Project 13: where does power come from?

This is my first visit since 2018, everything has changed - a lot!

I went through the starter kit and all of the projects book in early 2018 then stopped for various reasons a few months later. I am now re-learning by going through each project again and hoping to keep it going this time.

I am up to project 13 (touchy feely lamp) and everything works as expected, but I do not understand how.

I don't think I understand capacitance in general or how my body relates to it and more confusing is where does the power comes from to light the LED, we only have ground from the Arduino to the breadboard?

It must be something basic I just don't get or misunderstand, can anyone help explain please?

Thank you.

Please post the code and schematic of the project

Is this related to that project ?

( pin12 is powering the led which is done in the code by digitalWrite(ledPin, HIGH); )

Thanks @J-M-L , yes that's the one.

OK, I'll take a closer look at the pin specs; I didn't know (or forgot) they can output power; thanks.

They can provide a little current under 5V, the resistor is there to ensure the LED won’t draw too much and damage the pin by requesting more than what it can provide (40mA peak on a UNO, 20mA max usually recommended). 15/20mA is already plenty to light up a basic LED

Perfect thanks @J-M-L ; yep found a good detailed overview of LEDs last time and made some notes (blew a few up of course!).

I'm in the UK so signing off now but can you recommend any resources for learning more about capacitance? Thanks again, I'll check in tomorrow.

Lots of info online, I would start there

And more info here

Fantastic @J-M-L , even the term "capacitive sensing' helped; thanks again, much appreciated.



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