Computing stuff tied to the physical world

The MPS as prototype PCB

Breadboarding is nice and flexible for quick experimentation, but at some point the design starts to settle down and then all of a sudden a breadboarded setup isn’t so convenient any more. Components can loosen, wires can make bad connections, it’s all quite brittle.

With the EAGLE CAD software, which can be downloaded and is free for small projects, and the schematic already set up, it’s fairly easy to create a matching PCB such as this one:

Screen Shot 2015 02 24 at 11 39 31

Most of the effort here goes into placing the parts logically on the board, and then letting EAGLE’s autorouter do the work of finding a way to properly connect everything up.

A few notes about the design process:

  • there’s always a bit of trial-and-error involved in board layout
  • headers and connectors are best placed near the border, of course
  • actual component choices can easily be adjusted, these don’t affect the PCB
  • adding (grounded!) mounting holes make the board more practical and safer
  • the antenna pin of the radio was placed near a corner
  • you have to think about component heights as well
  • this board has no vias and everything except the radio is through-hole
  • this board wasn’t optimised for size but for easy soldering
  • … with lots of empty room around the radio module, for example
  • there’s also a ground plane, covering most of the bottom of the PCB

The end result is a 33×48 mm board, and all it really needs is a connection to the CT on the left, and a pre-programmed LPC810 ┬ÁC inserted in the 8-DIP socket (top right).

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