A circuit design challenge.... RGB tunable LS Torch

I was reading another thread, A question on LEDs... ... and got the idea for a circuit that could drive 3 LS's (1 watt or 5 watt)... Red, Green & Blue... to have one really cool flashlight.
It would need to be adjustable per color for regulated current, have a few different "sauce-style" multicolor cycling effects and include a manual tunable color output (using one control to cycle through the spectrum...Including white). All this, while handling around 500-700ma current regulated for maximum brightness. Once the circuit is designed, sell it as a kit or wrap it in a nice 3 cell aluminum light (of your choice, Mag... Etc..) useing emitters close together for best effect.

I am thinking someone (hopefully someone who reads this) would want to custom design such a beast as I have never seen or heard of anything even close. It would need the adjustable current drive per color due to the different electrical characteristics of different wavelength LS's. I think this would possibly be one of the coolest flashlights ever made....
Possible uses?
You could seriously scare or otherwise totally freak out other Ravers in a club... they would worship the owner of such a monster. The Tim Allen approach here is the idea.
You would be able to tune your flashlight to almost any color... even white. It would be Bright!!! I know it would not be perfect but I bet you could get it very close. I have played with RG&B LS's using different pwr supplies and got real close to pure white and every other color I could think of using a variable resistor per R,G & B. The added color cycling stuff puts this out of my league for difficulty level.

Just thinking out loud...

Anyone up to the challenge of designing such a circuit??
Who would buy one besides me?

I can't even start to imagine the price of such a light. Plus the massive amount of effor needed to design and build the circuitry.... And also I am wondering it Red, Green, Blue can be combine to form a white light. Since LEDs wavelengths are rather specific.

You can combine rgb light from led's to make white, but it's not a perfect white. There is an essay somewhere on the internet that goes into great detail on what kind and how many of each color you need to get a good white, but as you say it's not full spectrum and it looks a little odd and casts 3 color shadows

The hardware would not be that complicated to build I don't think. A single PIC with 3 outputs driving 3 power trasistors to PWM the power to the luxeons. If you used regular LED's you might not even need the external power transistors.

Even the software wouldn't be that complicated, or wouldn't have to be, it could be if you wanted though.

The hardest part would be putting some kind of dial or other data entry thing into the light for dialing in your colors. A regular data entry knob would work OK to dial through the colors. Or you could do something like the lightwand where you just hold the button down until it has cycled to the color you want and then sticks there.

And, perhaps there is the starting point of a mod. Just get a lightwand and replace the current LEd's with power transistors which could directly control the luxeons! I'm not sure that would work as they are already using a step up circuit to power them, so you may need to filter the output to keep a transistor on, I don't know.

Aragorns site already has picts of him putting new, super high brightness LED's into a lightwand. While you couldn't directly replace them with Luxeons, you could use the same controller circuitry I'm sure!

-James

Mixing RGB is known as additive colour mixing, loads of things use it, the monitor your viewing this message on for intstance Fluorescent tubes,white light lasers, some stage lighting systems etc.

Subtractive colour mixing is what is used in printing an some other lighting systems where you start with white and subtract colours to get the one you want.There the colour filters used, for instance ink, are Cyan, Magenta and Yellow.

Won`t go on about who holds the patent on using PWM with digital control to control colour mixing.....

Adam

Don Klipstein has this on combining red, green and blue LEDs to make white. He uses the Nichia Green and Blue LEDs, and HP red LEDs.

http://misty.com/people/don/ledrgb2w.html

I've tried this, it does work, but you do need to
diffuse the light somewhat, or else you get some really strange looking shadows.

/ed brown in NH

Awesome reply's, all....
I knew this would spark some interest....
rlhess..
You basically summed it up, That's what I would want.
It would be really cool if the circuit could also store color settings and recall them. That way you could do the whole thing without any real expensive controls and use buttons for favorite preset saved color choices. (have some factory defaults built in like White and Red... etc.)
However, the control interface "A joystick around the CIE chromaticity diagram" sounds really cool.

Do you have any other links or references to it?
Is it like some of the old RC joysticks that employ a three potentiometer axis interface?

James S..
I am now seriously considering the lightwand\replace LED's with power transistors Idea... (I think I can pull this off without too much trouble)
I am still hoping this idea gets adopted by someone who can do it right and build one of these!
Or at least can help design a circuit so I can build it into a nice MAG Mod.. (or something similar) What existing torch bodies would accommodate such a design and look professional? Lastly, what to call it?
Changeling?
Chameleon?

You should be able to use the circuit(s) described here:

http://www.emanator.demon.co.uk/bigclive/rgb.htm

The ULN2803 version should even provide enough power for the Luxeons,
although you'd have to change the resistors AT the LED section somewhat.
The "mini" version would need external power drivers (something like an,
um, ULN2803. Although three smallish transistors should work too.)

Since Pulse-width modulation is used for brigthnes control, all the code/etc
should work just fine - effectively, the sw controls percentage of maximum
brightness, where "maximum brightness" is just a
function of the LEDs and current
limitting resistors (up to the point where you break something

Schematics, PCBs, and code - what more could you want?

Clive's "Joule thief" is neat too - fun way to use up those batteries
that everyone though were dead.

Enjoy
BillW

Sorry, I don't have any other references...I was daydreaming about it.

Look for the CIE chromaticity diagram on the Web. I'm sure it's somewhere.

I wasn't modeling this on anything yet built. I agree presets would be nice. I think I'd like to avoid having to punch buttons ten times to call up mode ten.

Maybe the joystick surrounded by 8 buttons like a Garmin GPS interface could be useful.

We're talking GPS pricing+ for this, too <smile>.

Cheers,

Richard

Interesting idea!

Color Kinetics has LED lamp heads that do this for room lighting with multiple 3-5mm LEDs (IIRC).

To make this happen in a torch/flashlight (I think 'torch' is the better name for this) I see some design challenges.

1--Power Supply. You'd primarilly want rechargeables, but design it so it will work with disposables as well.

2--Control Interface: The control interface should be simple and intuitive. A joystick around the CIE chromaticity diagram with some other action for overall brightness would be interesting (a control interface I've been fascinated with for MORE than 17 years--see US Patent 3784746)

3--Optics:
3a--Combining: The optics to combine the three LEDs' light might take the form of a camera optical block/beam splitter--the good news is you don't need the dichroics--the bad news is the dichroics MAY increase efficiency over merely semi-silvered. The three beams should be arranged to focus to one spot and concentrate all of their energy there. The 'mixing box' found in diffusion enlarger dichroic lampheads is way too inefficient.

3b--Output: The output optics should take this virtual, combined spot and focus it to the diameter circle you like. Adding diffusion or other softening might be optional.

I don't think just three LSs in their native optics would make this any where near as cool as a combined beam.

Now to do this for a price...ahem.

After all of this, the circuitry is trivial in the right hands (not mine).

Cheers,

Richard