Quick question about LEDs

[jeepscx10]

Ok i just ordered some leds for my axial rigid light bar and i want to run them in series. Is there a certain number of LEDs that can be wired in series before their brightness is affected? I want them to be as bright as possible and i want as clean of a wiring job as i can get to keep it nice and tidy. Any help would be greatly appreciated. also i will be running them off the rx with a bec set at 7v powering the rx.

Thanks in advance,

Kenneth

[Awesome-Sauce RC]

its all based on their forward voltage, most white led's are 3v min to 3.4v,.

when i make my led strings for 7.4v i normally do 2 in series with the current limiting resistor calculated for a full 2s lipo in my case to be safe and then have xxx series strings wired in parralel.

with the 2 led's in series the current draw across all of them will be whatever 1 led is rated for but the voltage required will be xx times the forward voltage of the led, if you wire multiple leds in parralel then the voltage required will be what the led is rated for but the current is multiplied by how many you have in parralel times their current rating.

i normally use 0.5w 5mm leds they are rated max 100ma but i set the resistor value for about 70-80ma, the two led's take only 70ma for the both but need minimum 6v to light but that would be too dim so 6.6v is more than enough for retina blinding and then just calculating the required resistor so they dont burn out from over current draw.



tony

[jeepscx10]

Originally Posted by tony_g

its all based on their forward voltage, most white led's are 3v min to 3.4v,.

when i make my led strings for 7.4v i normally do 2 in series with the current limiting resistor calculated for a full 2s lipo in my case to be safe and then have xxx series strings wired in parralel.

with the 2 led's in series the current draw across all of them will be whatever 1 led is rated for but the voltage required will be xx times the forward voltage of the led, if you wire multiple leds in parralel then the voltage required will be what the led is rated for but the current is multiplied by how many you have in parralel times their current rating.

i normally use 0.5w 5mm leds they are rated max 100ma but i set the resistor value for about 70-80ma, the two led's take only 70ma for the both but need minimum 6v to light but that would be too dim so 6.6v is more than enough for retina blinding and then just calculating the required resistor so they dont burn out from over current draw.



tony

To be honest all that just went over my head but I think I get what your saying

[xtremeaudio]

If you want bright as possible, then I would recommend running a 3 cell and wire all the LEDs in parallel. I use a 1300 battery for my lights and run about 2.5 - 3 hours with no problem.

[jeepscx10]

Originally Posted by xtremeaudio

If you want bright as possible, then I would recommend running a 3 cell and wire all the LEDs in parallel. I use a 1300 battery for my lights and run about 2.5 - 3 hours with no problem.

I eventually will run all my leds off a small 3s but for now I'm sticking with the rx

[xtremeaudio]

You won't have a problem running them at 7.2 volts besides brightness. It will be like running on low beam and switching to high beam in a real car.

[jeepscx10]

Ok cool

[S1NN3R]

Originally Posted by xtremeaudio

If you want bright as possible, then I would recommend running a 3 cell and wire all the LEDs in parallel. I use a 1300 battery for my lights and run about 2.5 - 3 hours with no problem.

That works fine, if you have 12v LEDs. Unfortunately, not all LEDs are 12v. There are 3v, 6v, 9v, 12v, and more. Plug 10 parallel 3v LEDs into a 3s lipo, and you're going to have problems. One of our customers decided "more is better" and re-wired his fancy new Summit light bar to plug straight into the balance plug of his 3s lipo. The only "more" he got out of it was a trip home to get more money to buy more lights.

Originally Posted by jeepscx10

To be honest all that just went over my head but I think I get what your saying

Two things to pay attention to, really. You need to know the forward voltage of the LEDs you are using and the resistors needed for your set-up.

To figure out how many to run in series, just divide your input voltage (battery) by your LEDs forward voltage. With 3v LEDs on RX voltage, run two in series. With 6v LEDs on RX voltage, run all parallel. With 6v LEDs on 3s lipo voltage, run two in series, and so on.

For working out your resistors, there are pen and paper formulas, but the easiest thing to do is to google "LED resistor calculator". There you will find spreadsheets that will let you enter all the specifics of your set-up and it will just tell you what you need.

[jeepscx10]

Thanks that makes sense