Need Advice on Building a Led light....

[cdrov]

Hi, there i need your help. I would like to BUILD a LED light (FLOOD) in order to replace my older 50W HALOGEN one and its 12V 7.2Amps Heavy Pb Battery. I am using this light on a Video Camera while i shoot ceremonies.

I have tried several leds and arrays but i have not managed to have the spread and the power of the old one.

My latest efforts were P4 Leds from Dealextreme but what next?

What is the Driver? What Battery? Cooling? At the moment i am using 7,2 Lion Battery (from a sony videocamera 5900mah) with 2 p4's in series but i am not happy yet? How many Amps can i draw?

Any help or suggestions would be appreciate. Thank you all

 

[LukeA]

You could use 6 Crees running three in series off of two of these boards using the lead-acid battery for almost 4 hours runtime.

See TigerhawkT3's thread for ideas on how to put it together.

 

[cdrov]

Since i am carring on my back the battery i wanted something less heavy. How about li-ion or Nimh batteries???

 

[LukeA]

Since i am carring on my back the battery i wanted something less heavy. How about li-ion or Nimh batteries???

You could use anything you wanted to, provided you can carry it and it puts out between 3 and 18V. 16 NiMH D-cells in 2 parallel strings of 8 would give you over 8 hrs.

 

[cdrov]

Wow now it getsa interesting. But let me ask this. Would the 6 P4's i am going to use at 1Amp each?? have the same luminocity as the 50w halogen? What about the color temperature? is it possible to put a gel in front of them and be around 3K to 4K? And the last optics for flood light or nothing??

Thanks

 

[LukeA]

Wow now it getsa interesting. But let me ask this. Would the 6 P4's i am going to use at 1Amp each?? have the same luminocity as the 50w halogen? What about the color temperature? is it possible to put a gel in front of them and be around 3K to 4K? And the last optics for flood light or nothing??

Thanks

The 6 Crees will run at 755mA each for a total of 900 lumens, compared to ~600 for a 50W halogen. You could put a gel in front of the emitters or you could buy 3200-3500K CCT Crees from cutter.com.au. I got one and made a thread about it.

As for optics, but you could get some wide angle optics and put scotch tape over them to help diffuse. Diffusing the light will soften shadows.

 

[Gunner12]

But the filter would cut down some output.

You can also mount the LED bare for flood. Depending on the gel, you might be able to use it directly on the LED.

 

[Greg G]

For flood I think you'd be better off with Seoul P4 emitters and something like IMS17 reflectors. I have a tri-Seoul with that setup and it is far more floodier and useful inside the house than my tri-Cree with McR19XR's.

 

[cdrov]

Thank you all for your prompt responses. I have some more questions.
Will the 7,2V 5900mAh battery will be able to give the necessary power to the 6 P4 Leds?
Where can i get the optics you say?

Regards

 

[Greg G]

6 LED's in series is going to put a lot of strain on any driver. I would build it with two Sharks. Have each Shark drive 3 LED's. And make sure to heatsink the Sharks well too.

The Sandwich Shoppe carries the Shark drivers and the IMS reflectors that pop right onto the Seoul LED's.

 

[SemiMan]

Some thoughts:

- Is that a 50W video light? If so, it is likely close to 1,000 lumens. They tend to run a bit hot and have better lumens/watt.

- Is color temperature important? Realistically, your camera is going to white balance any way and you could always play with the color settings. That said, you may want to give up some efficiency and go with Neutral White and/or Warm White in order to get better CRI. You may find that with the Cool Whites, your camera has a hard time rendering certain colors accurately, especially items with lots of red. GEL are not really going to help as these colors tend to be completely difficient in the spectrum, though adding in Amber and RED to a cool white may give you good overall spectrum that renders better on your camera (though with some efficiency loss).

- Since it is your back that will matter most and good Lithiums can cost more than LEDS, as opposed to trying to get a lot out of a few LEDs, I personally would use a lot more LEDS at lower current. Say 12+ running at 350mA. That way you can always crank them up if you need more light.

- Rebels and K2s (if you can get the TFFC soon) tend to have the smoothest light patterns, but you can certainly get rid of much of that with optics.

- Some wide angle optics, such as Fraen do smooth out the beam better.

Semiman

 

[cdrov]

Thank you VERY MUCH for all this usefull information... I am going to order some walm light while i am waiting for the drivers from DX. Would you think it would be better to go to 12V rathen than 7,2? I believe a 3,2Amh PB Battery is pretty light in terms of weight.