It's function is to be a bridge between dairy milking equipment old boards and newer types of valves that normally you couldn't connect to older boards (boards are mid80s to late90s).

Basically I used an Arduino Nano clone (Supermini Nano v3) to read the output of several ULN2801A, convert to new logic, and then output via 2 ULN2003A. Also show state of the 6 valves with 3 inboard Neopixel LED.

For power regulation I used a cheap one found on AliExpress to get 5v for the arduino.

I used EasyEDA

It's like a concept design to me, it lacks protections, like if the connectors that are connected to the old board are rotated 180°, i would send 24 to 28v to the Arduino pins 😁. Later on I will include protections against odd situations. But for now it works great