Bright LED's and Power Consumption

[soler]

Hi All,

I got my self a couple of these super bright LED's, 2 White for the front and 2 Red for the rear. Working on the principle that I will be driving these from my 4S pack I also got some high power ceramic 47ohm resistors. Based on Ohms law I calculate with that they should each draw 0.35 amps and based on a 10 minutes flight time all four should consume around 140 mAmp/hr. In the sir these are supper bright and looks quite good.

Does this sound correct?
Also the resistors get very hot

View attachment 13013

 

[ChrisViperM]

I spent hours to figure that LED-crap out.....was not easy, but once you know it, it's a breeze

First of all you need to know the secs of your LED....yours looks like an Edison Edixon 3W Led: http://www.led-tech.de/en/High-Powe...dison-Edixeon-3W-Emitter-LT-1467_142_143.html

The important specs are:

mW min.: 256 mW

mW typ.:	350 mW
mA max.:	700 mA (playing with these figures will determine how bright the LED will shine, I always use max., in your case 700mA)

V typ.:	3,5 V
V max.:	4,0 V (this values are the Voltage range to operate the LED safely, normally I also use the higher Voltage)

Next step is to use a Resistor/Current Calculator: http://ledcalc.com/ Once there, you can chose to calculate Single LED's, Series LED's or Parallel LED's ....

There you fill in the numbers of your specs and hit "Calculate", and you will get the exact value for your resistor....in your case you get the exact value of 15,43 Ohms, but since you won't get the exact resistor, the software will recommend the next closest resistor avalible....in your case you would wind up only with 600 mA since the closest resistor has 18 Ohms....very important is also the Wattage for the resistor, in your case 7 W....but this resistor is a true monster size wise and will get sizzling hot.....
To avoid a monster-resistor, you should be as close as possible to the needed Voltage.....There is small BEC's or stepup/stepdown regulators on the market to get the Voltage down to your needs....most BEC's work with 5V or 6V....



If you use your LED with a BEC supplying 6V, your needed resistor is only 3.3 Ohm / 1Watt and gives you 606 mA, but the size of the resistor and the heat is a fraction.....

Another trick is not to have the LED permanently on (they become very hot) , but rather use a flashing module....on some you can program different flashing patterns for front and back, much easier to see than a solid light), one example I use is here:

http://shop.rc-electronic.com/e-ven...a=article&ProdNr=OPT1050&t=2006&c=2028&p=2028

Download the manual here: http://www.rc-electronic.com/downloads/pdf/bedienungsanleitungen/Anleitung_firefly-lcu_DE.pdf


Chris

 

[soler]

Thanks for the Response Chris, You are correct about what you have said and those resistors do get very hot!!!

I will install a BEC to power these, I was just taking the easy way to avoid lots of wiring, as the ESC are at near he motors and i was just tapping into the same power feed.

Andy