# Built another DIY led driver!



## O2surplus (Jan 31, 2010)

I'm experimenting with a teensy-weensy, tiny IC that works as a buck controller for driving high current leds. The chip is the LM3409HV. It can control LED loads up to 75 VDC and 5000 ma of current, so you can see the potential for such an led driver designed around this chip. I recently designed and had a PCB produced for this chip. I still have to adjust some of the component values as the first one tested produced 2700ma with a 27 volt input ( My target was 2000ma). Here's a photo of the first driver. Notice how tiny that little IC is. Its dwarfed by nearly every other component on the board! Let me know what ya'll think.


----------



## doncityz (May 17, 2011)

The actual driver is that UA7805 IC. The tiny IC is a PWM wave generator only (for switching purposes). Using PWM controller to power up LEDs is a good idea - since efficiency is superb. But, take care of the temperature of that UA7805. Any semiconductor leg will need to be operational at below 90 deg C (im guessing that is the burn point of the PCB - rough guess). And the junction temperature of the internal, well, usually should be aimed to be less than 150 deg C. As for me, when in doubt, slap a heatsink on it, and you're good to go lol...

On a second note, that UA7805 is already heatsinked to the silver track of the pcb. Probably it is enough.. not sure. just follow the circuit rating, you should be ok with it.


----------



## evilc66 (Feb 28, 2008)

In it's most basic sense, it is a PWM driver, but it really is a lot more than that. The LM3409HV is an external FET LED driver. Functions just the same as an internal FET driver, like an LM3404 (very common NI driver). The external FET allows much higher current and voltages. The driver IC still has all the smarts for current sensing, frequency adjustment, and fault monitoring.


----------



## O2surplus (Jan 31, 2010)

Evilc66

You nailed it right on the head - It's a lot more than just a PWM driver. The combination of a very smart control IC and an appropriately chosen FET, make for a really efficient LED driver. Not that I would, but theoretically, this driver design could drive 5 strings of 18 XPG's @ 1000 mA per string- in a parallel wiring scheme. That's a lot of LEDs for a driver that only costs around $25 to build. Of course my little board would probably melt down trying to drive a load like that, but with proper design and component choices, it is possible.
The UA7805 is a 5 volt regulator that is only included in this particular design to provide power for a Nueventics "Synjet" Led heat sink cooling system. The "Synjet" cooler only pulls about 80mA while in operation, so it's current demands will be very light on the 5 volt reg. In any case, The regulator has plenty of "thermal vias" under it to wick the heat generated by the regulator to the bottom plane of the PCB. The "Synjet" is another "smart" component in the lighting system, as it will respond to the same PWM signal as the LM3409, thus it will speed up or slow down it's operation speed based on the dimming signal from the Led driver dimming controller.
I'll be experimenting with this little driver over the weekend and I'll post my results. If I can get it to behave predictably, I'll post the info so people can create their own.


----------



## Naekuh (Oct 19, 2011)

does that mosfet get hot at all?

Maybe a GPU Memory sink ontop will allow it to handle more amperage? 

how do you adjust voltage? i dont see a pot?

so im to assume you have to wire up a 75V array? 

75 / 3 = 25 LED array?


----------



## doncityz (May 17, 2011)

So do you mean, that Q1 is the actual current driver?


----------



## O2surplus (Jan 31, 2010)

doncityz said:


> So do you mean, that Q1 is the actual current driver?


Yes-Q1 is a P-channel MOSFET. The MOSFET is responsible for handling the actual current load of the circuit. The "brains" behind it is the LM3409 buck controller( it's the tiny IC with the 10 pins )


----------



## doncityz (May 17, 2011)

O2surplus said:


> Yes-Q1 is a P-channel MOSFET. The MOSFET is responsible for handling the actual current load of the circuit. The "brains" behind it is the LM3409 buck controller( it's the tiny IC with the 10 pins )


It looks really small though to able to handle 5 Amps. That's crazy. Does it get too hot to touch at 2700mA?


----------



## O2surplus (Jan 31, 2010)

doncityz said:


> It looks really small though to able to handle 5 Amps. That's crazy. Does it get too hot to touch at 2700mA?


I have to admit- I wasn't paying to much attention to the MOSFET when the driver was running. I'm assuming it would get pretty warm too (It's rated for 3.5 amps) but letting the smoke out of a $46 BridgeLux was my main concern. I only ran the driver long enough to get some voltage and current readings, and will try again after I adjust some component values to bring the current down to an in spec level.


----------



## MoeBetta (Feb 5, 2011)

O2, have you had an opportunity to change your component values? Also, what configuration of synjet are you experimenting with?


----------



## O2surplus (Jan 31, 2010)

MoeBetta said:


> O2, have you had an opportunity to change your component values? Also, what configuration of synjet are you experimenting with?


Yep, I got it sorted out. I just mailed out 10 of these little guys to a member for his new lighting system. I managed to get the maximum current down to around 2150mA, which is within specs for the LED he'll be using. He'll be using the "Synjets" to cool heat sinks designed specifically for the LEDs he's chosen. I don't want to give away too much info as he's going to do a build thread on this forum, when he's done with the build. It's gonna be a game changer.


----------



## MoeBetta (Feb 5, 2011)

That sounds promising.


----------



## O2surplus (Jan 31, 2010)

Well folks- here's the newest design.It features Analog Maximum Current adjust-ability and PWM dimming. I designed this on to operate off a 48 Vdc supply and output up to 4.5 amps. I'm sure (with the proper fuses and load balanced led strings) this little driver could run 48 XPG's at 1000ma (4 strings x 12 ) or 1 string of 12 XML's at 3000 ma. Not too shabby- IMHO, for a driver that costs around $20 to build. I'll post up the EAGLE files and a BOM if anyone's interested in building their own.


----------



## silvawispa (Oct 11, 2011)

I want to build my own, but I'd need handholding throughout the whole process.
I think I'll wait till after I've put my arduino PWM controller together...


----------



## MoeBetta (Feb 5, 2011)

That is exactly what I need. Amazing.


----------



## S&KGray (Nov 12, 2008)

Very nice! What is the low end of the maximum current adjust range?


----------



## O2surplus (Jan 31, 2010)

S&KGray said:


> Very nice! What is the low end of the maximum current adjust range?


I'm not exactly sure % wise, but I can adjust the current down to a mere "trickle" as compared to "full blast". The nice thing is- It can still be PWM dimmed down even further.

I have to admit that locating some of the parts needed for 48V/4.5A operation is a bit tough, and drives up the cost, but I'm working on it. I can post a bill of materials for this driver for 48V/3A operation, as that's what I intend to build more of. Let me kow what Ya'll think.


----------



## O2surplus (Jan 31, 2010)

Here's the EAGLE files for the PCB and the Bill Of Materials needed to build a copy for 48V/3,000mA operation. I'll update the parts list for higher Voltage/Current operation as soon as I can get more parts and do some testing.


----------



## MoeBetta (Feb 5, 2011)

Thanks once again O2, I'm looking over that excel spreadsheet trying to finalize my component selections then I'll be just about ready to move forward on this part of the project.

LED's are on their way.


----------



## MoeBetta (Feb 5, 2011)

o2, who do you use for small batches, and how many boards are you generally ordering at once?

I just ran the Batchpcb .dru and had some errors around the LM3409 since it's so small.

Thanks,

Jason


----------



## O2surplus (Jan 31, 2010)

MoeBetta

I use SeeedStudio Services : Seeed Studio Bazaar, Boost ideas, extend the reach
Their minimum order is 10 boards and the cost is very reasonable. I had my last order sent DHL express shipping, which brought up the cost of the boards to $46 total. That may seem expensive but- I received the boards 9 days after placing the order. You'll wait more than a month if you go with their "free shipping' option.
There is an "error" in the boards that I left there intentionally. It's the "Thermal Via" placed under the LM3409 IC.It's placed there to facilitate soldering of the "ground tab" under the chip. Make sure that you invest in a hands free magnifier prior to attempting to solder that chip to the board, it's extremely small, and difficult to see otherwise. I start assembly of each board by soldering in the LM3409 first(it's the most difficult to solder) and testing all 10 pins with a multimeter, before bothering to solder the rest of the components.
Let me know if you want to order from Seeed as I have the Gerber files already generated for the job. All you would have to do is rename them with your order #.


----------



## MoeBetta (Feb 5, 2011)

Up and running! Now to finish the array!


----------



## O2surplus (Jan 31, 2010)

MoeBetta said:


> Up and running! Now to finish the array!


Hey Moe! Did you get the LM3409 drivers built? If so, How do you like them?


----------



## MoeBetta (Feb 5, 2011)

I've built two so far, but I just finished tapping the heatsink, hoping to do a test Friday night. 

So far so good. The boards turned out great!

THANK YOU!


----------



## O2surplus (Jan 31, 2010)

MoeBetta said:


> I've built two so far, but I just finished tapping the heatsink, hoping to do a test Friday night.
> 
> So far so good. The boards turned out great!
> 
> THANK YOU!


YOUR WELCOME! PM me if you need any help.


----------



## MoeBetta (Feb 5, 2011)

I'd built three boards, I even made a make shift ESD mat and grounded my two prong iron's tip.

I get very limited dimming and tons of flicker. I've moved this temporarily to the backburner for mountain biking as of late.

Thanks for the help so far, I'll delve back into it.


----------



## O2surplus (Jan 31, 2010)

MoeBetta said:


> I'd built three boards, I even made a make shift ESD mat and grounded my two prong iron's tip.
> 
> I get very limited dimming and tons of flicker. I've moved this temporarily to the backburner for mountain biking as of late.
> 
> Thanks for the help so far, I'll delve back into it.


Send me a PM and I'll see what I can do to help.


----------

