Kicad, like most PCB design software does a few things to reduce the "clutter" on the circuit diagram. One of these things is to "hide" the power connections. This allows you to insert a couple of power port symbols on the circuit and they will automatically form the connections to the power connections of the same name.
One thing to note and that is if you have the show hidden pins selected eeschema left hand icon toolbar 5th one down, Then you have to connect them manually. On a device such as a 4 gate 7400 the power pins are normally shown on the "a" gate in the package. If you only have one or two packages on in your design it does not matter a great deal if you connect the power manually or not, but if you have lots of packages then you can see that using the hidden power pins system will make life a lot easier. To see where things are, you can also use the library editor, top toolbar 5th icon from left, select the 7400 as the part to edit. You will then see the power pins in grey (usually) which means that they are set to no draw, it also tells you that the power pin names are VCC and GND You will prob. find that things will start to go wrong when you do a DRC check, and it start complaining about power missing. Another wrinkle that confuses things at first is that power lines have to be "driven" this is fine if you have a device that is providing power out, but if not, sayyou have a board where the power is provided via a couple of leads from an external PSU you have to tell the system that the power pins are driven. You do this by adding a power flag to the power port lines. You have to add one to the GND line as well, that sounds a little odd as GND is not normally thought of as a power out, but it's the way the DRC thinks of it. Andy On Tue, 08 Sep 2009 06:23:37 -0000 "tom_iphi" <[email protected]> wrote: > Hi, > > my qestion is probably quite stupid: > > When I create a schematic with 7400 nand gates, I add the gates with the > place component function from the standard kicad 74xx library. But I never > get to see the power supply pins for the 7400 chip. How do I connect those > (VCC, GND)??? > > And, I have looked at the definition of the 7400 in libedit. Where are the > power supply pins defined there? I can only find the 4 gates. > > Thanks, Tom > > > > ------------------------------------ > > Please read the Kicad FAQ in the group files section before posting your > question. > Please post your bug reports here. They will be picked up by the creator of > Kicad. > Please visit http://www.kicadlib.org for details of how to contribute your > symbols/modules to the kicad library. > For building Kicad from source and other development questions visit the > kicad-devel group at http://groups.yahoo.com/group/kicad-develYahoo! Groups > Links > > >
