Help me find the filter capacitor value for my setup

[Lucifre]

I have transformer, bridge rectifier, and LM317T, I am wondering, how do i find the value of the filter capacitor to put before the voltage regulator, and it's voltage rating?

 

[MRFGUY]

Re: Cap question

Voltage rating should be higher than your max output. in your case I think 50V is fine.

For the value you can choose 470 uf.

 

[IanP]

Re: Cap question

For smoothing capacitor capacitance try to use the following formula:
Smoothing capacitor for 10% ripple, C = (5 × Io) /(Vs × f)
Io = output current from the supply
Vs = supply voltage (peak value of unsmoothed DC)
f = frequency of the AC supply (50Hz in UK)
As far as voltage, I woud say 2-2.5 x Max Dc in circuit: example - for 12V ac from transformer use 25Vdc rated capacitor..
More info here: http://www.kpsec.freeuk.com/powersup.htm
Regards,
IanP