Can high wattage LED's (I, III, V watts) be used in direct drive?

I just got an RC truck and I want to put LED's for headlights. Do I need a regulator or can the LED's be used in direct drive?

What about standard LED's will 1 (on each side) standard 5mm led provide enough light to make it look like real headlights?

Thanks

Scott

Depends on your voltages. I use strings of 4 series connected 5mm leds on my rc-heli. They work fine but get very dul toward the end of the run.

I am thinking of adding a seperate pwr suply or a regulator to run them correctly

fire-stick said:

What about standard LED's will 1 (on each side) standard 5mm led provide enough light to make it look like real headlights?

Thanks

Scott

Click to expand...

Standard 5mm LED is powered at 20mA with Vf about 3V. It's 0,06 Watt.
Common power LEDs can handle 350mA - 1000mA, 1 - 5 Watt, with comparable efficacy. Power LEDs will give you 20 - 100 times more light.

Cree XR-E can be direct driven from 3 AA NiMH batteries in series (ie. Sanyo 2500mAh). It's possible only with NiMH because of their high internal resistance. 3 NiCd or alcalines will fry the LED.

What car and what packs are you using that could makea world of difference.

Depending on the voltages, you may need to use a resistor in series with the Led

Hi there,

When you drive an LED with batteries you usually need something inbetween...
a resistor is the cheapest way. The resistor limits the current getting to the
LED and in most cases without this resistor the LED will burn brightly for a short
period of time and then burn up.
The resistor value needs to be selected based on the forward voltage of
the LED and the battery voltage, and the power rating has to be able to stand
the highest battery voltage without burning up the resistor.

I always considered the version: battery - resistor - Led
to be "direct drive"
and NO, I would ALWAYS put a resistor in between, even if it were very "small".
Its a necessary protection against a bunch of much to powerful cells.

65535 said:

What car and what packs are you using that could makea world of difference.

Click to expand...

It's an RC18T. (18th scale, it's about 10" long) The batterypack is a 6 cell (2/3 A's I think, but there 1100 mah, nonetheless) I don't wanna use the battery pack though, I'd like to use either 3 AAA's or 3 AA's (NIMH of course).

Will air be enough to cool a III or V watt LED?

I have X-ray M18MT rc truck and I was also thinking for puting headlights on it. If You want to make it look like real I would suggest You to use common white diodes of about 50000mcd or so (two for each side). It will be the easyest and cheapest way because You won't need a heatsinks or collimators like Luxeons does. Power consumption in that way will be low, probably 10 times lower than two luxeons. And BTW collimator, Luxeon and heatsink would be way too big to put in 1/18 scale.

Has anybody tried putting a good light in one of those R/C helicopters?

brighter said:

I have X-ray M18MT rc truck and I was also thinking for puting headlights on it. If You want to make it look like real I would suggest You to use common white diodes of about 50000mcd or so (two for each side). It will be the easyest and cheapest way because You won't need a heatsinks or collimators like Luxeons does. Power consumption in that way will be low, probably 10 times lower than two luxeons. And BTW collimator, Luxeon and heatsink would be way too big to put in 1/18 scale.

Click to expand...

Yea, ya know, I was thinking about that last night. I've actually never seen a luxeon LED by itself, so I didn't really have a clue as to how big they were. I seen a picture of some last night that were sitting beside a quarter, and they would be too big. Plus all the heatsinks, collimators and high current draw would be too much trouble (if not impossible to fit inside that little space where the headlights would go.)

I think I'll just go with the 5mm type.

-OK what's the brightest 5mm LED??- hehe

I guess I could just use 4 5mm LED's in a series/parallel with the proper resistor.

-How do I know how big to make the resistor?-

I taped my Fenix L2T to the top of it a few nights ago and drove it around my dark parking lot!! WOW!! That was bright, I learned very quick not to drive it directly toward me!! ::BLINDED:: LOL

Resistor help:

Resistor calculator for leds from MetkuMods - Because you love your hardware!

Best regards

____
Tom

with a high VF luxIII, and plenty of heatsinking, you can direct drive on 3 cells... the LEDBEAM is a great example of this, and I have direct driven an emitter pulled from an LEDBEAM on 3 NIMH D cells on a Dorcy 3D (formerly super 1W)..

It should be noted however, that it WILL be overdriven like this, and you must choose a HIGH VF emitter, (as close to 4V as possible)... a set of 3 NIMH AAAs should have enough voltage sag to keep things safe, my LEDBEAM emiiter usually runs around 1.4amp on fresh cells.. it calms down to around 1.2amp after awhile. it won't last forever like this, but will still probably last longer than a bulb, hehe....

So what about the K2. Is this not rated for a higher voltage/current? I have an application to direct drive using 3 wet cell NICads. However, I am worried the high initial voltage on a fresh charge that can be in excess of 4 volts before dropping to 3.6 volts will destory the K2. NiCads deliver most of there power at 1.2 volts, it is just that initial charge voltage that gets you. Actually, the wiring from the battery to the K2 in my application may be enough resistance to protest the K2.