Difficulty with "power" and "supply"

Am 26.04.2011 11:13, schrieb Richard Bennett:

Hey guys, just just hit the floor with this stuff, so bear with me... I

just created my first device, and it seems to work ok.  The only concept

that's still giving me fits is the PWR and SUP pins. I'm not sure what the

difference is and/or where one is used instead of the other. Also, the use

of +V, Vcc, Vdd, Vss, and GND is giving me a bit of grief.  For example:  I

usually specify +V as the incoming power to the circuit.  Then into the

voltage regulator.  Out of the regulator, I'm faced with the task of

delivering the regulated voltage to my various devices.  Some devices want

Vcc and GND.  Some devices want Vdd and Vss, or some other combination.

Sometimes I power things with the UNregulated buss.  I thought that I could

just add the proper feeds to the downstream side of the regulator or where

ever I want to tap the power, but the ERC just goes nuts, saying that such

and such is overwritten by more than one signal, etc.  Same with the

grounds and/or 0V.  What am I doing wrong?  I've read the parts of the

manual that deal with these concepts over and over again, but I'm just not

getting it.

 

Thanks, Richard

Hi Richard, don't go down to the electron flow of electricity

Help Pin. Here you find about the DIRECTION of pins.

For power there is a general eagle direction: A battery has a SUPply

(call it output) of plus and minus, while an IC has PWR (Power)for its

supply (call that an input). The polarity has nothing to do with it.

So a three terminal voltage regulator has just an input and an output.

You can name the output-net anyway you want, or just "clip" a suitable

supply symbol to it. If you have a schematic then activate layer 93

(pin) and you can see the pin direction of eagle devices.

Hope I could help.

--

Mit freundlichen Grüßen / With best regards

Joern Paschedag

rubyfocus wrote on Tue, 26 April 2011 05:13

The only concept that's still giving me fits is the PWR and SUP pins.

Yes, the documentation is confusing at best.  The fact that "power pin" and

"supply pin" are pretty much interchangable in the world outside Eagle

doesn't help.  Eagle is a nice program, but it's choice of names is

downright broken in various places.

Basically supply should be used for things like ground symbols.  Connecting

a supply pin to a net in the schematic effectively overrides the net name

from the supply pin's name in the library.

Use power for pins of a IC that need to be connected to power or ground.

Unfortunately the ERC check will complain if a power pin is connected to a

net that has a different name than itself.  This is a well known Eagle

stupidity which hopefully will be fixed some day.  For example, you might

quite reasonably connect a microcontroller Vss pin to a net named GND, or a

Vdd pin to "5V", but Eagle will complain about the discrepancy.  This is

just one of the things you have to get used to.

Even worse is that Eagle will implicitly make connections based on the

names.  I don't remember the exact rules, but I think supply pins are

automatically connected to nets of their names even if you don't connect

them.  This is just asking for trouble, but Cadsoft has so far refused to

fix it.

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

On 04/26/2011 03:06 PM, Olin Lathrop wrote:

rubyfocus wrote on Tue, 26 April 2011 05:13

>> The only concept that's still giving me fits is the PWR and SUP pins.

 

Yes, the documentation is confusing at best.  The fact that "power pin" and

"supply pin" are pretty much interchangable in the world outside Eagle

doesn't help.  Eagle is a nice program, but it's choice of names is

downright broken in various places.

 

Basically supply should be used for things like ground symbols.  Connecting

a supply pin to a net in the schematic effectively overrides the net name

from the supply pin's name in the library.

 

Use power for pins of a IC that need to be connected to power or ground.

Unfortunately the ERC check will complain if a power pin is connected to a

net that has a different name than itself.  This is a well known Eagle

stupidity which hopefully will be fixed some day.  For example, you might

quite reasonably connect a microcontroller Vss pin to a net named GND, or a

Vdd pin to "5V", but Eagle will complain about the discrepancy.  This is

just one of the things you have to get used to.

 

Even worse is that Eagle will implicitly make connections based on the

names.  I don't remember the exact rules, but I think supply pins are

automatically connected to nets of their names even if you don't connect

them.  This is just asking for trouble, but Cadsoft has so far refused to

fix it.

I vastly prefer to call out power pins explicitly on symbols, and to

make them passive.  This side steps the whole "Eagle knows it's smarter

than me" routine, it gives me the flexibility I need to put parts on

different power rails (e.g. when I'm using a 'logic' part in an analog

circuit, or when I have both 5V and 3V supplies), and it puts power pins

out in front of anyone reading my schematics, so they know what's

going on, too.

--

Tim Wescott

Wescott Design Services

Voice: 503-631-7815

Cell:  503-349-8432

http://www.wescottdesign.com

On 5/2/2011 10:43 AM, Tim Wescott wrote:

On 04/26/2011 03:06 PM, Olin Lathrop wrote:

>> rubyfocus wrote on Tue, 26 April 2011 05:13

>>> The only concept that's still giving me fits is the PWR and SUP pins.

>>

>> Yes, the documentation is confusing at best. The fact that "power pin"

>> and

>> "supply pin" are pretty much interchangable in the world outside Eagle

>> doesn't help. Eagle is a nice program, but it's choice of names is

>> downright broken in various places.

>>

>> Basically supply should be used for things like ground symbols.

>> Connecting

>> a supply pin to a net in the schematic effectively overrides the net name

>> from the supply pin's name in the library.

>>

>> Use power for pins of a IC that need to be connected to power or ground.

>> Unfortunately the ERC check will complain if a power pin is connected

>> to a

>> net that has a different name than itself. This is a well known Eagle

>> stupidity which hopefully will be fixed some day. For example, you might

>> quite reasonably connect a microcontroller Vss pin to a net named GND,

>> or a

>> Vdd pin to "5V", but Eagle will complain about the discrepancy. This is

>> just one of the things you have to get used to.

>>

>> Even worse is that Eagle will implicitly make connections based on the

>> names. I don't remember the exact rules, but I think supply pins are

>> automatically connected to nets of their names even if you don't connect

>> them. This is just asking for trouble, but Cadsoft has so far refused to

>> fix it.

 

I vastly prefer to call out power pins explicitly on symbols, and to

make them passive. This side steps the whole "Eagle knows it's smarter

than me" routine, it gives me the flexibility I need to put parts on

different power rails (e.g. when I'm using a 'logic' part in an analog

circuit, or when I have both 5V and 3V supplies), and it puts power pins

out in front of anyone reading my schematics, so they know what's

going on, too.

 

same here. standard operating procedure.

On 5/2/2011 10:43 AM, Tim Wescott wrote:

On 04/26/2011 03:06 PM, Olin Lathrop wrote:

>> rubyfocus wrote on Tue, 26 April 2011 05:13

>>> The only concept that's still giving me fits is the PWR and SUP pins.

>>

>> Yes, the documentation is confusing at best. The fact that "power pin"

>> and

>> "supply pin" are pretty much interchangable in the world outside Eagle

>> doesn't help. Eagle is a nice program, but it's choice of names is

>> downright broken in various places.

>>

>> Basically supply should be used for things like ground symbols.

>> Connecting

>> a supply pin to a net in the schematic effectively overrides the net name

>> from the supply pin's name in the library.

>>

>> Use power for pins of a IC that need to be connected to power or ground.

>> Unfortunately the ERC check will complain if a power pin is connected

>> to a

>> net that has a different name than itself. This is a well known Eagle

>> stupidity which hopefully will be fixed some day. For example, you might

>> quite reasonably connect a microcontroller Vss pin to a net named GND,

>> or a

>> Vdd pin to "5V", but Eagle will complain about the discrepancy. This is

>> just one of the things you have to get used to.

>>

>> Even worse is that Eagle will implicitly make connections based on the

>> names. I don't remember the exact rules, but I think supply pins are

>> automatically connected to nets of their names even if you don't connect

>> them. This is just asking for trouble, but Cadsoft has so far refused to

>> fix it.

 

I vastly prefer to call out power pins explicitly on symbols, and to

make them passive. This side steps the whole "Eagle knows it's smarter

than me" routine, it gives me the flexibility I need to put parts on

different power rails (e.g. when I'm using a 'logic' part in an analog

circuit, or when I have both 5V and 3V supplies), and it puts power pins

out in front of anyone reading my schematics, so they know what's

going on, too.

 

same here. standard operating procedure.