I have only just started to play with electronics (literally less than a week ago) and have purchased myself some cheap Arduino Nano clones, as well as some LEDs, resistors (only 10 ohms at the moment, but more varieties are coming), a breadboard and some jumper cables.
The reason I've got into this is that I also make scale models and want to light them up with LEDs and fibre optics. I may play with Bluetooth connectivity etc as a later date, but first, my issue with multiple LEDs and their power requirements.
Please excuse and correct me if any of this is wrong, its all based on my current (and probably incorrect) understanding at this point...
The Arduino Nano has 15 digital I/O pins and 6 of them use PWM. These pins output 5 V at a maximum of 40 mA (20 mA is recommended).
I want to run 4 LEDs from one of these pins. The LEDs I have are 3.3 V and 20 mA.
This means that I'll either not be able to light them (9.9 V / 20 mA if I run the LED's in series) or I'll damage the Arduino if I run them in parallel (3.3 V at 60 mA).
I came across a video (Here's the link) that discussed this issue, and suggested the use of a transistor to get around it, and the video makes sense, but it never mentioned how to make sure I get the correct transistor for my project.
Is there a simple way to calculate which transistor I want/need? For instance in my case, I have 4 LEDs, each one needs 3.3 V and 20 mA. What should I look for in a transistor to handle this, and how do I calculate it for myself?