I have a couple of moving heads like this They have a QCL (Quad color led chip) Theres a total of 10w. Most of the time I don't use the colors, I just use the white quadrant, which I presume is 10w. If I want a bright white I can turn on the R G & B quadrants as well but it gives a rather sickly white with weird colored edges.
I was thinking of replacing the QCL led with a single 10w White led. Obviously each color, R,G,B,W is controlled by a separate dmx driver.
I'm just wondering would it be a very bad idea to join all these drivers together and solder them onto a single chip? I'm concerned about the output from one going into the the others. I can programatically be fairly certain to make sure that all the drivers are set to the same output at all times though but I can never be 100% sure!
What do you think?
Also on a side note, these lighting fixtures are rarely on for more than a few minutes at a time so well below their max in terms of overheating, would it be better to take the output from one of these RGBW channels and just use that with a transister to maybe drive a 20w or 15w white led chip?
Electrical – Multiple led drivers for a single LED
dmx512ledled-driver
Related Solutions
You are attempting to map a triplet of values (the responses of the LDR to your RGB LEDs) to another triplet (the RGB values you used to print the colors on the paper). There are loads of environmental values that will influence this mapping. IMO the best you can do is
Make sure each LED gives a decent and compareable effect. Depending on your LEDs and the sensitivity of your LDR to the various colors, this might mean that you have to use different currents (series resistors) for the LEDs.
Establish the calibrarion values for your colors (as you have done) and use this to 'linearize' the R, G and B values.
Limit the external effects to a minimum. (you seem to have done this)
I use exactly this as an excercise for my students. I have reputation of not being easdy on my students. They pass when the can reliably distinguish 3 colors :) One sheet from that assignment:
To drive LEDS, you have two options, each with their own pros and cons a) linear b) switching
a) linear, dissipates excess heat, simple (LM317) (or relatively simple)
b) switching, low dissipation, potential switching noise
To choose between these two, and then to choose which way to implement either, you need to look at your other constraints. Heat? Cost? Board area? Able to control finely? Design skills?
You can get integrated solutions for both methods. Maxim IC do a gazzillion drivers in both types, try sampling them for one or two.
Linear devices will always get hot. At 0.5A, with a few volts drop, you will always need to think about heatsinking, whether you use an integrated or discrete solution
FWIW, my personal preference for a linear multi-colour driver, and OK, it takes large board area, is a discrete solution. Each channel uses a TO-220 MOSFET, with a small resistor in the source to monitor sink current, driven by 1/4 of an LM324 op-amp, driving the gate to servo the source voltage to maintain the drain sink current, 3 channels uses 3 FETs and 3/4 of the LM324. The compare voltage to the 324 inputs allows you to set the currents. The heat dissiaption is spread over several big cheap devices. TO220s are good for 1 to 2 watts in free air, to 100watts on a heat sink, so it's scalable to many amps and higher voltages, still staying with cheap MOSFETs.
There are so many integrated LDO (low dropout) regulators available that can be configured as current sources that it would be futile for anybody other than you to start trawling through them. Look for voltage input range, heat dissipation, package size, AND ABILITY TO WORK WITH WHAT TECHNOLOGY STABILISATION CAPACITOR, ie ESR (ceramic, tant, alli elec), as you don't what them to oscillate in service.
To do without the heat, investigate integrated switching solutions.
Best Answer
You can't in general connect multiple drivers to a single LED, they are likely to damage each other.
Why don't you replace it with four white LEDs, each connected to a single driver? That way it should be electrically good and you can adjust the brightness by an extra 6dB.