[sdiy] 5V power supply for logic and uC

[ChristianH]

On Fri, 2 Nov 2012 09:01:18 +0100 Mattias Rickardsson <mr at analogue.org> wrote:

> It feels like it might be a good idea to use the -12 V rail instead,
> with some inverting switching regulator - both to minimize the lost
> power and to avoid drawing current from the +12 V rail, which is more
> likely to be heavier loaded than the -12 V already. 

Howzat? Do you have lots of hard disk drives in your synth sucking from
the +12V?
Usually, bipolar power supplies are used for opamps etc., I wouldn't
expect significant asymmetric loading here.

However, having an avoidable switched DC-DC converter screaming in a
synth circuit makes me shudder.

I do see the point of using +12V for local references, but if you start
calling something a reference voltage you better not use raw +12V for it
anyway. It wouldn't matter if it gets some spikes from a microcontroller
or from some VCO reset surges.
If I need a reference, I usually pop in a cheap LM336, or if I'm feeling
generous an LT something. And add some filtering to it.

Call me old fashioned, but in the case mentioned I'd add a +5V PSU.

Chris



> On 1 November 2012 18:40, Thomas Strathmann <thomas at pdp7.org> wrote:
> > Hi all,
> >
> > I'm planning a number of modules that will need a 5V supply to power
> > logic ICs and microcontrollers from the 12V rail of a Doepfer modular.
> > What I'd like to know is what measures I should take to protect the rest
> > of the modular from noise. What I'd do at this stage is just add a 7805
> > voltage regulator with the standard caps from input and output to GND.
> > Is this a recommended approach or is there a problem with this?
> >
> >         Thomas