This is the easiest and cheap plant watering system you can make.i didn't use any microcontroller.it is basically a transistor switch.you need to add some resistance between collector and base, to prevent transistor from getting defacted.(dont use without resistance if you do you will witness holly smoke) you can watch video HERE. and you can directly SUBSCRIBE MY CHANNEL CLICK HERE
Step 1: Parts You Need
1. Pcb - 1
2. Transistor - 1 (bc 547)
3. Vr - 1 (1-2m ohm)
4. Resistor - 1 (1k)
5. Relay switch - (6v)
6. Metal probes
Take a pcb and fix and solder all components according to schematic.
This is the circuit diagram.as i told yoh this is a transistor switch.
Before connecting pump make sure circuit is working properly. For that i have connected an led with battery. After testing it will replace led and battery with pump.
Now after that testing i connected a small water pump.whenever soil gets dry,the resistance between two probes increases that makes pump on.after soil gets water the resistance between two probes gets low that makes pump off.