Resistors Arrived & Circuit Design!

Today my resistors arrived from www.kelvin.com. I needed 68ohm resistors to run 4 red or yellow LEDs that I received earlier in series. To calculate the resistor value is use the the LED series/parallel array wizard. It is a very nice tool that all you need is the power source voltage, LED forward voltage, LED forward current, and how many LEDs. While this tool is a great help, there are some items to be aware about:

1. Try to maximize the number of LEDs in series in order to achieve higher efficencies (resistors just turn power into heat)
2. Make sure that you power source can handle more then the calculated current draw from the power source
3. Make sure to take note of the resistor wattage ratings in order to appropriately size the resistors
4. Try to keep the same number of LEDs in series across your array in order to make sure that every LED has the same intensity. For example:

 

(wrong)

vs.

(right) 

Keeping LEDs in series even ensures equal intensities.

(image courtesy of the LED Center)

Since a car's alternator outputs a voltage higher then 12v (usually around 13v to 13.8v) in order to be able to charge the battery up to 12v, I will be using a voltage regulation circuit that can handle voltages up to 35v (not recommended) and regulate them to ~12v. Here is the circuit diagram I based my voltage regulator circuit on except that I am using a 7812 voltage regulator (obtained from radio shack):

 

image courtesy of  markallen.

 Now its time for some pictures!

 

New prototyping board!

Voltage regulating components.

 

LEDs! These things a bright, almost to bright!