circuit explanation (Solenoid and sprinkler)

In this DICM circuit, the solenoid and sprinkler motor as known as output are used to fertilizer and pesticide the crops automatically. The connection of this output will be shown in the picture below.

Referring to the connection above, the output of this DICM system is actually controlled by using the TIP 120 and this TIP 120 as a power transistor. Picture below shown the connection of TIP 120 to the output. 

Referring to the picture above, the digital output signal from the Atmega 328 will be sending to the base of the TIP 120. When the output is high (1) current will flows from base (B) to Emitter (E), the electronic "switch" is closed and current flows from collector (C) to emitter (E) and the output will be active or turn on. The turning on of this output will active the solenoid and sprinkler motor to perform their functions to fertilizer and pesticide the crops. Picture below shown the connection of TIP 120 due to output which are solenoid motor and sprinkler motor.