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Building an LED lamp with varying color and brightness

Craig S

May 14, 2018
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Can somebody help me construct a big-picture view of where I should be turning my attention here.

I want to put together a DIY lamp of some considerably brightness, up to maybe 50 W. I'm an electronics noob so I'm looking to start with off-the-shelf kit if possible, at least to begin with.

What I basically want is to drive/control maybe 3 different colors of white LED, and be able to dim them all, in a sensible fashion, much as the cheap LED tape controllers provide.

I'll settle for physical controls for now but it would be nice to be able to plug in wifi control and an app at a later stage.

I've been looking at PWM drivers but the variety is enormous and I lack the knowledge at this point to further refine my searching.

What are some ideas for a path to take here. E.g. I have notes on DMX512, Arduino, ? And given I want to drive a lot of power, should I be looking at high power controllers, or boosting power after the controller stage...

I realize this lacks specificity but as I said I need some broad overview advice before I can even start thinking about particulars.
 

kellys_eye

Jun 25, 2010
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You could drive three high power LEDs (red, green and blue) using the cheap (and smaller) controllers simply by adding an external higher-power capability driver device (MOSFET usually).

The proportion of R, G abd B you set will determine both the colour and intensity of the resultant light.

You might find that an RGB DMX-controlled spotlight does all you require in 'one' package without the hassle though.
 

timff

Apr 13, 2018
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An LED bulb that gives the equivalent amount of light as a 60W incandescent bulb may only require 8W of electrical power. However 8W is not inconsiderable. You may want to consider multiple LED arrays of red, blue, and green to distribute the watts per element over a larger number of devices.
 

Craig S

May 14, 2018
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Is this really what you meant?

Yes, I want to build a white lamp with varying brightness and CCT. So my idea is to have something like 10W at ~2000K, 20W @ ~4000K, and 40W @ ~6500K, and then vary power between them with a sum power limit of whatever is feasible, so I can have dim warm light and very bright cool blue light.

But for the sake of design I suppose it could be viewed as an RGB lamp, I just need 3 channels of control in the end. The difference being the bluer CCT needs to be more powerful than the yellow.

An LED bulb that gives the equivalent amount of light as a 60W incandescent bulb may only require 8W of electrical power. However 8W is not inconsiderable. You may want to consider multiple LED arrays of red, blue, and green to distribute the watts per element over a larger number of devices.

I have my eyes on the more powerful COB chips, properly heatsinked of course and maybe fan cooled.

You could drive three high power LEDs (red, green and blue) using the cheap (and smaller) controllers simply by adding an external higher-power capability driver device (MOSFET usually).

The proportion of R, G abd B you set will determine both the colour and intensity of the resultant light.

Can you clarify what you mean.
Are you thinking
(cheap controller) -> (power booster*) -> (LEDs)

In this case would there be 3 independent 'boosters*' downstream of the controller, or a 3-channel unit? And can this be done while retaining fine control of low power dimming.

* Like this?
 

kellys_eye

Jun 25, 2010
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In this case would there be 3 independent 'boosters*' downstream of the controller,
Yes. The devices that drive the LEDs have a PWM output that can be used to drive another device (MOSFET) to increase the current handling capability and thus drive more powerful LEDs than they were originally intended. But those types of controller normally have relatively fixed colour selection options so you'd be limited in what you could do with them.

Building simple PWM controllers using discrete (or integrated) components is straight forward and there are many schematics on line for this purpose. Simply build three, one for each of the LED colours. The 'fineness' of the PWM control will set how accurately you can make a particular colour. Using an analogue PWM controller gives you, effectively, infinite colours to chose from.

If you wanted to be specific about it you could make each PWM an 8-bit level using an Arduino (or similar) and get 255 x 255 x 255 (= 16 million) colour levels.

sooooo many ways to skin this particular cat!

eBay is full of LED controllers - take this one for example:

https://www.ebay.co.uk/itm/1-DC12V-...hash=item48a9eefce5:m:m3HTBAHlp6JomN4_SfCZ_ZQ

good for 100W so get 3 and you can do the whole lot.

But there are, as said, hundreds of versions of similar thing to chose from:

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=led+controller&_sacat=0
 
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