[sdiy] power supply

[Scott Bernardi]

Star grounding is a good idea whenever you have sharp, pulsed currents pulling
from your supply pins (like LFOs, VCOs). Wires are just low ohm resistors, so
those current pulses will induce voltage spikes on the wires that will couple
into whatever other circuits you are powering them from.  Having all the grounds
connect to one point means the currents are in parallel paths returning the
power supply, so you don't have the series resistance problems. The exact same
reasoning is used in the separate analog and digital grounding schemes.

Tim Parkhurst wrote:

> I think "SG" is for a Star Ground. In other words, all grounds connecting to
> a single point ONLY. All the other ground connections radiate out (like the
> twinkle of a star) from this one point. I've seen this used on some boards
> with both digital and analog circuitry as part of an isolation scheme. There
> is only one point where the grounds from the digital side and the grounds
> from the analog side are tied together. What this is used for on the PAIA
> stuff, I have no idea. Am I totally off on this? Any EEs out there?
>
> Tim Parkhurst (Tim Servo)
> Design Engineer
>
> Silicon Bandwidth
> ********************************************
>
> -----Original Message-----
> From: Andre Majorel [mailto:amajorel at teaser.fr]
> Sent: Tuesday, July 30, 2002 3:16 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] power supply
>
> On 2002-07-30 16:04 -0400, Caleb Johnston wrote:
>
> > This should be an easy question to answer for the experts.  I want to
> > do this correctly so I dont fry anything.
> >
> > I have a module that runs on 1 9V battery.  I want to run this module
> > from a power supply.  The power supply is Paia's 9770u which is the
> > 'unregulated +/- 18 V DC @ 350 mA.  The connections on this power
> > supply are +V,G,SG,-V.  The module only has + and - for the battery.
> >
> > What would be the best way to do this?  Do I need to then regulate the
> > power?
>
> Yes. You could use a 7809. The selection guide says that the
> MCT7809CT can handle up to 24V at the input so it should be
> fine. Connect +V to pin 1 of the 7809 and G to pin 2. Connect +
> of your module to pin 3 of the 7809 and - to pin 2. You may have
> to tie the 7809 to a heat sink if the module sucks too much
> power (unlikely).
>
> I'm not sure what SG is. Signal ground ??
>
> --
> André Majorel <amajorel at teaser.fr>
> http://www.teaser.fr/~amajorel/
>
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--
Scott Bernardi
sbernardi at attbi.com