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I am building a system to automate a vertical farm (specifically watering, lighting, and drying) and am having trouble choosing between a wired or wireless system architecture.

The farm is arranged into a vertical matrix of 'trays' (like drawers in a large cabinet - each tray has one specific type of crop) that is currently ~7x7. Each tray must be independently controlled.

Each tray will need two relays for two solenoid valves (source and drain) and feedback from a float switch for watering, plus an additional two relays for lighting and drying control - meaning 4 digital outputs and one digital input per tray.

The entire system will be controlled form a central computer. For the current farm this would entail 196 outputs and 49 inputs, but I want to design this system such that it can be scaled to any size.

So these are my questions:

For a wired network,

-Can I chain together a (theoretically) infinite number of shift registers to give me the required number of digital outputs to control these simple devises?

-Is there something similar to a shift register that can manage a large number of digital inputs and reduce the number of pins required on the computer board?

In General,

-Between a wired architecture (using something like an Arduino/raspberry pi with shift registers) and a wireless one (using something like a Zigbee mesh network to manage all the devises), will they both have similar reliability?

Thanks in advance!

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  • \$\begingroup\$ Check out pre-assembled DS2413 based PIO boards. They are cheap, with two I/Os. You can put hundreds of them on a Onewire bus, they all have a factory-set individual address. Drivers for the Arduino and Linux are available. \$\endgroup\$ – Janka Dec 1 '18 at 22:40
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If this is for a commercial project then go for industrial hardware.

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Figure 1. 16 Channel Digital Input with Pulse Counting RS485 Modbus Slave. Source: Audon.

Figure 1 shows a randomly chosen RS485 remote I/O module. These are usually 24 V powered and can feature screw terminals, input and output isolation, etc. The RS485 network will give noise immunity, etc., each station will have its own address and the rest of the system will work if that node drops off the network.

One of the big benefits of using commercial hardware is that there is support and someone else will be able to repair it.

You can still have all the fun of creating the HMI and control software on the hardware of your choice - but a PLC (programmable logic controller) would be the standard approach for industry.

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