[Andrew Sowa] wanted to use an off-the-shelf relay board from Numato Labs. The board lacks a suitable computer interface, which meant that [Andrew] would have to build one, and its input connectors are screw terminals, which meant a lot of wiring. Undeterred, he created an i2c expansion board using an MCP23017 I/O port expander, and with a novel card-edge designed to mate with the screw terminals, solving both problems at once.
The board was designed in KiCad, if you are interested in creating one yourself its files are in his GitHub repository and his board is even available as a shared project from OSH Park. We’d expect the ENIG finish to be an asset with those screw terminal connectors.
The unusual profile of [Andrew]’s board mates just right with the screw terminals, without adding any connectors or wiring to his bill of materials. Of course there is a trade-off between the cost of that extra PCB surface area and that of the wiring, but we can see the wiring getting out of control for someone like him with a reasonable number of relay boards to control.
We’ve featured PCB manufacture in all its facets here at Hackaday over the years. But it’s surprising how often the board is merely the substrate for the circuit. It’s worthwhile to be reminded once in a while that it too is a component, and unlike most others it is one you can endow with the features of your choice rather than having to rely on what can be found off-the-shelf.