research shows me the the ripple factor and the calacuation to get the Vr(rms) and Vm and such – MistaEngineer Aug 7 '20 at 15:59
• So what's the question then? – Transistor Aug 7 '20 at 16:03
• Start with your specifications. (1) What voltage do you need, (2) what ripple voltage can you tolerate, (3) what is your maximum load current and (4) what is your mains frequency (which will give you the half-cycle period)? Plug those into the calculator and it will tell you the capacitance required. – Transistor Aug 7 '20 at 16:12
• "value of farads" This physical quantity is called capacitance. – winny Aug 7 '20 at 16:22

## 1 Answer

Q = C * V

which after calculus, and constant dC/dT, and a bit of algebra, becomes

I = C * dV/dT.

Making the 4 variables be "1" provides an equality.

You can substitute different values, for any 3, and compute the 4rth.