Please Help!

Hi Michael,

It looks like on the schematic, the pins are actually not connected to the green wires, they are just "close" to the green wires.

You can test by trying to move a component. If the component moves but the wires do not move along with the component, then they are not connected.

The giveaway would be this:

It should not be possible to have blobs so close to each other, unless you've modified the grid setting:

Basically, on the schematic view, you should never change the grid setting from the default (0.1inch). All components are/should be designed such that they can be wired up using the default grid setting.

You should only need to modify the grid setting on the board view, or when creating parts.

I want the default in metric not American standard. How do I change the default to metric? Also, if I create the parts in metric, they won't get connected on the schematic when American standard is used.

Thank you,

Mike

Hi Michael,

A component (device) comprises of the symbol (i.e. logical representation) and the package (physical representation).

All EAGLE components use a symbol in imperial measurement system. The package can be metric or imperial.

For the schematic (which is a logical view, not physical) it doesn't really matter what the unit is, except that the component symbols must also be created with the same unit.

As mentioned, all the existing symbols are based on a 0.1inch grid, so it's unfeasible to change this unless you're prepared to manually create every schematic symbol you'll ever need.

On your physical board view, you can change to metric if you wish, using the grid icon.

Your final PCB certainly can use some parts that are dimensioned metric and others that may be imperial. This is normal practise; some component manufacturers dimension in metric (e.g. 1mm), others dimension in imperial (e.g. 0.05inch) and metric (e.g. 1.27mm).

Well, my thinking is that I've noticed that the data sheet for nearly all components are listed in metric so it makes sense to me to use metric to make the parts I need rather than always converting everytime I need to create a part. You said the component symbol needs to be created in the same measurement as the schematic not the package?

By the way, your tip on moving the part to see if the wire is connected worked. I found that moving the part and making sure that the pin was on top of the wire before clicking again connects them.

Thanks for your quick reply,

Mike

A datasheet only specifies dimensions for the physical part, e.g. this capacitor:

However, the logical symbol (schematic symbol) for a capacitor is dimensionless, e.g.:

There is no datasheet that defines dimensions for a schematic symbol; it is like trying to put a linear dimension on a music note on a music sheet (the music sounds the same regardless of the size of the music sheet).

It just happens that for drawing purposes, the schematic symbol in EAGLE is always specified in inches grid; it's not 'right' or 'wrong', it's just that a unit is required due to the implementation. You're strongly advised (but not forced) to use inches, since then you can make use of the existing schematic symbols in EAGLE, rather than reinvent the wheel. Otherwise, if you really want metric on a schematic (why?), you could try to set the grid to 2.54mm (I personally wouldn't try this, because of rounding errors which may cause big problems on a spread-out schematic layout).

For physical symbols (package), it's a different matter: you're free to (and should) define the physical symbol in metric or imperial, whichever suits the component/datasheet.

Ah, I gotcha. I've got the board routed now.

Thanks for your help,

Mike