How to wire LEDs

[heyok]

Right, 20 LEDs at 0.020 mA = 0.4 Amps
That's a decent load, but really not much in the scheme of things for the BEC to handle. And, as you said, it is a supply of regulated voltage so you won't have the lights dimming on you. Plus, you might have the luxury of a low voltage cutoff in your ESC that will help keep you from over discharging your pack.

[ik632]

Yeah, that's what I'm thinking. I've found a few places with 25k+mcd white LED's where you can buy a bunch pretty cheap. Essentially I'd just need to get those, the right resistors and then light controllers as needed to turn what I want on and off.

So when they say the forward voltage is 3.0-3.4v (3.2v typical) at 24mA (max) should you size resistors for whatever your voltage source is (say 5v from BEC) and 3.2v for drop and 24mA for current? Or, should you down size a littel to say 3.0v and 20mA?

[RootBreaker]

interesting.. thanks for this one!!!!!

i bought 50 blue led's from ebay for $5 a while ago shipped... and used 8 of them in my fish tank as a moon light... they already had resistors for 12v so I just hooked up a dc power supply and went..

hmm I will have to look at doing this eventually.....for my RC's....

thanks for sharing

[ik632]

So, if I do the math correctly on my above example I'm looking at:

(5v-3.2v)/0.024mA = 75ohm or for 6v BEC 116.7ohm (so round up to next size of 120)

[envious8420]

Originally Posted by heyok

Hope it helps you!

I can read the 5% type resistor colour codes without thinking about them but you probably have a 1% resistor there and I'm not sure how to read it. Found this:
Resistor color code calculator - 3, 4 and 5 band resistors
Entered in your colours but it didn't like them.

I always grab an ohmmeter when in doubt.

after years of using resistors, this has to be about the best resistor calculator
ive ever used. thanks for posting. very helpful.

[heyok]

Originally Posted by ik632

Yeah, that's what I'm thinking. I've found a few places with 25k+mcd white LED's where you can buy a bunch pretty cheap. Essentially I'd just need to get those, the right resistors and then light controllers as needed to turn what I want on and off.

So when they say the forward voltage is 3.0-3.4v (3.2v typical) at 24mA (max) should you size resistors for whatever your voltage source is (say 5v from BEC) and 3.2v for drop and 24mA for current? Or, should you down size a littel to say 3.0v and 20mA?

Using the LED calculator tool:
5V from BEC
3 V LED
24mA
we get 82 ohm

and...

5V from BEC
3 V LED
20mA
we get 100 ohm

My thinking is that you will mostly find 6 volts running to the recevier so...

6V from BEC
3 V LED
20mA
we get 150 ohm


I have a pant load of 150 ohm resistors already so that's what I would use!

[ssyork]

Thanks for the write up. You broke it down into easy steps!

[envious8420]

pmed

[envious8420]

LED series parallel array wizard---http://led.linear1.org/led.wiz
555 Astable Circuit Calculator---http://www.ohmslawcalculator.com/555_astable.php
Welcome to the Electronics Club
EPE "Basic Soldering Guide"---http://www.epemag.wimborne.co.uk/solderfaq.htm
Servo Database - RC Servo Specs and Reviews

[BigGuyJT]

Thanks for the How-To thread!!! I just ordered 100 white and 100 red led's and the resisters needed. Now the EXO, Honcho, and Slash are going to be burning holes though the midnight sky!!!

[heyok]

Originally Posted by BigGuyJT

Thanks for the How-To thread!!! I just ordered 100 white and 100 red led's and the resisters needed. Now the EXO, Honcho, and Slash are going to be burning holes though the midnight sky!!!

That's great! Hope you can post up your results.

[RootBreaker]

Originally Posted by BigGuyJT

Thanks for the How-To thread!!! I just ordered 100 white and 100 red led's and the resisters needed. Now the EXO, Honcho, and Slash are going to be burning holes though the midnight sky!!!

also can you give a link where you bought?


my son has a hummer rc that we got from RS a while ago.. the mattrax hummer.. and it has lights.. i could steal them!!!!!! hah

[BigGuyJT]

Originally Posted by heyok

That's great! Hope you can post up your results.

Will do

[BigGuyJT]

Originally Posted by RootBreaker

also can you give a link where you bought?


my son has a hummer rc that we got from RS a while ago.. the mattrax hummer.. and it has lights.. i could steal them!!!!!! hah

I got 'em off e-bay. Clicked on free shipping and US only and so many came up. If you need the actual link I'll have to get that to you when I'm off work.

[envious8420]

Im really glad you started this Al. I've got all kinds of tricks for for these little plastic wonders.
When I'm getting ready to wire an rc for lights, I like to whip out the old breadboard and make /test the system before installing it in the build, especially when using 555 timers and others. After I know its gravy ill start soldering. I came up with a method of using IC chips without a circuit board, I take needle nose pliers and straighten the pins that are going to be used, solder the leads on and shrink wrap, then snip off the others. then a large piece around the whole deal.(like HeyOk does with his great products.) <> LOL!

[heyok]

Originally Posted by envious8420

Im really glad you started this Al. I've got all kinds of tricks for for these little plastic wonders.
When I'm getting ready to wire an rc for lights, I like to whip out the old breadboard and make /test the system before installing it in the build, especially when using 555 timers and others. After I know its gravy ill start soldering. I came up with a method of using IC chips without a circuit board, I take needle nose pliers and straighten the pins that are going to be used, solder the leads on and shrink wrap, then snip off the others. then a large piece around the whole deal.(like HeyOk does with his great products.) <> LOL!

One of my favorite stores is Radio Shack here in the states, not sure of their equal in other countries though. This is where I buy the majority of my supplies/parts. they sell these little black project boxes that are perfect for stashing all of the various components. They are also fairly easy to seal/waterproof, you can even mount switches for various controls(multiple winches, rock lighting and so much more.)<

It's a fun hobby. Glad to read that others enjoy it.
We used to have Radio Shack but something happened and now the stores are called The Source.

[envious8420]

This is where I buy the majority of my supplies/parts. they sell these little black project boxes that are perfect for stashing all of the various components. They are also fairly easy to seal/waterproof, you can even mount switches for various controls(multiple winches, rock lighting and so much more.)--maybe another time) I'm just a fountain of weird, neat, odd and useless shit some times. I should write a book. I also love to recycle electronic stuff. sorry 'bout the hijack Al.


for some reason I couldnt get this to fit into 1 post???

[envious8420]

it messes with the system if you use too many arrows? I'm working on getting the wraith lit up now.
Headlights, markers, tail, brake, was even considering a center third brake light, rock lights, fog lights, bed light, instruments and radios lit up in the dash and console. the dash and console look really good lit up in the dark. i could go on forever right now, but Ill spare you all from my ramblings.

[braq]

Hi,

years ago I heard a lecture on using LEDs for model train interior lights.

What impressed me is that the actual output (in candela, that's what the mcd rating stands for), aka "brightness" is pretty good already at half their max. current rating (in many cases that would mean 10mA instead of 20mA). Brightness and current are not (fully) proportional, or in other words optical efficiency degrades towards the max operation current.

I use only 100 Ohms resistors for

white LEDs > one
red or amber LEDs > one but the LED in series of two

which after calculation equals to

(5V-3.2V)/100 (V/A)=18mA (white)
(5V-3.8V)/100 (V/A)=12mA (red/amber)

Also helps to keep the number of (different) parts down and in case of accidentially hooking one circuit to the wrong output the LEDs don't burn up.

cheers

braq

[BigGuyJT]

Thanks for the great write up Heyok. Now lets see if I can get the pics posted...