[sdiy] Power distribution board

[Laurie Biddulph]

Hi,

Some systems, like Eurorack, offer the option of a 3rd power rail which is 
assigned to 5V. This solution minimises heat dissipation through high 
voltage drops to the 5V rail but does increase the potential (pun!) for 
voltage drops which are far more critical on 5V circuits. Given the number 
of modules that actually need a 5V supply I would say that it makes far more 
sense to do the regulation on board, when and where it is needed. This will 
increase the loading on the (usually) positive rail but this is a small 
price to pay.

I would definitely NOT use divider resistors. Any variation in the main 
power rail will show itself in this divided output. For the sake of a few 
cents you should definitely use a regulator. Heat dissipation shouldn't be a 
problem but if you are really drawing that much power then it would be worth 
considering running a separate bus cable.

Best Regards

(Mr) Laurie Biddulph
Phone: +61 (0)2 4340 0938
Mobile: 0400 257 645

Elby Designs
ABN: 70 022 727 605
http://www.elby-designs.com

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----- Original Message ----- 
From: "David G. Dixon" <dixon at interchange.ubc.ca>
To: "'Roy J. Tellason'" <rtellason at verizon.net>; 
<synth-diy at dropmix.xs4all.nl>
Sent: Sunday, April 05, 2009 3:30 AM
Subject: RE: [sdiy] Power distribution board


> This leads to my next question:  Presuming that most have only +/-15V
> supplies in their modulars, what is the best way to handle digital power?
> I've only breadboarded circuits with TTL chips powered by a 7805 reducing
> +15V to +5, and was startled (and a little frightened) at how hot the
> regulator ran.  I'm not sure I'd want anything that hot on any of my
> lovingly hand-crafted boards!
>
> I was thinking I would probably opt for just putting the +15V through a
> simple voltage divider to get +5V and be done with it, but I'm wondering: 
> is
> this anathema?  Does one find oneself excommunicated from the fold for 
> such
> heresy?
>
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
>> bounces at dropmix.xs4all.nl] On Behalf Of Roy J. Tellason
>> Sent: Saturday, April 04, 2009 10:14 AM
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: Re: [sdiy] Power distribution board
>>
>> On Saturday 04 April 2009 05:50:29 am Julian wrote:
>> > Somthing ive wondered -
>> >
>> > Regulators are cheap - what about a power bus running over-voltage and
>> then
>> > a pair of dedicated regulators for each and every socket on that bus?
>> >
>> > Would that effectivly isolate every module?
>> >
>> > (im thinking back to my old doepfer lfos thatlld modulate the doepfer
>> vcos
>> > on the same bus...)
>>
>> That was the approach taken for the real early S-100 bus computer 
>> systems,
>> with the power buses being 8V, and +/-16V,  which were typically 
>> regulated
>> down to 5V and 12V on each board.  Some boards had to have multiple
>> regulators for the 5V,  and there were heat dissipation issues.  Later
>> systems put jumpers in place of the regulators and used switching power
>> supplies instead,  though I've not much experience with them.
>>
>> But yeah,  I'd say this would provide a lot of isolation.
>
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