Sensors and Controls
The moisture sensor that is used is a generic 5V sensor that can be run either as an analog out or a digital out. The digital out gives you an adjustable trim pot that runs into a comparator. We will be using the analog out which gives a voltage out between 0~4.3V. This analog out will be run into the analog to digital convertor in the microcontroller to give a more accurate reading of the moisture level.
The control to the LED arrays and the water pumps is done by FQP30N06L MOSFETs. These MOSFETs were chosen because their turn on voltage allows them to be turned on from the microcontroller without the need for an additional op-amp.
The microcontroller can only output roughly 3V and we want to make sure that the MOSFET is fully on at that point. Looking at the datasheet it turns on between 1~2.5V so it should be fully on at 3V.
The KL25Z is a microcontroller made by Freescale. It impliments an ARM processor with many choices all the pins that it has. It will be running at 48MHz in this system. There will be 3 GPIO pins set to output to the three water pumps. There will also be 2 GPIO set to output to the two LED arrays. Finally there will be 9 pins set to ADC convertors for gathering information from the moisture sensors.