How-To: Design your own iPod super dock (Part 3)
We're back again with our continuing iPod super dock how-to series (see parts one and two, if you need to catch up). Last week we layed out the schematic for the board, and today we'll do a check up on the schematic, and design the PC board that we'll make for our super dock. We're getting close now, can you smell it? It's solder.
Before we get started, you might want to download our latest bundle of project files. Inside the zip file you'll find a copy of the connector library and the complete schematic we made last week.
Before we make the board, we'll double check for any wiring problems on the schematic. Clicking on Tools then Erc checks the schematic for electrical problems.
In this case, we're not using the T1 or R1 pins on the MAX232. The two power errors are because we didn't follow the EAGLE power and ground conventions. Again, no big deal. If you have any "nets" that aren't fully connected, you'll get warnings about them here. Even with our "errors" we're good to go.
To create the board, click the not so obvious 'board' button next to the drop down in the tool bar.
EAGLE will as you if you want to create the board from the schematic. Click Yes.
The new window will be black, with the various components sitting to the side. The white outline represents the actual PC board. Everything in this view is movable. If you make a mistake, remember that in EAGLE alt-backspace is undo. You get several undo steps, so feel free to mess around.
Drag the dock connector over to the edge of the board and place it. This is where the nice outline of the connector we created comes in handy. The yellow lines represent the connections that will be made to all the other components from the schematic.
Don't worry if you get this error. In the board view, it just means you tried to move or rotate a part off the board outline. Try it again placing it within the outline of the board. Alternatively, you can make the board really, really big and shrink it down later.
Play with the board layout until you get something you're happy with. We put all of the AV connections on one edge and the data connectors on the opposite. Take your time. Keep in mind that each yellow line will eventually become a trace. Life's easier if you remember the Ghost-Busters motto: Don't cross the streams.
In case you're wondering where the power connector is, we plan to use a spare firewire cable along with our iPod wall charger. That way we can't accidentally inject extra juice to our computer's FireWire ports.
Once you're happy, click Tools and Auto to pull up the options for routing the board. The auto router is one of the fantastic features of EAGLE. The software will play connect the dots to achieve a reasonably efficient trace layout. If it doesn't completely succeed the first time, don't worry. Keep reading.
To get the board to route completely, we had to take the grid to 15 mil. This is pretty fine, but we'll tweak the routing once the computer takes a shot at it. The option to set this pops up when the Auto command is used.
This is a slightly modified auto generated layout. At this point we'd made just a few changes. If you're curious, the fatter traces are replacements. We used them where they'd fit, and they'll be easier to etch later on. Red denotes top layer traces, blue the bottom.
A few tips on tweaking traces: With a trace selected, clicking the middle mouse button will change the layer that the trace lives on. To keep the signal, you'll need "via." Sometimes EAGLE will add them, but you may need to do it by hand.
Here we've moved all the through hole connections (but one) to the bottom layer for ease of construction. Laying out a nice PC board is really an art. This is our result after a few hours of tweaking until we were pretty happy. We made loads changes to the computer generated board. Don't be surprised if the ultimate version ends up a bit different.
Next time we'll bring all the pieces together and finish our super dock. The traces on our board are pretty fine for the usual home PC board making techniques; we'll test out a few and let you know what gives the best results for making your own. See you next week!
