Eagle PCB question

Forum 2005-2010 (read only) Hardware Development
1

Bah! Eagle is like brilliant one minute and totally frustrating the next!

I'm using the auto router which I know people say don't bother but I'm new to PCB design and having scaled the initial learning curve with Eagle I want to spend my time on making my projects for a bit not learning software! I know I'll be rewarded with further study and I will do so later.

Using default.dru none of my designs are too complex that the auto router doesn't do a quick job without any airwires. Thing is I'm doing homebrew boards and the standard settings are too fine for etching/drilling, or at least with my current skills! I found some article with a hobby.dru which is what I used to make my first board (a MIDI interface) but for my second board (which includes a 14 pin IC, a 16 pin IC, a 24 pin IC, three diodes, a resistor network, a resistor, a 2x4 pin header and 12 4x1 pin headers!) the settings are too much the other way and Eagle just can't fit everything on reasonable sized board without airwires.

So I've been fiddling with the values in the DRC which seem to guide the autorouter and they certainly make a difference ... but I'm not sure what that difference is!

How do I specify fixed sizes for traces (top and bottom) and for vias? What I want to be able to do is move things around, change board size and hit autorouter and see if it finishes at 100%. If not then tweak values and try again until I get a board which I reckon can be etched without breaks in the copper etc. If I fiddle enough I get the trace widths to change but the via sizes don't seem to budge. I did find something on Google where I could use the command line to change all the via sizes but that was once the board was routed and collisions resulted and ripping up all the traces and re-autorouting didn't remember those new values.

Thanks
Jim

2

I'm new to eagle as well! I've found that sometimes rotation or position can be the difference between a design that the autorouter manages well to a definite fail.

If you click on the 'rats nest' button the yellow 'wires' will 'rethink' and connect to its nearest neighbour. Less crossing lines is better.

[someone more knowledgeable should probably disagree with something I said] ::slight_smile:

Good luck!

3

Hey Jim-

I'm not sure this is 100% correct, but I use "Net Classes" for this (this is on the Edit menu). I usually add a class for both GND and 5V as well as changing the default Width.

I hope this helps,

Brad.

4

Did you read the "instructable" that goes with "hobby.dru" ?

I thought I was pretty detailed in describing which parameters did what...

5

Possibly! If I did it leaked out of my crowded brain. I will revisit it .. or maybe I got hobby.dru somewhere else come to think of it .. ?

I think I've worked it out anyway. The vias are defined relative to the size of their drill hole. I tweaked something anyway and all my vias went HUGE! Nearly there ... :slight_smile: