I am new to using the Eagle software. I’ve read all the tutorials I can find on it. I still have some questions though. When creating a board from the schematic do I have to create a ground and if so how would I go about doing this. This is something I should know being an EE major but on a PCB what exactly is a ground. Is it jsut a reference voltage? Another question, what is a good resistor from the library to sue. I jsut want the standard resistor package. Theres hundreds of them in my library and have no idea which one to pick.
Well for the ground, it depends on how you’re powering the board. For battery operated equipement, it’ll most likely be the negative terminal of the battery (unless you’re using a buck-boost or Cuk converter which flips the polarity). If it’s from a wall-wart, then it’ll be the negative terminal of that. If it’s from AC, then you’d have to have built the circuit and you should look for the return path.
As for Eagle… I dunno, I don’t use it, but you’ll probably get an answer soon.
well, it can be a reference voltage (ie. 0V). You will often hear the term gound plane which is basically a large area of the board that is connected to gnd. wikipedia sez: http://en.wikipedia.org/wiki/Ground_plane
in eagle, when I start laying out a board, I draw a ploygon that encompasses both sides of the PCB (if DS) and then name it GND. Then you place and route as you normally would. The gnd connection will be automatically made for you. You will see large areas of copper dedicated to gnd. This bascially helps to quiet down the higher frequency noise.
Choose your resistor package based off of what you need. There are tons of standard packages both SMT and through hole and Eagle has accounted for a lot of them. Pick the part you want to use then match it to what Eagle has available. If it isn’t in there, it really isn’t that difficult to make new parts once you run through the tutorial that you can download from http://www.cadsoft.de