I'm an engineer and a farmer.
I'm working one a chip opensource solution for irrigation control valve.
My specifications :
Use latching valve.
Long range remote control ( 500m with some tree)
4 month automy
Under 50 euro per unit
My complete design will be :
A remote center, based around an arduino pro mini with 4g module and an RF Module
This base will receive my order from my phone (using a web server) and send it to slave control valve using RF Module.
I'm currently working on the PCB of the slave Valve.
But i need some help to check if the solution used is valid.
You will find all my work on git hub. (Search for Slave_Valve.pdf to get the schema)
To control a latching solenoid we need a circuit able to create a 100 ms 12v impulse through a 6 ohm solenoid.
On my schematic I create a step up module around a ADP1108.
I use a capacitor (C2) to store enough energy.
A Mosfet (controlled by an Arduino) and a 2 pole bistable relay are used to discharge this capacitor and switch the polarity if needed.
Do you see any problems on this PCB?
If the working principle is good I will calculate all the value of the components.
Why are your slave devices using a low voltage battery that has to be manually recharged every 4 months?
Outdoor systems typically use a 12v battery charged by solar or wind for unlimited power. If you are going for really cheap then try connecting to the battery inside a solar powered garden light. You could run several in series to get whatever voltage you need.
Have you checked to see if the Nano works with 3.3v going into Vin? That is well below the specified input voltage.
Also the Nano has a high power consumption in sleep mode due to the serial interface chip etc.
If your Nano has a 16 MHz crystal then 3.3v is too low for reliable operation.
I am not familiar with the relay you used but normally you cannot drive relays with micro pins. The voltage that develops when you shut it off will eventually destroy the arduino. If you are using a lithium battery you are asking for problems there is no control for it. Have you looked at one of the ESP devices, you can get by with a lot less current without modifying the unit. I am having a hard time with this system and will see if I can find this again. The excess amount of white space they use is ridiculous. When you get the values in it will help.
Please try and not use an off forum source for your data.
Can you post here a jpg or pdf of your circuit, not a .sch as not everybody has Eagle.
Also jpg images of your PCB.
They are called BMS or battery management systems. They come in different cell counts and control and balance the batteries. They can be gotten for less then a Buck from your favorite china supplier. Simple rule if you use Vin you lose about .7 volts because of the protection diode. There are some boards that use a FET which will be less then 0.1 volt drop. Look at LoRa it sounds like it would be a good fit for you. This link has some info: ESP32 with LoRa using Arduino IDE | Random Nerd Tutorials
I don't think i need BMS (i use one cell so no balance problem). On my schematic, I add an FS312 it's an overcharge/discharge,short cut IC. Furthermore I will charge the cells by an external charger.
