This is a basic watering system I put together to keep my giant atlantic pumpkin hydrated while I was working away. Only cost a few dollars and about 20 minutes to put it together. The watering lines have since been added to to water my other garden beds.
This is an overview of what I have done rather than a step by step of how to make it, I wanted to make sure it worked before I made an instructional incase it didn't work.
Step 1: How It Is Put It Together
-small solar panel
-old car battery
-wire and a diode
-cheap electronic timer module from online (only a few dollars)
-some sort of sealant for the plastic container
-silicone or sikaflex will do
-assorted watering system pipe fittings depending on how your system is set up
There is no reason why you couldn't use multiple timers and have more solenoids to control other sectors independently.