Automatic home plants watering system (under $10 bucks!) - Arduino Nano v1

This is an under $10 home plants watering system.
It consists on measuring the humidity of soil, deciding when it´s dry enough, then turning on a water pump (a solenoid can be used if you have a hose around, I hadn’t, so I used a 5 liters “bucket”).
It´s my first time coding and using the Arduino, so don’t expect a beautiful code...
No soldering is needed. This could be a plus for some people, but made the control box a lot bigger. I’ve tried to do a smaller version, but hadn’t enough space for the wires.

Parts needed:
10 x M3 nuts
1 Arduino Nano ($2.79)
https://www.aliexpress.com/item/Nano-CH340-ATmega328P-MicroUSB-Compatible-for-Arduino-Nano-V3/32572612009.html

1 Step Down power supply ($1.09)
https://www.aliexpress.com/item/Free-shipping-1pcs-XL4005-DSN5000-Beyond-LM2596-DC-DC-adjustable-step-down-5A-power-Supply-module/32730909898.html

1 Relay module ($0.65)
https://www.aliexpress.com/item/KY-019-5V-One-1-Channel-Relay-Module-Board-Shield-For-PIC-AVR-DSP-ARM-for/32358134833.html

1 Humidity sensor module ($0.58)
https://www.aliexpress.com/item/Smart-Electronics-Soil-Moisture-Hygrometer-Detection-Humidity-Sensor-Module-For-arduino-Development-Board-DIY-Robot-Smart/32562744759.html

1 Mini Protoboard ($1.98 5 pieces)
https://www.aliexpress.com/item/5PCS-SYB-170-5-Colors-Mini-Solderless-Breadboard-Prototype-Experiment-Test-Protoboard-170-Tie-Points-For/32671297865.html

1 Arduino male jumper wires ($1.00)
https://www.aliexpress.com/item/40PCS-20cm-male-to-male-2-54MM-1P-1P-Dupont-cables/32648521256.html

1 Arduino female jumper wires ($0.67)
https://www.aliexpress.com/item/Dupont-line-20pcs-10cm-2-54mm-1p-1p-Pin-Female-to-Female-Color-Breadboard-Cable-Jump/32846005876.html

You will also need to print this cover for the sensor:
https://www.thingiverse.com/thing:2474432
(I couldn’t use bolts, had to hot glue)

The last thing is find a 12v DC power supply of at least 2A. I had an old printer power supply laying around, so I used it. 2 Amps is barely the minimum. I tried a 1A but when the pump was turned on, the voltage drop was significant high to reboot the Arduino.
Optional print/buy:
Water pump support, made for mounting on a 35mm plastic “pillar”. (STL had to be fixed, I had a problem exporting in Solidworks)
This is the pump that I used:
https://produto.mercadolivre.com.br/MLB-779586151-bomba-reservatorio-agua-limpador-do-parabrisa-universal-_JM

I could not find it on Aliexpress. It costed me $3.00
The pump that I used is very similar to the one below. It wont fit the STL file, but the support that I used is for a very particular case, so I think it has to be done again…
https://www.aliexpress.com/item/New-Black-Windshield-Washer-Pump-For-BMW-E46-E38-E39-E60-E65-X3-E53-X5-Z4/32807872201.html

After print everything, I had to cut the wires of the 12v power supply and use the male jump wire to connect it into the protoboard.

Then connected into the DC-DC Stepdown power supply and adjusted it to 5v. Then used the male jump wires to connect it into another line of the protoboard.
Used a male and a female jumpwire to directly power the Arduino Nano, plus the VCC of the Relay board. Do not connect the humidity sensor directly on the 5VCC, since I read that many sensors suffer from premature wear when its always powered on. I used the digital IO from the Arduino to power it.

There is an plastic “pin” on the case. This is used to fasten the pump and power supply wires with hallermann ties.

The idea is to turn on the sensor using digital IO, then measure humidity using an analog input. If the humidity is greater than 650, the soil is very dry. Another digital IO makes the Relay board give 12v to the pump. Then it compares if the humidity has changed at least 10%, and tries 20 times to make the soil reaches 400 units of humidity. If it fails, maybe the water has run out or any problem with the pump, then the programs goes into an infinite delay.

The sensor must the somewhat close to the water hose exit. I´ve used some delay to give time to the water penetrate into the soil and reach the sensor. Lower delay times between “pump and measure” gave me very wet spots. That’s why the there is almost 10 seconds between cycles.

Pump must be "submerged", so it must be placed under the water vase to be always wet.

I´ve been using this for over a month. It uses 5L of water for 1,5 week. It´s a big vase of 80x40x15 cm.

PS: This is a 2018 project that has been taken down by Thiingverse without any reason. This is just a re-upload!