Need some pointers on my automated hydroponic nutrient reservoir

Other Hardware General Electronics
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Hi all. Excuse my ignorance of electronics. I'm a total newbie and have been going round and round researching all sorts of material and would like a little assistance in understanding if I'm on the right track, or barking up the wrong tree.

I am attempting to create a nutrient reservoir for my hydroponics setup that will use sensors to monitor the volume (either submersible pressure sensor HX711 200kg, float valve, or combination), topping up as required from a freshwater reservoir. It will also monitor the composition of the nutrient solution (pH / EC / temperature sensors) and adjust when necessary. I'll look to ensure freshwater isn't supplied when low weight / low pressure sensor reading during flood cycle.

I have a 12V DC 10A power supply. I intend to remove the connector to reveal the wires and split the + and - for use in multiple relays. From what I understand, the cleanest way is to use one of these - 12 Terminal Power Distribution Block Bus Bar,48V 180Amps Rating Marine Bus Bar, Automotive and Solar Wiring - Battery Terminal Distribution Block,Equipped with 32PCS Ring Terminals,（Pair, Red & Black） : Amazon.co.uk: Business, Industry & Science - connecting the positive to one, and negative to another, splitting into many outputs / sharing ground from a single +/- input.

The things that will be running constantly I will put on another PSU, such as the sensors and the HX711 / submersible pressure sensor. That's another post I guess.

The pumps / relays I have are -

Flood, Freshwater top-up, Sensor tank =
Tyenaza Submersible Water Pump, 800L/h DC 12V 18W 5m Brushless Submersible Pump Mini Silent Brushless Motor for Pond Fountain Pool Aquarium Water Circulation System : Amazon.co.uk: Garden - 12v DC 18W 1.5A Brushless Submersible Pump (x3) - These will sit in my reservoir and will flood my tray above
[Amazon link removed] - SunFounder 4 Channel 5V Relay Module 28VDC 10A
2pcs DC 12V 4.8W Mini Brushless Submersible Pump Water Pump Centrifugal Pump 240L/H Aquarium Garden Fall Fish Container Water Fountain Entertainment Nozzle Diameter 8 mm for Pool Aquarium Fish Tank : Amazon.co.uk: Garden - 12v DC 4.8W 0.4A Mini Brushless Submersible Pump (x1) supplying mixing tank housing sensors within nutrient reservoir.

Nutrient dosing -

IRF520 MOSFET Driver Module MOSFET Button Drive for Arduino MCU ARM Raspberry PI 5pcs : Amazon.co.uk: Business, Industry & Science - IRF520 MOSFET Driver Button Module (x7)
[Amazon link removed - Small peristaltic Pump 12V dc Motor Kamoer KPHM100 Long Service Life high-Precision Liquid dosing Pump 100ml/min]
I understand I need a diode between the terminals, I don't know how to select the right one or how I would install it either. Advice would be greatly appreciated.

Arduino Mega 2560

Apologies for the wall of text. Wanted to provide as much info as possible.

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Wrong choice; that is not a logic level MOSFET. Find one that has a L in the name (IRL...) or others (like FQP30N06L, might be obsolete).
An IRF520 can work but you will need an additional driver (e.g. transistor) between the Arduino and the gate of the IRF520).

Any 1N400x (e.g. 1N4007) will do as far as I can know. You can look at the schematic at Gammon Forum : Electronics : Microprocessors : Driving motors, lights, etc. from an Arduino output pin.

I don't have enough knowledge of electronics to comment further.

1 Like
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It looks like you have a good start. The next thing before purchasing product is to draw an annotated schematic showing exactly how you will connect all of this together. Do not worry about mistooks we will help you through it.

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You have a lot of monitoring and stuff going on, but who monitors the monitoring? Does your hydroponics only operate when someone is present to ensure all is working properly? How long do you envision power failures for your operation? We have had 11 hours when a transformer in a substation shorted. Are you going to maintain temperatures and do something if out of bounds?

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Sob story incoming...
I'm full-time carer for elderly parents with inadequate financial support. I'm hoping this setup will allow me to be 180miles away for a week at a time. I can spend a day per week there for maintenance.

My region is stable power, no reported outages over last 6 months (records only exist for outages >3minutes). I was thinking an emergency power to my arduino with battery should suffice during any downtime, just to keep code from resetting (RTC module / pump schedule / tare weight on HX711 in particular).

No air conditioner for the hotter months unfortunately, but the room will be well ventilated with fans.

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Yes, monitoring the monitors.

I spent many paid hours in employment installing and maintaining monitoring equipment on waste water treatment works.

Typically monitoring turbidity, ammonia (pH electrode modified for gas phase), temperature and conductivity.

All very easy if you have the time to look after it all. There's calibration, cleaning for starters. My aim was for it to run at least two weeks unattended. When I say it, there were nearer a 100 installations.

Power wasn't a great problem, but making sure it was still sampling water and not air, was. That's where conductivity came in.

Fortunately, the sites were on part of a large SCADA system.

This was in the 1990's. PLCs yes, no communication other than a 2.4-kb duplex modem.

How much easier it would have been now.

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Beware of algae growth!