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How many capacity does it need everywhere ?
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Jan Audio:
Hi, i have this project, it runs on a 15volt wall-adapter, and takes 100mA.
The 15 volt can be from switching or linear power-supply.

The 15 volt goes into a 12volt regulator, so it dont matters what adapter is used to keep all in tune.
The 12 volt goes into 2 5volt regulators, one for digital one for analog.
The 12 volt also goes into a 6volt regulator.

The 12 volt goes into more then 10 circuits each having theyr own 10u or 22u capacity on board.
Same for the 5 and 6volt all having 10u on almost all circuits, exept where no space only has 100n each IC.

Every regulator has 100n and 330n ceramic where needed on in and outputs.

So how many capacity do i need where ?
Where the 15volt power goes in i need a big one ?
How about directly on the regulator outputs ?

thanks in advance.
AVGresponding:
Sounds like you have enough already.

The overall current your project uses is small, a 100n cap by each digital IC is good, 10u on each in and out on the regulators would be fine.
As for the analog, you might need a selection of small caps, it depends what kind of frequencies you are expecting to see. If it's in the audio range, you might use, say, a 1u + 100n in parallel.

If you have a 10-22u reservoir cap on each circuit, I see no reason to add another larger one on the 15V stage, those linear regulators are pretty good at supply noise rejection, but if you're really intent on belt and braces, add a 100-220u cap there too.

Remember to post pics of your finished project!   ;D
floobydust:
The input capacitor (to 12V reg) is important, usually 10-1,000uF depending if the 15V wall adapter an SMPS or 50/60Hz transformer, to deal with the ripple that is there. 100mA is a small load. If you have a 15V SMPS wall-adapter running at 66kHz, then a linear voltage reg usually does not cope with the harmonics, LDO ICs are slow.

Huge capacitors are used for lowest ripple and noise, even >1,000uF on linear regulator outputs for audio DACs and pre-amps. It's a bit crazy in some designs.
A danger is during power-down or power-up, that one rail goes up/collapses first but the other is behind/stays up. It can cause IC's to latch up, so you need extra protection diodes.

It's better to smartly use LC filters, ferrite beads to control HF noise from a SMPS wall-adapter, instead of using huge capacitors or having a million small ones everywhere.

I would put an LC filter at the 12V reg's input, a few uH and 100-470uF and the other capacitors seem OK.
Check with a scope the 5V digital noise is not polluting the 12V rail, you might use a ferrite bead there. I don't know what all this is powering.
Jan Audio:

--- Quote from: floobydust on November 12, 2019, 05:00:39 pm ---The input capacitor (to 12V reg) is important, usually 10-1,000uF depending if the 15V wall adapter an SMPS or 50/60Hz transformer, to deal with the ripple that is there. 100mA is a small load. If you have a 15V SMPS wall-adapter running at 66kHz, then a linear voltage reg usually does not cope with the harmonics, LDO ICs are slow.

--- End quote ---

Yes i have a linear 7812, and possible a switching wall adapter.
So the big cap is needed for sure ?, all good now ?, ok.
Adding 1500u from 15 to 12v regulator.


--- Quote from: floobydust on November 12, 2019, 05:00:39 pm ---Huge capacitors are used for lowest ripple and noise, even >1,000uF on linear regulator outputs for audio DACs and pre-amps. It's a bit crazy in some designs.
A danger is during power-down or power-up, that one rail goes up/collapses first but the other is behind/stays up. It can cause IC's to latch up, so you need extra protection diodes.

--- End quote ---

I dont have dual rail, just a 6v virtual ground.
All opamps have cap between negative input and output.


--- Quote from: floobydust on November 12, 2019, 05:00:39 pm ---It's better to smartly use LC filters, ferrite beads to control HF noise from a SMPS wall-adapter, instead of using huge capacitors or having a million small ones everywhere.

I would put an LC filter at the 12V reg's input, a few uH and 100-470uF and the other capacitors seem OK.
Check with a scope the 5V digital noise is not polluting the 12V rail, you might use a ferrite bead there. I don't know what all this is powering.

--- End quote ---

I dont have uH coils in house, i dont use them normally.
Do i need it ?

For the 5V noise, should i take it from the 15 volt maybe ?, or is it bad for a linear regulator to take away at least 10volt ? ( non switching unstabilized can even be 18 volt or more )
Can use heatsink.

I do have a switching 5v regulator, if it is better for the MCUs and diplay.
I dont know about ferrite beds at all.
Jan Audio:

--- Quote from: ThickPhilM on November 12, 2019, 04:40:24 pm ---Remember to post pics of your finished project!   ;D[/color][/b]

--- End quote ---

I am ashamed in how much work i put in a simple sound, totally in DIP with wires and all.
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