This is an easy tutorial showing how you can control the brightness of an LED or adjust the speed of a DC fan using Arduino Board, a small BC547 transistor and a potentiometer ... Dot not forget that ...

If we asked you to light up an LED ... an Arduino, there’s a good chance you’d know exactly how to do that. How about a bunch of LEDs? Simple. Now turn on LEDs proportional to an input voltage.

This variable resistor is connected in a voltage divider configuration, and Arduino collects a voltage ... the desired moisture when to light up the LED and signal that the plant needs water. Adjust ...

[Jakub] found himself in need of an electronic load, and instead of a transistor and a pot ... voltage. Control everything with a DAC, and you have a programmable load controlled by an Arduino.