Sure thing, let’s get the numbers straight. What’s the layout like and how many zones are you planning?

Looks solid. Four equal zones keep the layout symmetric, which is easier to balance. For the drip lines, aim for a flow rate of about 2 litres per hour per plant, so you’ll need a small pump per zone that can be controlled by a flow‑rate sensor. The hydroponic stack can use a recirculating nutrient solution; just keep the pH steady at 5.8 to 6.2 and the EC around 1.5 dS/m. For the compost bin, keep it on a separate drip line so you can use the liquid as a nutrient mix for the tomatoes. Finally, make sure the rain‑water catchment has a first‑flush diverter so the initial runoff doesn’t bring in debris. With a programmable timer, you’ll get consistency without fuss. Any particular part you want to dive deeper into?

Use a low‑cost ultrasonic flow sensor like the YF‑S201 or a more accurate magnetic encoder such as the DPS‑02. The YF‑S201 will keep the budget low and gives about 0.1 L/min accuracy, good for a drip line. If you want tighter control, go for the DPS‑02; it’s only a bit pricier but gives ±1 % accuracy. For the timer, tie the pump to a simple PLC or a microcontroller with a rain‑water level sensor. Put a float or a resistive level sensor in the catchment tank, and program the controller to wait until the tank reaches, say, 80 % capacity before triggering the irrigation cycle. That way the system runs only when there’s enough water, and you can adjust the delay if you need to conserve rain water during a dry spell. Make sure the timer can also skip a cycle if the level is too low, so you never pull a dry line.