question?

In this project circuit http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads How many stage does this project has? I need this for my capstone project?

It has five main stages but stage 3 has sub-stages 1 and 2 so you might see it as 6 or 7.

johnwasser: It has five main stages but stage 3 has sub-stages 1 and 2 so you might see it as 6 or 7.

Can you tell me these stages?

Im kinda new to this world of electronic but i know that the output voltage is 3.3 or 5V, so the first stage is a TIP-120 transistor to feed the Arduino Uno microcontroller with the required 5v needed for its operation.

The Arduino does not get 5V power from the TIP-120 transistor.

There are four ways to provide power to the Arduino:
USB cable provides 5V 500mA.
Built-in regulator can accept 7V to 12V and provide 5V 1A.
There are two ways to feed the built-in regulator:
The power jack (center + and sleeve -)
The Vin pin (+) and Ground (-).
You can use an external regulator and provide regulated 5V to the 5V pin (+) and Ground (-).

The transistor acts as a switch: http://www.electronics-tutorials.ws/transistor/tran_4.html

The Arduino can use a weak (40 mA max) 5V output connected to the Base of the transistor to switch a higher current and higher voltage.