Traditional rectilinear grids become an issue when you have to design a round PCB, including placing components and routing tracks in circles!
Yesterday, the illustrious Max the Magnificent sent me an email asking whether I knew of any PCB design tools that would allow objects -- like LEDs or other components -- to be placed in a radial fashion.
This is a good question. If you stop and think about it, PCB designers have been using the concept of a grid for decades and we tend to like everything in neat and tidy rows and columns. Maybe it’s because of our love for matrices and linear algebra? I don’t know, but -- for whatever reason -- everyone’s concept of rectilinear grids becomes an issue when you have to design a round PCB, including placing components and routing tracks in circles!
Now, I honestly do not know if there are any other PCB design tools that can do this -- I’ve yet to see one -- but I do know that radial grids are allowed in Altium Designer. In fact, users can set up a number of different grids and have them overlaid and in effect for either components or other items to be placed.
Here is a little hobby project I was working on when the advanced grid features were being added to Altium Designer version 10. It’s a PCB for a stroboscopic guitar tuner.
I wanted an ARM7 microcontroller in the center of the board, mounted at 45°, so I made the center of the board the origin and added a rectangular grid with a 45° rotation. In other words, a rectangular grid doesn’t have to be parallel to the X-Y axes.
Just outside this you can see the polar grid, which I used for the LEDs. This allowed me to place the LEDs in a perfectly spaced circle.
The grids were configured with an order of priority such that the default snap grid sits behind the tilted grid in the center, which is itself behind the polar grid that's used for LED placement.
What this basically means is that -- when I’m placing parts -- the mouse cursor snaps to whatever grid it’s currently hovering over. This makes it much easier and faster to do this kind of design.
If you think about it, we’re so accustomed to using the word “grid” -- and to visualizing this as being presented in a "North-South, East-West" fashion -- because it’s what we've grown to expect to see on the screen of whatever CAD package we happen to be using. I grew up doing mathematics in a “grid” book. Also, working with gridded paper made it easy to hand-draw neat and tidy schematics when I first started learning electronics. In the case of modern tools, however, it’s not really a grid -- instead, what we are really doing is controlling where the mouse cursor snaps to. Can you imagine if the tracks on your PCB really did have to stay on grid in their entirety? That would be untenable!
So, in essence, I think we’re better off calling this sort of capability something like “snap management.” But whatever we call it, it really does help being able to put those LEDs in a perfect circle! Here’s the 3D view of the board I was working on:
The LEDs I chose were blue OSRAM TOPLED reverse-gullwing types, the idea being that the LED aims the light out through the backside of the PCB where there would be a Plexiglas panel. Cool huh? Maybe Max would like to use this method for the dials on his Inamorata Prognostication Engine?