40W of LEDs on one PWM out

Projects General Guidance
1

the long and short is i'm trying to make a super bright LED DMX light. only need one PWM channel to drive all 4 leds (10w each), the dmx and code part is easy...

a fun thing is that there's no specs on the actual LEDs, only "11-12v" so i'm a little lost on how much current i even need... is there any way to know this? will something like the LM350 (rated 3 amps) drive two of these or should i be using four drivers? is there something better / bigger than the LM350?

i've looked at the many schematics on how to do an led driver but i haven't found many articles/posts that involve single leds that are over 3W each, and given i'm trying to drive 40W of led's there's probably some driver out there that's huge and beefy, but i haven't located it yet.

suggestions are awesome. thank you.

-a

side note: anyone know where to get big heatsinks for cheap? :grin:

2

Do the LEDs have built-in constant current drivers?

Power is simply volts times amps, so you should be able to calculate your amperage.

However, without a proper spec, there's a lot of guesswork.

3

Hi.

I used this transistor to drive long strips of LEDs: IRFZ34N
It should work for you too.
I used a 1000uF cap between the ground and 12V plus a 1kOhm resistor as a load between the arduino and the transistor.

4

snerk4000:
a fun thing is that there's no specs on the actual LEDs, only "11-12v" so i'm a little lost on how much current i even need... is there any way to know this?

P = I * U
=> I = P / U
=> I = 10W / 12V
=> I = 0.833A per LED
(that is assuming that 10W is the input power, not the output power)

These high power LEDs usually need a driver circuit that has an "enable" pin that can be used as a PWM input. So all you need to do is connect the PWM output of the Arduino to the enable pin of each LED driver.

Here is an example of the driver circuit:
http://cgi.ebay.co.uk/High-Power-10W-LED-Driver-MBI6651-PWM-DIM-/380332131049?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item588d8fc2e9

5

yesyes:
Here is an example of the driver circuit:
http://cgi.ebay.co.uk/High-Power-10W-LED-Driver-MBI6651-PWM-DIM-/380332131049?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item588d8fc2e9

know of a place i can get them in the US? :stuck_out_tongue:

i do want to learn how to actually make all this stuff from scratch but i'm having a terrible time getting my head around it. might be past my ability...

6

They have cheap shipping to the US and solid customer service.

7

I used this transistor to drive long strips of LEDs: IRFZ34N
It should work for you too.

That won't work properly at logic levels(*), it wants 10V of gate drive. There are plenty of logic level MOSFETs that will do, something like the IRLR3717 will do nicely.

(*) it might work, might not, depending on the temperature, batch, exact supply voltage, age...

8

An npn transistor can be used to provide the higher gate voltage of a MOSFET. Just be sure to use appropriately sized resistors on the base and collector.

9

brucethehoon:
http://www.sureelectronics.net/

given the specs (just double checking), can i drive all 4 LED's from this provided the input voltage is 30v or so? or should i use two drivers with 2 10W apiece?