little help with leds please!!!

[lordjasper1988]

hey guys, ive put leds in my crawler but they run off the main battery, i soldered the connection to the esc/rx power cable now if the crawlers just sat there the lights are fine but when i accelerate the lights dim and ive lost power in my motor... there soldered in parallel... is there anything i can do so that i dont loose power but still have descent light? like put a resistor in or something?

thanks guys.

 

[dudegetabike]

Without a resistor the leds will draw alot of current. Most leds only need 25 milliamps so solve for the correct resistor using this formula:

V.batt = V.fb + I*R

Where
V.batt = your battery's average voltage
V.fb = your leds forward bias voltage ( should be on the package you got them in, usually around 3 v)
I = your total current (25ma per circuit, if you're in running 2 in parrallel this wil be 50 ma = 0.05 amps)
R= resitance ( this is the resistor you'll need, doesn't have to be exactly what you calculate, just as close as radio shack has.)

So if you're on the stock batt (4.8v)

4.8 = 3 + (2*25*.001)*R --> R ~ 36 Ohms.

This will ensure that only 50 milliamps are flowing through the light circuit. If you're using the stock NiMH battery, you may still notice a drop in power since these types of batteries deliver a limited amount of current.

Hope that helps, cause its more fun to build your light kit than buy it."thumbsup"

 

[benoj]

the problem even with the right resistor (which will help some) the leds will still draw enough current to slow down your micro and dim the lights some and even if they dont your un times will suffer a good blow.

 

[rcdave13]

What size battery are you useing? I hooked mine the same way and I don't notice any loss of power and my run time goes from about 30 min. w/o led's to about 25 w/ 12 led's using a 7.2v 350 mah 20c pack. Also I use a resistance calculator here - http://led.linear1.org/led.wiz

 

[fantacmet]

You could fairly easily just use a tiny little 1s or 2s battery to power the LED's seperately. That's what I intend to do. I'm probably gonna use the lipo packs from my Blade CX2, which by the way if you are interested are small, very lightweight, and fairly inexpensive, and with a change of connectors can be charged on any lipo charger.

 

[lordjasper1988]

hey guys thanks so much, and yeah its better to make and mod than buy "thumbsup"and thanks on the lipo info but id like to try to stay away from lipo not a big fan of them... at least till the combustion and flamibility issues are addressed lol.