Saturday, 27 January 2018

power supply - First PSU - need help with capacitor size


I am building my first power supply unit (my first project too) and need help in figuring the size of filter capacitor (and type, though I presume Electrolytic) I need to use after the rectifier diodes.


Specs:- 2 channels of 1.5VDC - 9VDC adjustable outputs with max 2.5A over both channels


Components sourced:- 229D12 Transformer - output is 12.6VCT (3.8A) at 60 Hz (65% = 2.5A) .... 4 x 1n5404 rectifier diodes (rated at 3A with Vf=1V) .... LM350 adjustable voltage regulator (rated at 3A with Vf=1.25V)


What I know so far:- 60Hz rectified is 120 cycles/sec so T=0.00833sec .... 12.6V - (2*1V diode drop) = 10.6V rectified - 1.25V (Vf of LM350) = 9.35VDC max .... Max current is going to be 2.5A (limited through LM350 and 3.74 Ohms of resistance)



I have tried sourcing the formula to calculate the size of capacitor needed, and I have seen many formulas regarding capacitors. Each one of them confused the heck outta me with funky symbols and abbreviations that I have yet to learn and each of the formulas was for something other than what I was wanting.


I speak basic English, understand average Mathematics, but still have no idea on most of the symbols and abbreviations used in EE. Please keep your answers simplified for this noob. :D


I appreciate any help ya'll can give.




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