Automated Irrigation System

Hello all. I am in the designing stage of building an automated irrigation system for my balcony garden. In my current arrangement, I have four 2'x3' garden boxes, each box with a different type of vegetable growing in it (one box of tomatoes, one of peppers, etc). My intention is to have a piping header with a solenoid operated cutout valve going to each box, attached to a soaker hose in the box, and a separate moisture sensor in each box. If moisture level drops below a preprogrammed level, the pump will turn on and the valve for the box in question will open, allowing the water to flow through the soaker hose until the moisture rises above the cutoff point (valves and pumps are 12VDC, controlled by relays).

My question is this: does anyone that has experience with this type of project have guidance on what the moisture setpoints should be for different plants? Don't want to drown them, but I don't want to starve them either. I know I can experiment with it, but was hoping to not kill the garden in the process of doing so. Thanks for any help you can provide.

I would recomend you jjust get small pumps. and drillper hose.

use a TIP120 transistor or FET. no need for solenoids or relays.

left running, you could fill the cox in a couple hours.

the moisture will spread on it's own in such a small container, but you could put in the hose with holes in it to leak where you want.

Take one of your sensors and make it the master reference.

go into the yard or take a potted plant and let it dry to your touch. then test is and write the 'low' value
then water it a little until you think it is well watered. test it again.

that should be a great starting point.

what the moisture setpoints should be for different plants?

Moisture sensors have a very bad reputation for unreliability. The simple & cheap probes corrode rapidly and fail.

You will probably have to do quite a bit of research and experimentation to find a probe that is reliable and gives repeatable measurements.

There are a couple different types of sensors.
the cheap and dirty ones use resistance. if it is DC only. then you have electrolosys that can effect your sensors.
if you swap polatiry, you reduce that greatly.

there are capacitance types that are entirely encapsulated from the environment. however, your presence effects the reading.....

Interestingly, weight of water and soil would be measurable. at least in a container type system.

Probably you-ll get more precise with adjustable drip heads for each pot and just control the time a single solenoid/pump is wetting all pots