This is by far the most widely used method to power LED's. Just connect a resistor in series with your LED(s).
- this is the simplest method that works reliably
- only has one part
- costs pennies (actually, less than a penny in quantity)
- not very efficient. you must tradeoff wasted power against consistent & reliable LED brightness. if you waste less power in the resistor, you get less consistent LED performance.
- must change resistor to change LED brightness
- if you change power supply or battery voltage significantly, you need to change the resistor again.
How to do it:
There are a lot of great web pages out there already explaining this method. Typically you want to figure out:
- what value of resistor to use
- how to connect your led's in series or parallel
There's two good "LED Calculators" I found that will let you just enter the specs on your LED's and power supply, and they will design the complete series/parallel circuit and resistors for you!http://led.linear1.org/led.wizhttp://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng
When using these web calculators, use the Power LED Data Handy Reference Chart
for the current and voltage numbers the calculator asks you for.
if you are using the resistor method with power LED's, you'll quickly want to get a lot of cheap power resistors! here's some cheap ones from digikey: "Yageo SQP500JB" are a 5-watt resistor series.