I have attached a screenshot of the part numbers of the LEDís I bought. You can find these on the website by simply imputing the part number. The key is to look for the "mcd" figure and angle. The higher the mcd number, the brighter.
These LEDís do not have inbuilt resistors, so this needs to be calculated, which is very easy. However, this means wasted power, but, for I think my RED ledís, I wasted no power, thus needed no resistors. I connected them all in series which all added up to them running at 11.1 volts. For the Green, I had to insert a Very small (44Ohm) resistor, but still very efficient.
I have attached the spec sheet for the LEDís I have mentioned. It gives all the technical data for each of the LED types.
Here then the calculations on how to build the LED configuration. (Formula Calculations Courtesy of Andrew Foster-Borman)
What we need to do is 'waste' the voltage we don't need in the resistor. Therefore we need to work out what size resistor 'wastes' the correct voltage at the given current
Lets use the 3.6V 30mA LED as an example
We know the current (I), it's (30/1000) 0.03 Amps
We can work out the voltage (V) we DONT need, the voltage to be 'wasted'
7.4 - 3.6 = 3.8V (7.4 is a 2 cell lipo. Use 11.1 for a 3 cell)
Then we transpose the standard formula V=IxR to give us the resistance (R) required.
3.8/0.03= 126.66 Ohms
The standard resistor scale gives us the values 120 and 130. I would use the 130 Ohm and run the LED slightly under.
Power 'wasted' in the resistor can be calculated using P=VxI
3.8*0.03= 0.114 W
so you need a resistor with a power rating of at least 0.125W, the ones you have are
probably 0.6W so no worries.
You can use resistors in series to increase the resistance,
100R +47R = 147R
Or you can use them in parallel to reduce the resistance the formula is
1/R + 1/R = 1/R
So for example
(1/10R) + (1/10R) = 0.2 = 1/0.2 = 5R
1/10R + 1/10R + 1/10R = 0.3 = 1/0.3 = 3.33R
If you are really clever you can do both series and parallelÖ.
(1/ ((1/10R) + (1/10R))) + 47R = 52R
Basically if you want 130R you would use a 100R and a 47R in parallel + a 100R
(1/((1/47)+(1/100)))= 31.97 + 100R = 132R
Hope this makes sense and will help you to calculate your configuration. It is actually very easy once youíve done it once or twice. I have attached my Excel spreadsheet in the event that you find it usefull.
Charl Van Den Berg