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I am building a DMX controlled light using an Arduino, but I am not sure which power supply I should use to power the LEDs which run at 36v (10 in series, 3 rows) 30W. The main problem is whether or not there is a way to control an LED colour using PWM from an arduino, but it must be able to turn fully off.

Ideally I would like to build the constant current supply myself, but it must be as cheap as possible as I will have to control 48 of them!

Finally, would it be possible to use one power supply for a number of LEDs, even just one colour of multiple separate LED modules, as this would save costs, although they must all still be able to be individually controlled for brightness.

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  • \$\begingroup\$ If you want to have the same supply powering all the individually controlled colors, it is simpler to use a big constant voltage supply. This voltage can then be individually converted to constant current for each LED group (either using linear or switching regulation). \$\endgroup\$ – dim Jun 1 '16 at 12:28
  • \$\begingroup\$ Thank you dim, I will look into that further, but by any chance do you have any recommendations for which type I should use? \$\endgroup\$ – Nikita K Jun 1 '16 at 12:31
  • \$\begingroup\$ Not really. I did not really understand the whole picture actually. Is 36V the voltage of 10 leds in series ? Or is 36V the voltage of a LED light bulb, and you will put 10 such bulbs in series ? Where are the rows ? Is 30W the power of the whole group 10*3 ? Of a single LED or LED bulb ? You'll have to control 48 time a whole 10*3 group ? single leds ? A quickly drawn schematic would be useful here. \$\endgroup\$ – dim Jun 1 '16 at 12:39
  • \$\begingroup\$ Sorry for not making it too clear, but it is a 30W COB LED which inside has 30 LEDs, 10 in series per colour (RGB) Therefore it will require 36V for the 10 LEDs inside the module, ill add a schematic to the question to make it even more clear \$\endgroup\$ – Nikita K Jun 1 '16 at 12:44
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    \$\begingroup\$ In case this suffers from trigger-happy close votes, I'd like to say that I'm also interested in the answer of how to design modulated constant-current power supplies. \$\endgroup\$ – pjc50 Jun 1 '16 at 13:17
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Here is the design process I would follow:

First, get an idea of the max total supply required: here 30W * 16 COB LEDS. This makes about 500W. We can easily find such supplies off-shelf, however is very difficult to design such an AC-DC power supply at a DIY level. So, we make it simple: use a single power supply for the whole project, that we buy from somewhere.

Regarding the current sources for each LED string: I personally don't like to make designs that waste too much power, and sometimes, the cooling requirements make it more complicated than actually using switching regulation. So I rule out linear regulation and go for switching, which, as a benefit, gives you more flexibility regarding the main supply voltage.

The requirement for the regulator of a single LED string are not so big here: about 36V, 300mA. We need 48 of them, so we have to make them cheap (I guess). Go to mouser/digikey, find buck LED controllers that can handle more than 40V, and more than 300mA. Order by price. You get a few of them (for example AP8802, ILD6070, ...) Check the datasheet for the external components required and the typical use case schematics. Ok, not so many external components (integrated mosfet), the only big one is the inductor. Check that they can be dimmed using PWM. Select the inductor based on the datasheet info, check its size and price.

Go back to the main supply. Decide its voltage, which must be between the max regulators supply and the max regulators voltage drop + max LEDs voltage drop. Size it more precisely (taking account efficiency of current regulators). Find it for cheap on some website.

Go back to the individual regulators: make the schematic, make the layout (use big traces for big currents, follow the rules given in the regulator datasheet and make it as close as possible to the reference designs you can find, and try to maximize dissipation of chips if they have a powerpad underside), buy everything, solder, make the firmware, enjoy !

And if you have a more specific problem during any of those steps, don't hesitate to post a new question...

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  • \$\begingroup\$ Thank you for your time and effort dim! That is perfect as to what I was looking for and will start designing one! Thanks again! \$\endgroup\$ – Nikita K Jun 1 '16 at 14:21
  • \$\begingroup\$ Well, it may not be as easy as I write it, but I wish you good luck anyway. \$\endgroup\$ – dim Jun 1 '16 at 14:23

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