[SOLVED] Need explanation (Power supply 5V DC)

[Don_dody]

Power supply with CT transformer.

1. Can anybody tell me what is the function of C1, C2, C3, C4 and how we choose the right value of those capacitors?
2. Can I use only one capacitor in the left and one capacitor in the right? What will be the difference (effect) ?

Thank you.

 

[Tahmid]

1) C2 is a bulk filter capacitor. C2 should be made as large as possible. A rough estimation often used is that its capacitance should be greater than 1000uF per ampere.

C1 and C3 are decoupling/bypassing capacitors. C1 and C3 should be 100nF.

C4 is an output bulk capacitor. You can use a capacitor with capacitance between 100uF and 4700uF.

2) You should use all of them. You can omit C4, but it's better if you don't. Use a smaller capacitor if you want, even as small as 10uF to 100uF, but use it.

Hope this helps.
Tahmid.

 

[tpetar]

Switch C4 and R3, that 100nF to be on end, and 2200uF can be lower to 1000uF. 7805 can pass max 1A of current.

If you need more current 78S05 2A, 78T05 3A. In this cases bigger capacitor can be good.

Manufacturer datasheet for 7805 can be reference for design.

If you want to play more with 7805 and voltage regulators, best is to have oscilloscope and test various combinations with capacitors and rest parts.

;-)

 

[Don_dody]

Thank You very much
Everything is clear now.

 

[Syncopator]

C2 is the normal reservoir (smoothing) capacitor associated with most d.s. supplies. C4 similarly.

They are both electrolytic types, whose impedance rises with frequency - they become inductive due to their construction.

The two smaller capacitors are used to mainatain decoupling at high frequencies.

Switch C4 and R3, that 100nF to be on end,

Why?

 

[tpetar]

Why?

Provides better removal of ripple and give better result. Scope showing that.

If I find material I will post here. Its from manufacturer datasheet and from one electronic magazine where they experiment with various cap and scope.

 

[Syncopator]

Why did you say "Switch C4 and R3 (sic), that 100nF to be on end" ? I presume that you meant C3.

What did you mean?

 

[tpetar]

Why did you say "Switch C4 and R3 (sic), that 100nF to be on end" ? I presume that you meant C3.

What did you mean?

Yes I mean on C4 and C3.

 

[Tahmid]

I assume you are referring to the physical construction of the board and the components layout where the decoupling capacitor must be placed very close to the regulator. As long as the capacitors are connected close enough, C3 or C4 closer shouldn't matter.