Arduino Fundamentals: Part I: Quiz

Question 24 depends on whether or not you are 'sinking' or 'sourcing' the LED which has been connected...

Question 24 depends on whether or not you are 'sinking' or 'sourcing' the LED which has been connected...

I got that one wrong. I'm of an age where it's more natural to take loads like an LED to the rail: that comes of originally learning logic design with TTL.

I suppose, if you were being strict, you should also set the pin to be an output first.

Jon,

I too started from this perspective and then realised I needed a newer mind set and actually got this question correct.

Dubbie

beacon_dave  wrote:

 

Question 24 depends on whether or not you are 'sinking' or 'sourcing' the LED which has been connected...

True. The question should show how the LED is wired. If it’s between + and pin, the answer is wrong.

On a Nano, the schematic looks like this. I think the question might be about the on-board LED.

In that schematic the LED would only light up very dim (if at all). The 1K resistor should be more like 150R

There are a lot of LEDs these days that shine bright with 2 mA 

It's the LED marked 'L' on the board. It's not all that bright, but it's fine as an indicator on a board. I suppose that they didn't want to load the output pin too much: this way the output pin can be used for other things too.

Point taken.

Maybe I'm just an old man, from a time where diode where leaded and drew 20 mA.

In any case, asking what an LED does, when connected to GPIO pin, that are driven low.

Ranges from nothing at all to damage the microcontroller (I'm talking microcontrollers in general here, not just microchip AVR controllers)