A quick video update: https://youtu.be/vnUFV_amSPQ
The tomatos and peas are trying to go through the roof. Cucumbers are close to follow. They are all aiming for the ventilation hatches - I think they are planning a grand escape...

The NFT system pump stopped working coupe weeks after setting it up. Have not gotten around to ordering a new pump. That will be a project for next year.

As you will be wanting to receive the information and perform actions in the vicinity of the GW, I would go with a RPi + NodeRed + NRF24. Then switch the Raspi into Access Point mode and you'll be able to hook your phone up to it to receive notifications and control settings.
For a GSM connection, either add a USB modem or a GSM module to the IO pins, then connect to a MQTT broker on a VPS

That way you will only need to supply power to the Raspi and you're done.

Confirmed. Removing the jumper and using a power supply separate from the arduino’s has cured it from reboot issues.

Awesome work! I was trying to create a bridge between a MQTT gateway and a Serial gateway (over TCP) so I could use firmware upload function of the MySController. However for some reason it seems to only work one way. I can send commands from the MySController to MQTTGateway but nothing is being received on the MySController side when data is sent from MQTT

This is my flow, would be awesome if someone would spot the issue...

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Disconnecting the load eliminates the issue flat out.

I think your previous question just triggered a lightbulb. While the module does have optocouplers in place, I have the VCC bridging jumper in place. So essentially Arduino is still sharing the power with relay coils. I'll install a step-down to get a 5V line from the pump power supply and use that to drive the relays. I believe that should eliminate my reboot issues.

Yes, the relay module has optocouplers separating data lines from the relays.

A long overdue update.

In the end I basically ended up using a GSM gateway with a LCD and couple sensors (air temperature and air humidity) and two relays. The relays control my Dutch bucket system pump and ventilation fans.

As a separate sensor I'm using a Z-Wave multisensor to keep track of nursery temperatures and lux levels.

The pH meter module did arrive but I do not feel comfortable keeping it submerged in the nutrient solution at all times so I've been just taking a sample of the nutrient solution from the tank after mixing a new batch, and testing it indoors, at the computer.

As for the EC meter, I failed to get any of the "arduino only" examples to produce reliable readings. So I've ordered 5 PCB's for this thing: https://www.sparkyswidgets.com/portfolio-item/miniec-i2c-ec-interface/
Once they arrive, I'll see if I can get more reliable results with a separate module.

So far the whole thing has been running almost perfectly. The only drawback is an occasional reboot of the gateway when switching off the Dutch bucket system pump. I'm using two separate power sources for Arduino and the pump, Added a 1000uF cap to the Arduino power rail and a flyback diode across the pumps power lines. Still getting that reboot about 50% of the time.

Some pics to wrap up my rant.
PS. Yes, that's a webcam in my greenhouse. It's taking hourly snapshots for a timelapse

My NFT rails for herbs. A good eye can spot some dill, basil and cilantro plants in there.

That's my "Nursery" - an old fish tank I can cover with a piece of glass when night temps dip below 10C

That's my Fibaro Motion sensor. An easy way to get some essential readings. Like the length of day, hours of sunlight, temperature.

This is my ratsnest. I should have moved the relays to a separate enclosure further away. Right now I think the arc when breaking contact is what's causing an EMP pulse and rebooting my Mega.

Ventilation fans. The temps soared to high 40's and low 50's with door and both ceiling hatches wide open. The fans kick in when air temp reaches 25C

Got some work done on the hardware side of things. Drainage is done, next up is feed part.

Built half of my dutch bucket system. Namely the drain part. Irrigation to follow.

According to thethingsnetwork.org map, the closest lora gateway is about 120km from me