Below are my notes from the Eagle tutorial we got from Adam Setapen (thank you Adam!) - I've tried my best to organize them.
The Basics of Using Eagle
Eagle has a lot of built in libraries of components that you can use, but there are two for this class that you can download from the class site which contain all the components we'll need (the libraries are ng.lbr and fab.lbr).
in free version of eagle, don't put anything below or to the left of the cross (origin) in either schematic or layout!
Eagle has two windows that you use simultaneously to design a board:
schematic (.sch) - logical components
layout (.brd) for the actual board that we mill
there is a schematic/board button so you can switch between the two
don't close layout and not schematic (or vice versa) - need to keep both open all the time!!!
Eagle has a command line; basic commands include:
move = moves an item
net = makes a logical connection
junction = adds a junction (see more on junctions below)
value = addes value to components (i.e. ohm rating)
name = names a component
label = displays the name of a component in Schematic view
copy = copies an existing component on the schematic - be sure to rename pieces you copy!
add = opens up the libraries so that you can add components in Schematic view (note: always choose the 1206 components - these are the ones that have 12mm x 6mm packages
route = used in Layout view, this tells you if you need to add a connection (follow yellow lines)
ERC = electronic rules check; this ensures your board will actually work (use in Schematic view)
DRC = design rules check (in Layout) - keep all the default settings (16 mil is fine); it should display a "no error" message in the bottom left hand corner of the screen
group = groups components in Layout view together; if you right-click, then you can choose Move: Group to move the grouping
rats = in Layout view, tells you if you have airwires
rip = deletes connections in layout
show = after typing this, select a component to see information about it displayed in the bottom left corner of the screen. Also, if you type show + [name of component] you can see that component highlighted. You can use this to see all the ground traces, for example.
text = allows you to add text to your board! (You can also edit the exported .png file in Photoshop to give text and images more flare!)
info = then click on text to get properties of the text
avrisp header is for programming the board (on every board we make)
microcontroller on every board
FTDI header allows board to talk to computer
put a capacitor between voltage and ground (take it for granted that we always need it)
resistor between reset pin on microcontroller and VCC is a pullup resistor; pulls reset pin high whenever not set
any signal can be:
high impedence (not connected to anything; floating pin) - the pullup resistor keeps pin high
once the microcontroller is programmed, its stored in non-volatile memory - don't have to do it again
20MHz resonator (crystal) is a clock
ATTiny has a 8Mhz clock but the crystal is faster and so the microcontroller can work faster
all GND should be connected otherwise you don't know what 0 voltage is for a component
when you power an LED with 5V, they're only rated for 3V, so add a power-limiting resistor before OR after it - 500 to 1000 ohms (500 ohms to 1K ohms)
can look up data sheet (use the component number in HTMAA inventory page to find the part on Digikey which stores all data sheets)
current flows in direction of diode arrow
LEDs don't have to have values - you can just approve this error
OMRON switch is the button we want (6mm package)
button needs to have a resistor to pull up pin that its connected to! (10K for pullup resistors)
on button, 1 and 2 are internally connected (same for 3 and 4)
0 ohm resistor trick: place a 0 ohm resistor over a trace to hop over an existing trace
Designing a Board
to connect two components, NET -- NAME -- LABEL (so you'll need a net on both the component itself and the microcontroller pin as well)
if it asks you if you want to name something with a name that's already been used, it connects those two leads
junction (symbol is a dot) can be useful when a net splits into two different nets - indicates whether two nets that crossover are connected or not...
under options you can change the background color of the schematic/layout (User Interfaces)
click on display to see the layers which you can show/hide
layout pieces in Layout - use right-click to rotate stuff
Exporting a Board Design to be Used with Modela
to prep board for manufacture, in layers window, only show top layer (traces only)
then export as a png (file -- export -- image)
settings should be MONOCHROME and 1000 DPI
then export Dimenson layer for milling the outside of the board
Remember: the Modela loves chocolate - it eats (cuts) chocolate (DARK) and leaves white!