Here’s a photo of a finished RPi-X PIAC experimenter module:
PIAC = Pi Industrial Automotive Controller
It’s a Pi expansion shield that has 4x Change Over (CO) relays, 4x Opto Isolated Digital inputs and 4x 0V to 10V Analogue Inputs. There’s also a RS485 interface to communicate with industrial networks.
You can use it to learn about industrial control or perhaps even use it on your own small control projects.
I hope to have it stocked in our Tindie store soon: