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'[EE]: metric Eagle question!'
2002\12\11@223827 by Roman Black

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Hi, seems everytime I try to use the darn thing
I end up pulling my hair out and swearing in
multiple languages. :o}

When using Eagle to place SMD parts on a METRIC
grid, say 1mm spacing, the parts added to the
schematic are placed automatic on the PCB as a
vertical array, which is in f^&%#$ 0.1 inch
spacing. So every part added needs to be moved
painfully in hundredths of mm until it is aligned
correctly to the mm grid!!!

I think i've got every single variable adjusted
to mm, but the mongrel thing insists on adding
every new part on that stupid 0.1 inch spacing!
Any ideas? :o)
-Roman

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2002\12\12@004154 by Quentin

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>Any ideas? :o)
Don't use 1mm spacing. :)

It is the way the parts are made, they were created on 0.1 inch spacing,
so you will have fun lining them up on 1mm. try 1.27 mm or 0.635 mm spacing.
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2002\12\12@083113 by WernerS

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Roman,

Correct me if I'm wrong...

But as far as I know, all electronic components were/are originally based on
inches, with the default pin spacing being 0.1 inch (2.54mm). SMD
components, especially IC's, normally work on smaller pin spacing, such as
0.05 inches. I know SMD transistors seem to have odd spacing, but they all
have spacing that can be numbered within not-so-small inch numbers.

The best help I can provide, is to keep your Eagle running on inches, with a
small grid like 0.01 inches and zoom in closely to place the parts. Also,
when using the autorouter, you have to specify the routing grid as 10mil
(which is 0.01 inches) or smaller. This shouldn't be a problem, since SMD
boards normally use small parts with tiny legs and tracks so thin that you
have to send your design to a boardhouse.

Hope this helps

Werner Soekoe
WernerS(a)fsl.gov.za



{Original Message removed}

2002\12\12@083409 by Roman Black

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Quentin wrote:
>
>  >Any ideas? :o)
> Don't use 1mm spacing. :)
>
> It is the way the parts are made, they were created on 0.1 inch spacing,
> so you will have fun lining them up on 1mm. try 1.27 mm or 0.635 mm spacing.


Gee! Inches?? Now why didn't I think of that!
I'm so silly. ;o)

Now just for a moment assume that i've done
boards in inches for 25+ years, and for specific
reasons I have a LOT to gain by going to metric
and have spent some hours analysing my problems
with this change and solving most of them...

The last problem remains that Eagle insists on
INITIAL PLACING all parts on that mongrel 0.1
grid, even when I have the main grid and all
obvious options now set to mm.
-Roman

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2002\12\12@090449 by mark

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Hi,

I would tend to agree with Werner on this.  Having attended school in the post UK decimalisation era, I've grown up with metric and generally use metric in every "units of measurment" scenario.  In my case there are only two exceptions to this rule.  The first is road distances (where I'm just used to seeing signposts written in miles) and the other is PCB layout.  I too use Eagle for schematics and board design and soon realised that metric measurements were not really the way to go, given that electronic components are generally sized for an imperial world.  My own advice would be to use a grid measurement half the size of your smallest pitch - that will give you enough flexibility to do 80% of your layouts (unless they're hideously complex).  For the other 20%, keep halving the grid measurement until you get the required resolution.  For example, any 0.01" pitch boards that I'm working on my default grid setting would be 0.005".  For more detailed track layout I take this temporaril

Regards,
Mark Brown

>
> {Original Message removed}

2002\12\12@092949 by Alan B. Pearce

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>But as far as I know, all electronic components were/are
>originally based on inches, with the default pin spacing
>being 0.1 inch (2.54mm).

That has been the standard for many years, but you will find that a lot of
components are now heading for a 2.5mm standard, instead of 2.54mm,
especially connectors that originate in Japan :)) Not usually a problem for
small connectors, e.g. I have a 8 pin 2.5mm pitch connector fitted to pads
originally designed for a 2.54mm pitch connector, and get away with it
because of the hole sizes used.

Roman, what default grid have you set up? I don't use Eagle, so don't know
the settings, but just wonder what would happen if you set a 2.5mm defacto
setting if this is possible.

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2002\12\12@093954 by Spehro Pefhany

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At 02:08 PM 12/12/02 +0000, you wrote:
>Hi,
>
>I would tend to agree with Werner on this.  Having attended school in the
>post UK decimalisation era, I've grown up with metric and generally use
>metric in every "units of measurment" scenario.  In my case there are only
>two exceptions to this rule.  The first is road distances (where I'm just
>used to seeing signposts written in miles) and the other is PCB layout.  I
>too use Eagle for schematics and board design and soon realised that
>metric measurements were not really the way to go, given that electronic
>components are generally sized for an imperial world.  My own advice would
>be to use a grid measurement half the size of your smallest pitch - that
>will give you enough flexibility to do 80% of your layouts (unless they're
>hideously complex).  For the other 20%, keep halving the grid measurement
>until you get the required resolution.  For example, any 0.01" pitch
>boards that I'm working on my default grid setting would be 0.005".  For
>more detailed track layout I take this temporaril

We're still using Imperial measurements for PCBs, but I find that many or
even most components and virtually all *new* component footprints are now
hard metric. It takes more digits and is less accurate generally to enter a
metric measurement in Imperial units than the other way around (because
2.54 is exact and 1/2.54 is a repeating number). But, if they are within a
mil (thou) that's good enough, usually.

Does anyone have a clever way of automatically placing and orienting many
sequentially numbered parts from a spreadsheet or other similar data? If
so, what PCB package and how? I *think* there is a way using Protel's
reverse pick and place file capabilities, but it looks messy and seems not
to be well documented, at least in my demo version. This is to prevent the
necessity of manually keying in scores or hundreds of 5 digit
random-looking numbers with perfect accuracy.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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2002\12\12@101507 by Quentin

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I am also a mm man. So I was not trying to convert you, just helping you
find a solution with a bit of tongue in cheek.
The problem with the Eagle parts is that the origin point is set on a
0.1 inch grid in relation with the pins, which are also set on the same
grid. So when you place the part on a millimeter grid, the origin will
snap to the grid but not the pins. The best is then to use the mm
equivalent of 0.1 inch or redo all your parts on a mm grid.
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2002\12\13@075037 by Roman Black

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Alan B. Pearce wrote:

> Roman, what default grid have you set up? I don't use Eagle, so don't know
> the settings, but just wonder what would happen if you set a 2.5mm defacto
> setting if this is possible.


Hi Alan, i've tired a number of grids, mainly
i'm using 1mm grid now with autorouting on both
tests of 0.25mm and 0.2mm, haven't decided which
router grid i'm going with yet. Probably 0.2mm
as I hate those mongrel 5s and the breeding of
decimal places you get by continual dividing by 2.
:o)
-Roman

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2002\12\13@080319 by Roman Black

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Spehro Pefhany wrote:

> We're still using Imperial measurements for PCBs, but I find that many or
> even most components and virtually all *new* component footprints are now
> hard metric.

Yep. :o) Not to mention that all the commercial
machines to do placement and solder paste dotting
and pcb routing all need the coords in mm.


> Does anyone have a clever way of automatically placing and orienting many
> sequentially numbered parts from a spreadsheet or other similar data? If
> so, what PCB package and how? I *think* there is a way using Protel's
> reverse pick and place file capabilities, but it looks messy and seems not
> to be well documented, at least in my demo version. This is to prevent the
> necessity of manually keying in scores or hundreds of 5 digit
> random-looking numbers with perfect accuracy.

Bingo. Exactly a good reason for the changes i'm
making. All my SMD parts are now placed on a mm
grid, so R1 is at (x,y) 12,9 and not 12.14,9.37...
Layout is easier, error checking is easier,
prepping files for placement machine is easier,
and in general the two days i've been testing it
has been an *absolute pleasure* to lay the PCB out
compared to all the past attempts in inches.

I wanted to avoid generic metric/imperial debating
but really an inch is about 25 times too big to be
the perfect SMD board measuring unit, and constantly
dividing pin standards and grids by 2 compounds an
already problematic measuring unit. Probably why
all the "proper" machines use mm I suppose.
-Roman

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2002\12\13@090939 by Roman Black

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part 1 1518 bytes content-type:text/plain; charset=us-ascii (decoded 7bit)

Quentin wrote:
>
> I am also a mm man. So I was not trying to convert you, just helping you
> find a solution with a bit of tongue in cheek.
> The problem with the Eagle parts is that the origin point is set on a
> 0.1 inch grid in relation with the pins, which are also set on the same
> grid. So when you place the part on a millimeter grid, the origin will
> snap to the grid but not the pins. The best is then to use the mm
> equivalent of 0.1 inch or redo all your parts on a mm grid.


Ok, the chips are on an inch-based grid. But the
SMD discretes are not, they have two or 3 connections
and tolerate large adjustments to pad size etc.
A 0805 is very close to 2mm x 1.2mm, and a 1206
is about 3mm x 1.6mm, or close enough that there
is no problem designing new library components with
pads and spacing in mm.

The board is laying out perfectly and a 0.25mm route
grid is very neat and will still neatly route a track
between the legs of a 0.1 inch DIP chip or neatly
between two 0805 pads.

Here is a picture of a test direct from the Eagle
autorouter with my new metric SMD parts and a SOIC,
every part is placed on a simple 1mm grid, routed at
0.25mm and is quite ok for a first auto-route. :o)
-Roman

PS. note the interaction of the metric route grid
with the imperial pin spacing on the IC.

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part 2 15125 bytes content-type:image/gif; name="1mm_25.gif" (decode)


part 3 2 bytes
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2002\12\13@093232 by Alan B. Pearce

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>1206 is about 3mm x 1.6mm,

Well metric made components that are equivalent to 1206 are known as 3216
:))

Our Orcad system has both descriptions in it, just to totally confuse the
novice. :)))

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2002\12\13@155300 by Peter L. Peres

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On Thu, 12 Dec 2002, Spehro Pefhany wrote:

*>We're still using Imperial measurements for PCBs, but I find that many or
*>even most components and virtually all *new* component footprints are now
*>hard metric. It takes more digits and is less accurate generally to enter a
*>metric measurement in Imperial units than the other way around (because
*>2.54 is exact and 1/2.54 is a repeating number). But, if they are within a
*>mil (thou) that's good enough, usually.

Imho the reason is that China, the main manufacturer of consumer
grade components , is a METRIC country.

Peter

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2002\12\13@160104 by Spehro Pefhany

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At 09:53 PM 12/13/02 +0200, you wrote:
>On Thu, 12 Dec 2002, Spehro Pefhany wrote:
>
>*>We're still using Imperial measurements for PCBs, but I find that many or
>*>even most components and virtually all *new* component footprints are now
>*>hard metric. It takes more digits and is less accurate generally to enter a
>*>metric measurement in Imperial units than the other way around (because
>*>2.54 is exact and 1/2.54 is a repeating number). But, if they are within a
>*>mil (thou) that's good enough, usually.
>
>Imho the reason is that China, the main manufacturer of consumer
>grade components , is a METRIC country.

Assuming you are talking about mainland China, I don't think she has yet
originated standards in many, if any, components- they are virtually all
originally Japanese with some SE Asian.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spamBeGonespeffspamBeGonespaminterlog.com             Info for manufacturers: http://www.trexon.com
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2002\12\14@160430 by Peter L. Peres

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On Fri, 13 Dec 2002, Spehro Pefhany wrote:

*>At 09:53 PM 12/13/02 +0200, you wrote:
*>>On Thu, 12 Dec 2002, Spehro Pefhany wrote:
*>>
*>>*>We're still using Imperial measurements for PCBs, but I find that many or
*>>*>even most components and virtually all *new* component footprints are now
*>>*>hard metric. It takes more digits and is less accurate generally to enter a
*>>*>metric measurement in Imperial units than the other way around (because
*>>*>2.54 is exact and 1/2.54 is a repeating number). But, if they are within a
*>>*>mil (thou) that's good enough, usually.
*>>
*>>Imho the reason is that China, the main manufacturer of consumer
*>>grade components , is a METRIC country.
*>
*>Assuming you are talking about mainland China, I don't think she has yet
*>originated standards in many, if any, components- they are virtually all
*>originally Japanese with some SE Asian.

China, ex-USSR and all former coutries that used to belong to COCOM used
metric versions of all parts that you care to think of for MANY years.
This includes metric versions of nearly all TTL chips (Russian made ones I
know of)  (using 2.5 mm instead of 2.54mm as modulus). Maybe some of the
guys in those areas can comment.

As to standards, one produces what the market asks for. Since many
products leave mainland China ready assembled they can well be metric
inside. This is probably more of a historical thing now but it used to be
so that you had to bend pins to get a 2.5mm MCU susbstitute to fit a
2.54mm modulus board design ... fortunately only chips with relatively few
pins were made that way (with 2.5mm modulus) afaik.

Peter

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