I haven't posted a schematic yet, sorry. However, there is literally nothing to do except connect the Arduino to the LCD and Keypad according to the pin-definitions in the source file. I will get around to drawing one soon that shows how to interface a solid-state or coil relay.

PS: new code is uploaded, it now does test-strip (differential exposures for each step) and test-tile (complete exposures for each step) generation. Always 8 steps, but you get to choose the base exposure and difference in stops between steps. Test strips are the classic approach we all know and test-tiles are how I prefer to do exposure testing. Tiles take a little longer to expose but you get the same part of the image visible in each step of the test so you can pinpoint exactly the exposure you need for a particular highlight or shadow for example.

You'll probably have to shift-reload the webpage, which now has some "WTF is an F/Stop timer" explanation and a link to a Gene Nocon interview.