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Date: Sun, 16 Nov 2014 13:44:56 -0500
Message-ID: <CAAhxy3DJjPS6cRA82gDua-TWghHnZreHoco-g7Zf7oONsQpAUg@mail.gmail.com>
Subject: Re: [geda-help] Multiple supply voltages
From: vattan <vatan DOT uml AT gmail DOT com>
To: geda-help AT delorie DOT com
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So far in my experience and reading (I am not a power user by a
loooong shot) hidden net/pin connections should never be used.  all
connections should be visible, all the "implied gnd and vcc'
connections are just asking for trouble, I never liked them when I
tried nad failed to use gEDA 5 years ago, and when I picked it back up
a afew months  back I thought my googling brought me to a few pages
that said the modern way of doing things is to NEVER use them.

my 2 cents.  To the rest of the devs, my offer still stands to clean
up the gSchem parts library to modern stds if someone will define them
with/for me clearly, if someone "in the know" will clean up some of
the docs.

On 11/16/14, Mike Bushroe <mbushroe AT gmail DOT com> wrote:
> Sorry, forgot to post my current config with the last post.
>
> gschem 1.8.2 (g875406c)
> gsch2pcb 1.6
> xgsch2pcb 0.1.3
> pcb version 20140316 Compiled on Aug 29 2014 at 07:56:58
> Ubuntu 14.10 (just up from 10.04 through 12.04)
> Toshiba 5.7GiB Core 2 Duo 2.2GHzx2 64bit
>
> I got an impossible to get around error when using the latest gschem,
> sch2pcb, and pcb that would load onto 10.04, and then it would delete the
> .new.pcb file with the error before I could read it and try to figure out
> what the error was and how to fix. Never did, so I was forced to finally do
> the system upgrade. I still hate Unity. But at least now the hidden error
> is gone, leaving only a few thousand obscure ones left!
>
>   I am trying to make a single phase power to 3 phase power converter for a
> friend to run a lathe, and throwing in partial speed control and reverse
> for free. As a result, I am using two full wave diode blocks to generate
> plus 120V DC and minus 120V DC for the MOSFET H-bridges to chop up back
> into 220V AC. But that means the nmos switches have to sit on the lowest
> voltage, the -120V supply rail, and the driver chip needs 15V above the
> -120V, and the digital inputs to the drivers need 5V above the -120V rail.
> That means a 7805 and a 7815 whose ground pins are not at chassis ground.
> On the other hand the ATMega that I am using to control the whole mess does
> not have the main digital power and ground pins explicitly on the symbol
> and so aren't hardwired  into the second 7805 that provides true 5V above
> ground.
>
>   I keep getting warning messages about nets being shorted together, which
> I think means that hidden attributes in the 7805 and 7815 symbol are
> shorting -120V to chassis ground. On the other hand the buried power and
> ground connections on the Atmel seem to be making Vcc pin not found errors.
>
>   I have tried copying the 7805 and 7815 symbols into my circuit directory
> and making local copies of them and removing all references to 'gnd'. But
> then I get found multiple instances errors, so I am guessing that it does
> not do 'local instance over rides global instance' type symbol loading and
> I add a dash number to the local name and re-edit the schematic to use the
> new name. I tried many ways and many power symbols to get a Vcc net going
> that the hidden pins on the ATMega would use, but that seemed to cause more
> problems than it cured.
>
>   My current guess is that I should go back to the original delivered
> symbols and find some way to override the built in hidden pin net bindings
> and either have ignore everything and just meekly go with where the wiring
> connects it or find a way to uniquely name my unusual power rails (see post
> above about trouble with names) and get them to connect to the 'ground of
> my choice' instead of the chassis ground. But I don't recall seeing any
> tutorials on how to over ride the hidden 'net:' pin attributes other than
> that I should 'promote' the hidden attribute and change it to something.
> Can anyone point me to a different tutorial that gives more specifics on
> overriding power connections? (when 'ground' really means '-120V'?)
>
> Thanks again fro your help!
>
> Mike
> --
> "Creativity is intelligence having fun." — Albert Einstein
>