Eagle ERC questions

[Kevin-40]

Hi,

Been a while since I posted. Anyway, I am designing a board
in Eagle, and when I do an ERC check on the schematic I get
this error.

SUPPLY pin GND overwritten with more than one signal(H-GND,
GND)

I changed the net class for those pins to be H-GND for a
heavier trace width. I am not sure where it's getting the
GND signal from ?

I tried the archives and google, etc... but no luck. I basically
  have the GND pins on the M33887
chip tied to a GND symbol and then changed the net class to
H-GND so that it  has the track width set at 60 mils with 15
mils of clearence.

Thanks,
Kevin
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[Bob Blick-4]

Hi Kevin,

I'm relabeling this [EE] since it fits better there and you'll get a
wider audience.

Kevin wrote:

> Hi,
>
> Been a while since I posted. Anyway, I am designing a board
> in Eagle, and when I do an ERC check on the schematic I get
> this error.
>
> SUPPLY pin GND overwritten with more than one signal(H-GND,
> GND)
>
> I changed the net class for those pins to be H-GND for a
> heavier trace width. I am not sure where it's getting the
> GND signal from ?
>
> I tried the archives and google, etc... but no luck. I basically
>   have the GND pins on the M33887
> chip tied to a GND symbol and then changed the net class to
> H-GND so that it  has the track width set at 60 mils with 15
> mils of clearence.
>
> Thanks,
> Kevin

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[Kevin-40]

Thanks Bob.

I basically have five net classes in Eagle v5.1
signal,gnd20,gnd40,pwr20, and pwr40.
The gnd20 goes to the logic chips, and the gnd40 goes to the
motor control chip.
If I use the INFO command I can change NET CLASS, but not the NET NAME.
It says to use the NAME command to change the name.
If I use the NAME command it won't let me use the NET NAME I want it says
already in use and tries to connect the NET class with the old name.

I just wanted to run heavier tracks (40mil) for the 12V motor chip and 20
mil for the logic chips.

Can I do this in Eagle ?  I tried an old v4.15 but, it says I need at
least v4.60 to open the schematic.

Thanks,
Kevin

> Hi Kevin,
>
> I'm relabeling this [EE] since it fits better there and you'll get a
> wider audience.
>
> Kevin wrote:
>> Hi,
>>
>> Been a while since I posted. Anyway, I am designing a board
>> in Eagle, and when I do an ERC check on the schematic I get
>> this error.
>>
>> SUPPLY pin GND overwritten with more than one signal(H-GND,
>> GND)
>>
>> I changed the net class for those pins to be H-GND for a
>> heavier trace width. I am not sure where it's getting the
>> GND signal from ?
>>
>> I tried the archives and google, etc... but no luck. I basically
>>   have the GND pins on the M33887
>> chip tied to a GND symbol and then changed the net class to
>> H-GND so that it  has the track width set at 60 mils with 15
>> mils of clearence.
>>
>> Thanks,
>> Kevin
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[William "Chops" Westfield]

On Jul 20, 2008, at 6:59 PM, kben@... wrote:

> Can I do this in Eagle ?  I tried an old v4.15 but, it says I need at
> least v4.60 to open the schematic.

The short answer is "no."  It is a FAQ and an often-requested feature  
to allow one signal name to have multiple classes (especially analog  
vs digital gnd, and Power vs the short traces to fine-pitch SMT  
pins), but the "one class per signal" bit seems to be very entrenched  
in the design, so it hasn't changed in a long time and doesn't look  
like it's likely that it WILL change in the foreseeable future.

The usual fixes involve various sorts of zero-ohm resistors used to  
connect the nets with the same potential but different names, or  
separate routing steps before and after changing the class  
definition, or manual routing, or living with lots of design rule  
warnings (one thing that IS possible in v5.x is to tell eagle to  
ignore certain warnings.)

BillW

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[Xiaofan Chen]

On Mon, Jul 21, 2008 at 1:07 PM, William Chops Westfield <westfw@...> wrote:

>
> On Jul 20, 2008, at 6:59 PM, kben@... wrote:
>
>> Can I do this in Eagle ?  I tried an old v4.15 but, it says I need at
>> least v4.60 to open the schematic.
>
> The short answer is "no."  It is a FAQ and an often-requested feature
> to allow one signal name to have multiple classes (especially analog
> vs digital gnd, and Power vs the short traces to fine-pitch SMT
> pins), but the "one class per signal" bit seems to be very entrenched
> in the design, so it hasn't changed in a long time and doesn't look
> like it's likely that it WILL change in the foreseeable future.

Hmm, do you know any EDA package to allow one net name to
have multiple Net Class associations? As far as I know, Altium P-CAD
does not allow that. Mentor Graphics Expedition Design Capature
does not allow that either.

> The usual fixes involve various sorts of zero-ohm resistors used to
> connect the nets with the same potential but different names, or
> separate routing steps before and after changing the class
> definition,

Last time we tried this with P-CAD and it did not work too well.

> or manual routing,

I believe this is the way to go.

>or living with lots of design rule
> warnings (one thing that IS possible in v5.x is to tell eagle to
> ignore certain warnings.)

We still use the design rules to check the creepage/clearance
between different Net Class. However, manual check is also
necessary. Sometimes we need to get the help from
Mechanical Engineers (inside Pro-Engineer) to check 3-D
distance.

Xiaofan
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[Kevin-40]

I'll look for the FAQ, I read the tutorials and did not see
an answer to my questions. But, maybe I am dense I don't want
one signal with multiple classes. I have two classes and two
signal names. I.E. I want all A-GND signals to use the GND40
(40mil) class and all D-GND signals to uses the GND20
(20mil) class. Surely this is possible ?

Regards,
Kevin

>
> On Jul 20, 2008, at 6:59 PM, kben@... wrote:
>
>> Can I do this in Eagle ?  I tried an old v4.15 but, it says I need at
>> least v4.60 to open the schematic.
>
> The short answer is "no."  It is a FAQ and an often-requested feature
> to allow one signal name to have multiple classes (especially analog
> vs digital gnd, and Power vs the short traces to fine-pitch SMT
> pins), but the "one class per signal" bit seems to be very entrenched
> in the design, so it hasn't changed in a long time and doesn't look
> like it's likely that it WILL change in the foreseeable future.
>
> The usual fixes involve various sorts of zero-ohm resistors used to
> connect the nets with the same potential but different names, or
> separate routing steps before and after changing the class
> definition, or manual routing, or living with lots of design rule
> warnings (one thing that IS possible in v5.x is to tell eagle to
> ignore certain warnings.)
>
> BillW
>
>

--
Kevin
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[Olin Lathrop]

> SUPPLY pin GND overwritten with more than one signal(H-GND,
> GND)

Eagle thinks the name of the net connected to a supply pin should be the
same as the name of the supply pin.  I think that's a silly rule and makes
the ERC less useful, but there is no way to shut it off that I know of.  You
just have to go thru all ERC warnings and make sure none of them are "real".


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[Olin Lathrop]

kben@... wrote:
> I basically have five net classes in Eagle v5.1
> signal,gnd20,gnd40,pwr20, and pwr40.
> The gnd20 goes to the logic chips, and the gnd40 goes to the
> motor control chip.

You are confusing net classes with the net name.  Each net can only have one
class and one name.  You can't assign one class to a part of a net and
another to the rest.

I usually use one of two solutions.  The first is to manually route critical
parts of nets.  You probably want to do this anyway if you need large
current capability since you don't want those tracks going all over the
place and you want to keep the current loops to a minimum and you have to
carefully think about ground offset voltages.  You can manually route with
any width and drill size regardless of the net class.  I usually manually
route all ground connections because I usually have a ground plane or pseudo
ground plane.  In those cases, I want each ground SMD pad with its own via
straight to the ground plane.  This is usually better for the signals and
makes subsequent routing easier.

The second method is to break up a logical net into multiple Eagle nets by
using "short" devices.  These are just copper with two connections.  I draw
them as a slightly thickened line on shematics.  To Eagle each side of the
short will be a different net.  This technique is particularly useful to
guarantee that the ground connection for some part of the circuit connects
at exactly one point that you can place to the rest of the circuit.  This
allows you, for example, to keep switching power supply loop currents
isolated and off the main ground plane.


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[Olin Lathrop]

Kevin wrote:
> I have two classes and two signal names.

But I thought you were trying to apply them to one net.  Each net can have
only one name and one class.


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[Kevin-40]

No, I have two nets, and two classes, with different signal
names.  It must be a bug in v5.1, or a prodedural error. I
was able to delete all my Digital Grounds and then change
the net and class to what I wanted.

Analog  GND, Net Name "A-GND", Net Class "GND40"
Digital GND, Net Name "D-GND", Net Class "GND20"

Regards,
Kevin


> Kevin wrote:
>> I have two classes and two signal names.
>
> But I thought you were trying to apply them to one net.  Each net can have
> only one name and one class.
>
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[Kevin-40]

Anybody know of a website or links to a cheap beacon system
for postion location for a mobile robot ?  I looked around
the net and everything was pretty expensive.

I was thinking of trying to use those cheap 315 mhz tx/rx
modules. I want to be able to postion an autonomous lawn
mower within 6 inches or so. I have an acre lot with a house in the
center so line of site is out.

I have a GPS receiver but that is only good to ten feet
with WAAS enabled.

Any other suggestions ?

Thanks,
Kevin

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[Eoin Ross]

Would a local version of WAAS work?

 Use two GPS modules, one fixed and the other mobile. Fixed unit transmits location to the mobile, and the mobile unit calculates relative position.

Any drift in the fixed unit should be seen by the mobile unit as well. (Unless due to drift of internal calcs in the GPS module)


>>> On 30 Jul 08 at 10:25, in message
<Pine.LNX.4.64.0807301018280.32109@...>, Kevin <kben@...>
wrote:

> Anybody know of a website or links to a cheap beacon system
> for postion location for a mobile robot ?  I looked around
> the net and everything was pretty expensive.
>
> I was thinking of trying to use those cheap 315 mhz tx/rx
> modules. I want to be able to postion an autonomous lawn
> mower within 6 inches or so. I have an acre lot with a house in the
> center so line of site is out.
>
> I have a GPS receiver but that is only good to ten feet
> with WAAS enabled.
>
> Any other suggestions ?
>
> Thanks,
> Kevin

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[Sean Breheny]

That should work to some degree but not down to 6 inches unless you
use specialized differential GPS equipment.

I'm afraid that there is no cheap way to do what you want, Kevin. It
is a pretty hard problem, especially without line of sight.

What I'd be inclined to do is use odometry on the wheels most of the
time and just have some system for updating the position at some known
points to get rid of drift. For example, you could place several known
position markers in the yard and make sure that the robot goes past
them at least once per 100 feet of travel or somesuch. Also, you could
use a line of sight positioning method and just use odometry to handle
the times when there is no line of sight.

A final possibility would be to place some markers around the yard
which could be seen by a camera on the robot. Depending on which ones
it sees at which locations it could figure out is location.

Sean


On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross <eross@...> wrote:

> Would a local version of WAAS work?
>
>  Use two GPS modules, one fixed and the other mobile. Fixed unit transmits location to the mobile, and the mobile unit calculates relative position.
>
> Any drift in the fixed unit should be seen by the mobile unit as well. (Unless due to drift of internal calcs in the GPS module)
>
>
>>>> On 30 Jul 08 at 10:25, in message
> <Pine.LNX.4.64.0807301018280.32109@...>, Kevin <kben@...>
> wrote:
>
>> Anybody know of a website or links to a cheap beacon system
>> for postion location for a mobile robot ?  I looked around
>> the net and everything was pretty expensive.
>>
>> I was thinking of trying to use those cheap 315 mhz tx/rx
>> modules. I want to be able to postion an autonomous lawn
>> mower within 6 inches or so. I have an acre lot with a house in the
>> center so line of site is out.
>>
>> I have a GPS receiver but that is only good to ten feet
>> with WAAS enabled.
>>
>> Any other suggestions ?
>>
>> Thanks,
>> Kevin
>
>
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[alan smith]

what about just teaching it where to go?  You would (well..guess with any system) make sure the yard was free of debris, but you put it into learn mode, take it around its path once, then have it repeat it each time.  It would have to start at the same place each time but now you just have it programmed to go for x feet, turn so many degrees, go again x feet, etc.

Not as fancy, but might be easier to get the job done?

--- On Wed, 7/30/08, Sean Breheny <shb7@...> wrote:

> From: Sean Breheny <shb7@...>
> Subject: Re: [EE] Beacon system for position location
> To: "Microcontroller discussion list - Public." <piclist@...>
> Date: Wednesday, July 30, 2008, 9:03 AM
> That should work to some degree but not down to 6 inches
> unless you
> use specialized differential GPS equipment.
>
> I'm afraid that there is no cheap way to do what you
> want, Kevin. It
> is a pretty hard problem, especially without line of sight.
>
> What I'd be inclined to do is use odometry on the
> wheels most of the
> time and just have some system for updating the position at
> some known
> points to get rid of drift. For example, you could place
> several known
> position markers in the yard and make sure that the robot
> goes past
> them at least once per 100 feet of travel or somesuch.
> Also, you could
> use a line of sight positioning method and just use
> odometry to handle
> the times when there is no line of sight.
>
> A final possibility would be to place some markers around
> the yard
> which could be seen by a camera on the robot. Depending on
> which ones
> it sees at which locations it could figure out is location.
>
> Sean
>
>
> On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross
> <eross@...> wrote:
> > Would a local version of WAAS work?
> >
> >  Use two GPS modules, one fixed and the other mobile.
> Fixed unit transmits location to the mobile, and the mobile
> unit calculates relative position.
> >
> > Any drift in the fixed unit should be seen by the
> mobile unit as well. (Unless due to drift of internal calcs
> in the GPS module)
> >
> >
> >>>> On 30 Jul 08 at 10:25, in message
> >
> <Pine.LNX.4.64.0807301018280.32109@...>,
> Kevin <kben@...>
> > wrote:
> >
> >> Anybody know of a website or links to a cheap
> beacon system
> >> for postion location for a mobile robot ?  I
> looked around
> >> the net and everything was pretty expensive.
> >>
> >> I was thinking of trying to use those cheap 315
> mhz tx/rx
> >> modules. I want to be able to postion an
> autonomous lawn
> >> mower within 6 inches or so. I have an acre lot
> with a house in the
> >> center so line of site is out.
> >>
> >> I have a GPS receiver but that is only good to ten
> feet
> >> with WAAS enabled.
> >>
> >> Any other suggestions ?
> >>
> >> Thanks,
> >> Kevin
> >
> >
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[Detrick Merz]

I'm no RFID engineer, but along these lines, what about scattering
some RFID tags about the area it would be roaming in?  In most areas,
have the tags spread in low density (*several* feet/yard/meters
apart).  As you sense different tags coming and going, you know your
relative position.  In the areas where you need high precision, bury a
few tags separated by some known distance (a small grid, maybe 3x3, of
tags).  If you're picking up all 9 tags in a small grid, you're pretty
well on top of it... if you're only getting a few tags, you're off to
the side (and which side you're off to depends on which tags you can
read).

On Wed, Jul 30, 2008 at 12:03 PM, Sean Breheny <shb7@...> wrote:
<snip>
>
> A final possibility would be to place some markers around the yard
> which could be seen by a camera on the robot. Depending on which ones
> it sees at which locations it could figure out is location.
>
> Sean
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[Eoin Ross]

I'm not sure that it wouldn't work down to 6" or better. There's probably some assumptions I'm making that aren't right? Probably in the area of what resolution you can get out of cheaper GPS modules (I think I answered myself)

 Basically the system would be a roll-your-own DGPS - The 'fixed' part would have to be just that - never moving in your yard.
 It will give you some co-ordinates that will drift - but over 2-3 acres (?) I'd imagine an identical GPS unit would have almost identical position drift.

In the mobile unit you get the co-ordinates of the fixed unit, take your local co-ordinates, and calculate the offset - there's your position relative to 'home'

>>> On 30 Jul 08 at 12:03, in message
<e726f69f0807300903x6b051027l22b2fd1d658d46ad@...>, "Sean Breheny"
<shb7@...> wrote:

> That should work to some degree but not down to 6 inches unless you
> use specialized differential GPS equipment.
>
> I'm afraid that there is no cheap way to do what you want, Kevin. It
> is a pretty hard problem, especially without line of sight.
>
> What I'd be inclined to do is use odometry on the wheels most of the
> time and just have some system for updating the position at some known
> points to get rid of drift. For example, you could place several known
> position markers in the yard and make sure that the robot goes past
> them at least once per 100 feet of travel or somesuch. Also, you could
> use a line of sight positioning method and just use odometry to handle
> the times when there is no line of sight.
>
> A final possibility would be to place some markers around the yard
> which could be seen by a camera on the robot. Depending on which ones
> it sees at which locations it could figure out is location.
>
> Sean
>
>
> On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross <eross@...> wrote:
>> Would a local version of WAAS work?
>>
>>  Use two GPS modules, one fixed and the other mobile. Fixed unit transmits
> location to the mobile, and the mobile unit calculates relative position.
>>
>> Any drift in the fixed unit should be seen by the mobile unit as well.
> (Unless due to drift of internal calcs in the GPS module)
>>
>>
>>>>> On 30 Jul 08 at 10:25, in message
>> <Pine.LNX.4.64.0807301018280.32109@...>, Kevin <kben@...>
>> wrote:
>>
>>> Anybody know of a website or links to a cheap beacon system
>>> for postion location for a mobile robot ?  I looked around
>>> the net and everything was pretty expensive.
>>>
>>> I was thinking of trying to use those cheap 315 mhz tx/rx
>>> modules. I want to be able to postion an autonomous lawn
>>> mower within 6 inches or so. I have an acre lot with a house in the
>>> center so line of site is out.
>>>
>>> I have a GPS receiver but that is only good to ten feet
>>> with WAAS enabled.
>>>
>>> Any other suggestions ?
>>>
>>> Thanks,
>>> Kevin
>>
>>
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[Kevin-40]

Actually, that gives me another idea. I am not opposed to
any solution, just trying to find a cheap one :)  I have an
invisible fence for the dogs, so maybe I could have one
robot follow the invisible fence around the yard kind of
like a line following robot. Then that one could relay
course and heading to the lawn cutting robot. This would
allow line of site control.

I downloaded a couple of academic papers on beacons sysems
and it is definitly a non-trivial solution to the problem.

Thanks to all for the suggestions.

Regards,
Kevin



On Wed, 30 Jul 2008, Eoin Ross wrote:

> I'm not sure that it wouldn't work down to 6" or better. There's probably some assumptions I'm making that aren't right? Probably in the area of what resolution you can get out of cheaper GPS modules (I think I answered myself)
>
> Basically the system would be a roll-your-own DGPS - The 'fixed' part would have to be just that - never moving in your yard.
> It will give you some co-ordinates that will drift - but over 2-3 acres (?) I'd imagine an identical GPS unit would have almost identical position drift.
>
> In the mobile unit you get the co-ordinates of the fixed unit, take your local co-ordinates, and calculate the offset - there's your position relative to 'home'
>
>>>> On 30 Jul 08 at 12:03, in message
> <e726f69f0807300903x6b051027l22b2fd1d658d46ad@...>, "Sean Breheny"
> <shb7@...> wrote:
>> That should work to some degree but not down to 6 inches unless you
>> use specialized differential GPS equipment.
>>
>> I'm afraid that there is no cheap way to do what you want, Kevin. It
>> is a pretty hard problem, especially without line of sight.
>>
>> What I'd be inclined to do is use odometry on the wheels most of the
>> time and just have some system for updating the position at some known
>> points to get rid of drift. For example, you could place several known
>> position markers in the yard and make sure that the robot goes past
>> them at least once per 100 feet of travel or somesuch. Also, you could
>> use a line of sight positioning method and just use odometry to handle
>> the times when there is no line of sight.
>>
>> A final possibility would be to place some markers around the yard
>> which could be seen by a camera on the robot. Depending on which ones
>> it sees at which locations it could figure out is location.
>>
>> Sean
>>
>>
>> On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross <eross@...> wrote:
>>> Would a local version of WAAS work?
>>>
>>>  Use two GPS modules, one fixed and the other mobile. Fixed unit transmits
>> location to the mobile, and the mobile unit calculates relative position.
>>>
>>> Any drift in the fixed unit should be seen by the mobile unit as well.
>> (Unless due to drift of internal calcs in the GPS module)
>>>
>>>
>>>>>> On 30 Jul 08 at 10:25, in message
>>> <