Connect Different Leds

[camilozk]

I am familiar with PWM yes.

thanks for the aclarations on the mosfet.

I only find the IRLD014 in the US and not very cheap (I live in europe), compared with for example the TIP122 that is in use by the tutorial mentioned before. I am very curious why is it that a mosfet is preferred if the TIP122 does the job.

 

[Harald Kapp]

I am very curious why is it that a mosfet is preferred if the TIP122 does the job

The TIP120 is a darlington transistor. In consequence the voltage drop between collector and emitter can never be less than 2V...4V (datasheet) even in full saturation, This voltage drop leads to proportional losses.
A MOSFET, suitably chosen, can have an Rdson in the range of 100mΩ or even much less.
At e.g. 1 A the difference in power dissipation is:
TIP120: 1 A*2 V = 2 W
MOSFET: 1 A²*100 mΩ = 0.1 W
Quite a figure, isn't it?

Google logic gate MOSFET to find parts other than the IRLD014. They are readily available in Europe, too.