Introduction

In the last tutorial you created a schematic. But is it any good? The electrical rules check, or ERC, is a useful way to debug your circuit. This example tutorial takes you through the process of finding and eliminating circuit design errors.

Resources

Steps

1. Open up the adjustable voltage regulator circuit from the previous tutorial.

   Prior Schematic

2. Go to inspect –> “electrical rules checker” in the menu.

   Open ERC

3. Select run and inspect the results. There should be two errors.

   Two Errors

   These errors indicate that the 12V and ground power connections are not connected to a source. Which is true! We forgot to add an external power connector to the board design, as in power from the wall or from an off-board battery!

4. These errors can be resolved by adding a power connector. Select add part

   Add Part

5. Search for “screw terminal” and select the 1x2 version (one row, two positions).

   Select a screw terminal

6. Place the screw terminal and wire it up

   Place part

   Wire it

7. Because the 12v and ground symbols are “power ports”, you can use as many of them as you want in your schematic, because they all signify the same thing, rather than a copy. So for the purposes of ERC, place a separate ground symbol (the same symbol as you used before) near the second pin of the screw terminal and wire it up.

   Add GND

   Wire GND

8. Run Annotations (assign reference designators)

   Run Annotations

9. Run ERC again

   Open ERC

   Run ERC

   See Errors

   Why are there still errors? The screw terminal pins are “passive” pins; they don’t indicate a power connection. To solve this you must explicitly state that pins 1 and 2 of the screw terminal are power outputs.

10. Double click on the screw terminal

    Open Symbol Properties

    1. Click Edit Symbol

       Editing a symbol of a built-in library directly from within a schematic will only impact that schematic; it will not be propagated back to the library.

    2. Change pin 1 and 2 to “power output” types

       Select Power Output

    3. Save and close the symbol editor window.

       Save Symbol

11. Re-run ERC one last time

    One Warning

    The one remaining warning indicates that you have locally edited a symbol within the schematic. This was intentional in our case, and can be ignored.

Delete Markers

You can delete the markers (little arrows in your schematic) generated by ERC by opening up the ERC tool and selecting the “delete markers” button

Delete Markers