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Connect two different NETs

MaxKielland

This isn't that simple as it first sounds. Assume the following scenario.

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The red signal, LOAD+ is dimensioned for 10A but the green signal, Feed back, is going to an OP-AMP and only needs a few mA. Is there any way I can connect these two nets without automatically rename one of them?

 

Do I really have to put in a 0 resistor because of limitations in EAGLE?

  • 0

    Max Kielland wrote on Thu, 27 March 2014 09:00

    This isn't that simple as it first sounds. Assume the following

    scenario.

    The red signal, LOAD+ is dimensioned for 10A but the green signal,

    Feed

    back, is going to an OP-AMP and only needs a few mA. Is there any way

    I

    can connect these two nets without automatically rename one of them?

     

    Do I really have to put in a 0 resistor because of limitations in

    EAGLE?

     

     

    A net is a net. When you connect two wires they are the same net, by

    definition. It cannot have two names.

     

    Simply use the TEXT tool to write 'Feedback' if you desire those words at

    that point.

     

    HTH

    Warren

    --

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

     

  • 0 in reply to autodeskguest

    On 26/03/14 22:59, Warren Brayshaw wrote:

    Max Kielland wrote on Thu, 27 March 2014 09:00

    This isn't that simple as it first sounds. Assume the following

    scenario.

    The red signal, LOAD+ is dimensioned for 10A but the green signal,

    Feed

    back, is going to an OP-AMP and only needs a few mA. Is there any way

    I

    can connect these two nets without automatically rename one of them?

     

    Do I really have to put in a 0 resistor because of limitations in

    EAGLE?

     

    A net is a net. When you connect two wires they are the same net, by

    definition. It cannot have two names.

     

    Simply use the TEXT tool to write 'Feedback' if you desire those words at

    that point.

     

    Alternatively, if you want to explicitly show on the schematic that the

    feedback net is only a low-current sense trace that should be connected

    locally to a particular point in the LOAD+ trace (e.g. to account for

    any losses in the copper) then you can create a virtual component with

    two (SMD) pads overlapping. Look for answers to how to connect analogue

    and digital ground planes at one point - it's the same basic problem of

    two nets connected.

     

     

  • 0

    On 03/26/2014 04:25 PM, Max Kielland wrote:

    This isn't that simple as it first sounds. Assume the following

    scenario.

    The red signal, LOAD+ is dimensioned for 10A but the green signal, Feed

    back, is going to an OP-AMP and only needs a few mA. Is there any way I

    can connect these two nets without automatically rename one of them?

     

    Max,

     

    As Rob mentioned, the best way to short two nets together is with a

    package that has two SMD's that overlap.  DRC will complain about the

    overlap, but since it is intentional, it can be safely approved.

     

    Attached is an abbreviated library providing an example of a short.

    Using the provided package as an example, you can create shorts with

    preferred widths and add them to the device.

     

    HTH,

        - Chuck

     

     

     

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  • 0

    Now when I read my own question a few days later I realize that I have been give too litle information. It isn't the Schematic that is the real "problem", it is the PCB routing. Since LOAD+ is dimensioned for 10A and the sense (feedback) only draws a few mA, I dont want (or can because of OP pin spacing) have it dimensioned for 10A.

     

    Making an overlapping land pad might be one solution to get "around" this problem. But if I have to accept the overlapping, I could just accept the feedback trace to be smaller than the 10A trace.

     

    Thanks to everyone contributing....

  • 0 in reply to MaxKielland

    Are you using the autorouter?  I've only routed manually, so I always choose an appropriate trace width myself...