4 Replies Latest reply on Apr 18, 2019 6:07 AM by fabboco

    Same net but different net class with Eagle

    fabboco

      I have a trace which powers an external device and with a large size because it carries a relative high current (more than 1A).

      Along this trace I have a small value resistor to monitor the flowing current.

      The resistor is connected to an ADC to measure current. The traces between the resistor and the ADC can be smaller than the power traces because not much current flows there.

      I am not able to use two different net classes for the power trace and for the ADC traces. A soon as I change the class of the power trace, the sensors traces get the same net class and viceversa.

      I have also tried to put a 0 ohm resistors along the sensor traces but this doesn't help neither.

      Can anyone help me with this issue?

      Thx

        • Re: Same net but different net class with Eagle
          Autodesk Guest

          On 4/16/19 2:38 AM, Fabrizio Boco wrote:

          tried to put a 0 ohm resistors along the sensor traces but this doesn't help neither.

          You have to use a different net name between 0 ohm and sense resistor so

          it can  have the different class.

          Paul R

           

          1 of 1 people found this helpful
          • Re: Same net but different net class with Eagle
            dukepro

            Fabrizio,

             

            Look in the shorts.lbr file.  It consists of two SMD pads that overlap. 

            By putting a short in series with your smaller resistor, it forms two

            different nets.  The net between the short and the resistor could be

            assigned a different class allowing the narrower trace.  I can send a

            shorts library to you.  Olin Lathrop is the original author, and I've

            added a couple of my own.  Olin has published it on the Internet, which

            is where I found it years ago.

             

            My primary use of shorts is to connect different grounds together.  i.e.

            I'll have a DGND, AGND, and HVGND representing grounds used in different

            areas of a design (digital, analog, and high voltage).  In the end, all

            these grounds need to be connected together.  I'll connect DGND to GND

            through a short, then AGND to GND, and HVGND to GND.  Just plain old GND

            will be routed back to the battery, or power supply or whatever.

             

            Of course, you could use the narrower trace just as you have it now. 

            When you do the DRC, you can approve the error it generates and it'll

            never bother you again... at least until you move it.

             

            HTH,

                - Chuck

             

             

            On 4/16/19 02:38, Fabrizio Boco wrote:

            I have a trace which powers an external device and with a large size because it carries a relative high current (more than 1A).

            Along this trace I have a small value resistor to monitor the flowing current.

            The resistor is connected to an ADC to measure current. The traces between the resistor and the ADC can be smaller than the power traces because not much current flows there.

            I am not able to use two different net classes for the power trace and for the ADC traces. A soon as I change the class of the power trace, the sensors traces get the same net class and viceversa.

            I have also tried to put a 0 ohm resistors along the sensor traces but this doesn't help neither.

            Can anyone help me with this issue?

            Thx

             

            --

            To view any images and attachments in this post, visit:

            https://www.element14.com/community/message/274385

             

             

            1 of 1 people found this helpful
              • Re: Same net but different net class with Eagle
                dukepro

                Fabrizio,

                 

                shorts.lbr can be found at

                http://www.diymodules.org/eagle-show-library?type=usr&id=1012210749&part=shorts.lbr

                 

                HTH,

                    - Chuck

                 

                 

                On 4/17/19 13:54, Chuck Huber wrote:

                Fabrizio,

                 

                Look in the shorts.lbr file.  It consists of two SMD pads that

                overlap.  By putting a short in series with your smaller resistor, it

                forms two different nets.  The net between the short and the resistor

                could be assigned a different class allowing the narrower trace.  I

                can send a shorts library to you.  Olin Lathrop is the original

                author, and I've added a couple of my own.  Olin has published it on

                the Internet, which is where I found it years ago.

                 

                My primary use of shorts is to connect different grounds together. 

                i.e. I'll have a DGND, AGND, and HVGND representing grounds used in

                different areas of a design (digital, analog, and high voltage).  In

                the end, all these grounds need to be connected together.  I'll

                connect DGND to GND through a short, then AGND to GND, and HVGND to

                GND.  Just plain old GND will be routed back to the battery, or power

                supply or whatever.

                 

                Of course, you could use the narrower trace just as you have it now. 

                When you do the DRC, you can approve the error it generates and it'll

                never bother you again... at least until you move it.

                 

                HTH,

                    - Chuck

                 

                 

                On 4/16/19 02:38, Fabrizio Boco wrote:

                I have a trace which powers an external device and with a large size because it carries a relative high current (more than 1A).

                Along this trace I have a small value resistor to monitor the flowing current.

                The resistor is connected to an ADC to measure current. The traces between the resistor and the ADC can be smaller than the power traces because not much current flows there.

                I am not able to use two different net classes for the power trace and for the ADC traces. A soon as I change the class of the power trace, the sensors traces get the same net class and viceversa.

                I have also tried to put a 0 ohm resistors along the sensor traces but this doesn't help neither.

                Can anyone help me with this issue?

                Thx

                 

                --

                To view any images and attachments in this post, visit:

                https://www.element14.com/community/message/274385

                 

                 

                1 of 1 people found this helpful
                • Re: Same net but different net class with Eagle
                  fabboco

                  Hi Chuck,

                  Thank you very much. That is exactly what I was looking for.