ZAF Plus 16 relay module
The Relays are control 12V lines that are controlled by 5V digital pins from the Arduino Mega. Each relay board controls 15 12V lines that are used to open 15 corresponding valves. We have 30 tanks in our ZAF+ setup, therefore we need two 16 relay modules. Of course, you can scale up your ZAF+ by adding more relays by daisy chaining more arduinos. The main issue with the relays is the large number of connections. As described herein it is just a matter of planning and good wiring and soldering practices. The 16 relay module inputs and outputs are organised with a solder breadboard connected to each valve outside of the electronic box through a screw terminal.
In the following picture and schema, you can see how to connect and organise the wiring of the 16 module relays.
