Need advice on DigitalOutput


I’m playing around with FEZ Spider and a BreakoutTB10 module. As I’m a beginner, that question may be completely stupid, I know I’ll have to read about basic concepts of electronic devices but I want to do it along the way.
I connected an led to the first pin (+3.3V) of my breakout module and get what I want: my led shining bright. If I connect it to another pin I’m setting with

it turns on, but is very... dark. Please tell me why this isn't as bright as when connecting to the +3.3V pin directly. That was what I expected after reading this in the documentation:
[quote]If the processor is powered off of 3.3 V, then the state high means that there is 3.3 V on the output pin. It is not going to be exactly 3.3 V but very close. When the pin is set to low then it is voltage is very close to zero volts.[/quote]
Using another socket or an additional power source didn't change anything.

@ MrBlinky - sounds like the led you are using requires more power than what can be provided by an io pin. the 3.3v source is able to provide the required power.

The product page of the led says “Max power 5mW”. Is that too much? I just wanted to blink an led and didn’t think that would need so much power :smiley: Sounds like I really have to get some basic skills before I can do more… complex things :smiley:

LEDs aren’t necessarily simple :slight_smile:

LEDs consume current, in amperes (usually measured in milliamperes). Watts isn’t an effective measure of how much current they draw, because it’s a function of power, meaning current * voltage. LEDs also do vary what the forward voltage (required voltage to drive the LED on) is, so it’s never as simple as saying 3.3v * X milliamps (although it’s an ok approximation)

Anyway, you do know you should also be using a resistor with an LED right ? This is actually designed to reduce the current flow through the resistor, to both protect the resistor and the IO pin. You don’t want to burn either of those out (although realistically, the LED is easy to replace right :slight_smile: ). If you already have a resistor in place, then you could optimize the brightness by using a smaller resistor, but again there’s that tradeoff and increased risk of damage…

And yes, welcome to the wonderful learning playground :slight_smile: If you want to learn about methods for higher current IO switching and perhaps running multiple LEDs to increase brightness, you’re going to need to learn about transistors (and many other things :slight_smile: )

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