Our ideal solution would have the most accurate sensor, without breaking the bank. This means that we pretty much have to use a capacitance sensor, as we saw earlier in this chapter. These sensors can be obtained as capacitive soil moisture sensors for little more than a few euros or dollars for a simple 555 timer IC-based design such as these:
You would simply stick these into the soil up to the point where the circuitry begins, then connect it with a power source as well as the connection to the analog to digital converter of the MCU.
Most peristaltic pumps one can purchase require 12V. This means that we need to either have a power supply that can provide both 5V and 12V, or use a so-called boost converter to convert the 5V to 12V. Either way, we would also need to have some method to turn the pump on or off. With the boost converter, we can use its enable pin to turn its output on or off using a GPIO pin on our MCU.
For prototyping, we can use one of these common 5V to 12V...