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Sort of off topic but.....Why do LEDs smell so bad when they frie?
Light emitting diodes (LEDs) are bits of silicon that light up when current flows through them. Go google for the science. As a general rule of thumb, LEDs can have 20mA max current flowing through them before they begin to fail.So if you hooked up your LED like in the above schematic, it would light up very bright for a split second and then burn out. That's cause the LED is a diode and the current will flow from the anode (arrow) to the cathode (line) to ground - uncontrolled! The silicon will flow current at something like amp for a split second and burn up. To limit this current flow to 20mA, we need Ohm's law. Yea, the book worms in the room suddenly perked up:V = IR (this is Ohm's law)If we have 5V, and we only want 20mA flowing through the LED:5V = 0.02 * RR = 250 OhmNow this is not completely true because the LED has a forward voltage drop, but don't worry too much about that. Hooking up LEDs is very common with micros. All you need to remember is that you're going to need to limit the current. The most basic way to do this is with a resistor. 220 Ohms will work (LED will be brighter), 330Ohm is also good (LED a bit dimmer), 1K (1000) will work as well. 220, 330, and 1K are more common resistor values.I highly recommend you get your hands dirty. Hook up an LED to a 1k resistor, then a 330, then a 220, 100, 50, then finally blow the thing up by hooking it with no resistor. That was fun right? Good. You had a back-up right? Once the bit of silicon inside the LED is burned out, it is no good and the LED can be thrown away.
After about 3 hours in total of use the LED fried
Here's an equation for calculating the value of the current limiting resistor when you use an LED:Resistor value (in ohms) = (Supply voltage - LED drop voltage) / 20 mA