What You'll Need
- LEDs - Various Colors
- 1k ohm resistors - one for each LED
- Soldering Iron
- Wire Cutters
- Take one of leads of a 1k ohm resistor and wrap it around one of the LED leads a half inch down from the LED - I always put the resistor on the anode of the LED (the longer lead), but the important thing is to be consistent.
- Solder the two leads together.
- Cut away the excess leads.
As long as you are consistent as to which lead you solder to (anode or cathode) you will always instantly know which LED lead needs to go to power and which goes to ground.
Another thing you can do with these is add female crimp headers to the lead ends so they can be used on the male header pins of development boards! I make a few with and without.
Any color LED will work just fine, but red is the best because red LEDs typically have the lowest voltage requirement to turn on; they are also very easy to see.
Series Resistance Considerations
I have said to use a 1k ohm resistor, but other values will work just fine. 1k ohm is a good choice because it is safe for almost any application. Refer to the following table for expected LED currents assuming a 2V drop across the LED. All of these current values are safe for the LED, provide visible light, and should be sourced easily from most any device.
VLED | R | Vcc | ILED
2V 1k 24V 22mA
2V 1k 12V 10mA
2V 1k 5V 3mA
2V 1k 3.3V 1.3mA