Cool. So you're needing current limiting resistors.We are going to be using jumper wires and breadboards to build simple circuits with LEDs and such.
Short answer, obfuscates a lot: use a 220 ohm resistor in series with a red LED. It's maybe quite a large value so it won't make for the brightest LED, but it's what gpiozero used. (Or is that a 330 ohm? That might work too)
Longer answer: LEDs don't last very long if they get too much current. Every colour of LED needs a particular minimum voltage to light it. The oldest LEDs (red) need the lowest voltage, and the newest technology (blue and white) need the highest voltage. Without a current limiting resistor, a red LED will burn brightly but not for very long.
If you want to work out a very precise current-limiting resistor value to get the brightest possible LED, this is handy: LED Dropping Resistor Calculator. The Supply voltage is 3.3 V, and you probably want a current limit of no more than 20 mA. For the voltage drop across the LED, use something like 1.7 V for red, 1.9 for yellow and green, and 2.6 for blue and white.
If you have LEDs to spare, maybe deliberately fry one with a 9 V battery. The bright flash and resulting smell of "magic smoke"* is memorable.
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*: the thinking goes like this - once the smoke comes out, the thing doesn't work. So it must be the magic smoke kept inside the LED that makes it work. Yes, that definition would make Nakamura Shūji (inventor of the blue LED) cry because there's some difficult physics that is behind why LEDs work.
Statistics: Posted by scruss — Sun Mar 24, 2024 10:21 pm
