I've got a design where I need to make a PCB in the shape of a donut. Circuits and components will be soldered on the donut and the center will allow objects to pass through. This brings up two questions:
How do I do internal routing? I've heard some PCB fabs don't allow internal routing.
How do I create a circular PCB (in EAGLE)?
Thanks a lot!
- How do I do internal routing? I've heard some PCB fabs don't allow internal routing.
First, find a PCB fab that will do internal routing 
Best is to just come up with the manufacturing files and e-mail them to their contact person and ask "Can you make this?"
Second, generate a separate routing layer and draw the circle representing where you want routing to occur. Include this with your manufacturing files in RS274-X format. Be very clear (write in text on the layer itself) whether the circle represents the tool path (in which case you have to account for tool diameter, which you should specify) or whether you want this to be a finished boundary.
Third, include a picture/drawing/sketch/rendering of what you want the final product to look like, with dimensions, so there is no confusion!
- How do I create a circular PCB (in EAGLE)?
Just delete the default rectangular outline and draw a circle on the dimension layer (20) to represent the edge of your board.
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons
"Evil Mad Scientist Labs" wrote up some of their experiences creating a clock kit with oddly shaped PCBs: On the design of the Bulbdial Clock | Evil Mad Scientist Laboratories
At work, we use annular* PCBs with additional internal routes all the time. We just show it in the Gerber files the finished dimension as we would any board shape. Since we do this all the time, the board house knows what to do. So, definitely contact your board house and find out what they want to do it. Some will say they don't do that. Just find another board house because it can be done, even routinely.
Language Police:
*Annular is in the shape of an annulus (two concentric circles) as opposed to donut-shaped (a torus).
Thanks guys. If I make a solid disc with large amount of drill holes as shown on the evil mad scientist website, I can get the hole I want and then worry about cosmetics later when I get a working unit.
I've done that before, lots of small holes with no plating, punch it out and spent 10 mins with a half round file to clean up.
Rob
a solid disc with large amount of drill holes
When you get charged for a PCB one of the things determining the cost is the number of drill holes. It might be cheaper to have the PCB manufacturer route out the central hole rather than drilling lots of holes. Ask them.