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I am building a led mood light with a high power RGB LED (30W) using 3 constant power supplies for each color.

These are the items I had in mind (but open to suggestions):

30W Integrated RGB LED Light Bulb (10 Series and 3 in Parallel) JR-30W 30W Waterproof LED Power Driver (AC 85~265V)

Each color will be controlled with PWM by arduino. So far so good, the problem is that the bc337 transistors I have can only go up to 800ma so I need something significantly beefier. What is my best and simplest option here? I'm not very knowledgeable in electronics so simplest solution would be best.

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Well, the specifications of the device you linked are grossly inadequate.... but given you have 10 LEDs in series, I expect you'll operate at something like 40VDC...

Arduino analogWrite function generates PWM at about 490Hz.

I would suggest setting up a high side switch with a P-channel MOSFET (e.g. IRF9Z24) conrolled by an NPN BJT (e.g. 2N3904). Say 100ohm resistor into the base of the BJT and a 4.7kohm pullup on the gate of the MOSFET. Connect LED between MOSFET drain and GND. Connect PWM input to the aforementioned 100 ohm resistor.

enter image description here

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  • \$\begingroup\$ Great answer! Will keep it open for a bit until I know I have it all figured out :) \$\endgroup\$ – DominicM Dec 5 '12 at 17:43
  • \$\begingroup\$ actually 32~36v for LED's which is what he spec'd as his chosen power supply 24~36V except these are 3 strings. YOu can choose $0.20 HEXFETs in SMT with 150 mOhm Ron or use the Thru-hole parts, without heatsink. Use a series 4K7 between collector and Gate 4K7 to reduce Vgs 50% , no zener needed. You might want to consider the 50W version, but your bigger problem is a good LED heatsink...& fixture A CPU heatsink can be retrofit with a low speed fan. I recently posted a PWM circuit with 3 pots, but you can use Music to drive each color using Bass, mid, treble filters and rectifiers. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 5 '12 at 19:24
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This should perhaps be a comment, but I couldn't see how to do that.

Most FETs like the IRF9Z24 have a 20V maximum gate to source. So,
you should add a 10V zener across R2, and another 4.7K resistor in
series between T1 collector and Q1 gate R2 node.

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  • \$\begingroup\$ Unless I am reading the wrong thing the only voltage value I see is 60V. Take a look at the spec and let me know if it's 60v or 20v: Spec: vishay.com/docs/91090/91090.pdf \$\endgroup\$ – DominicM Dec 5 '12 at 18:35
  • \$\begingroup\$ Look in the absolute maximum table on sheet 1, second row ... Gate-Source Voltage ... +/-20V limit. It appears that the circuit as drawn would put 40V gate to source when T1 is on. \$\endgroup\$ – gsills Dec 5 '12 at 18:45

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