Sounds like a great idea – a little plant therapist with a blinking mood light. Start with a cheap capacitive soil‑moisture sensor; wire two flat‑blade probes into the soil, connect one to 5 V and the other to the analog input through a 10 kΩ pull‑down. The sensor’s resistance drops when wet, so your ADC will see a higher voltage. Add a 0.1 µF ceramic cap across the probe pair to smooth out those quick spikes from raindrop‑like moisture changes – I hate those little surges that fry a board. For the watering control, use a NPN transistor (2N2222 or similar) with a 1 kΩ base resistor. Drive the base from a digital pin that toggles when the moisture voltage falls below your threshold. The collector goes to the relay or MOSFET that powers a small water pump or solenoid valve. Keep the pump supply isolated with a diode across the coil; the diode’s cathode to 5 V, anode to the transistor side – prevents nasty reverse currents that could turn the LED flicker into a fire alarm. Now the LED status light: a 3 mm green LED with a 220 Ω series resistor on the same digital pin you’re already toggling. Tie the LED to the transistor collector so it only glows when the pump is on. If you want a gentle blink when the plant is “well‑watered”, flip that pin high for half a second, low for half a second, and repeat. Use a 2 kΩ pull‑up on that pin so the MCU can read it again if you want to log status. Cable management: braid a few 22 AWG wires, label them with masking tape, and stack them in a zip‑lock bag. The probes can be tucked into the pot’s bottom with a little foam. Keep the relay board and pump on a small breadboard that sits behind the plant so nobody trips over a stray lead. If you want to hide the wiring completely, use a 3‑D printed pot cover with holes for the probes – that way the plant looks neat and your breadboard remains a battlefield only you know about. And remember: a resistor‑hoarder’s secret rule – keep spare 10 kΩ, 1 kΩ, and 220 Ω handy. They’ll save you from a midnight “where did that 220 Ω go?” panic. Happy tinkering, and may your plants never complain about their water supply!

Nice, thanks for the offer. I’ll sketch the layout myself – that way the breadboard can still double as a battleground for future experiments. For the pump, a 5 V 200 mA DC mini‑pump should be plenty for a small pot, but keep the tubing short to avoid a vacuum trap. If you need the exact dimensions, just ping me – I’ll send you a list of the parts and a quick diagram in plain text. And remember, if the LED starts flickering like a dying heart, it’s probably a bad connection, not a mood problem. Keep the cables tidy, and let the circuits breathe.