Diy led meet?

I've had three of you PM me about the LM3409 boards - just posting here to keep track of things. If you guys could confirm you want them for sure and how many, I'd appreciate it, as I'm starting to get close to "running out" of them. :)

Also if any of you will want to assemble them at the meeting (I'd strongly suggest that you at least plan on soldering the LM3409 at the meeting if you're not experienced with SMT, as it's kind of a challenging package) post here or shoot me a note, as we'll need to get started on component selection so you can order your parts.

Actually, why don't we all just post in this thread instead of PMs? That way, we can all learn from the discussion at the same time instead of me having to type the same things out three or four times. :D

There is a component selection worksheet here:

http://hpled.googlecode.com/svn/trunk/lm3409/lm3409_component_worksheet.xls

I'd suggest you guys download that and have a look, then ask questions. There are instructions on it. Basically, you put in Vin (DC power supply's voltage), Vout (LED's total Vf), Iled (target LED current). You can leave expected efficiency alone. You might want to adjust the target frequency up a bit, to say 400k. Then take a stab at the instructions in each of the big gray boxes to choose the components. You're basically looking to adjust the values in red in each section to get the other numbers to "work out" to what you want.

Once you've chosen the values for Roff, L1, Rsense, Cin, and Cout, I can help you put together an order for Mouser.

Or you can just post your Vin, Vout, and desired drive current and I'll do the spreadsheet. :D
 
I've had three of you PM me about the LM3409 boards - just posting here to keep track of things. If you guys could confirm you want them for sure and how many, I'd appreciate it, as I'm starting to get close to "running out" of them. :)

Also if any of you will want to assemble them at the meeting (I'd strongly suggest that you at least plan on soldering the LM3409 at the meeting if you're not experienced with SMT, as it's kind of a challenging package) post here or shoot me a note, as we'll need to get started on component selection so you can order your parts.

Actually, why don't we all just post in this thread instead of PMs? That way, we can all learn from the discussion at the same time instead of me having to type the same things out three or four times. :D

There is a component selection worksheet here:

http://hpled.googlecode.com/svn/trunk/lm3409/lm3409_component_worksheet.xls

I'd suggest you guys download that and have a look, then ask questions. There are instructions on it. Basically, you put in Vin (DC power supply's voltage), Vout (LED's total Vf), Iled (target LED current). You can leave expected efficiency alone. You might want to adjust the target frequency up a bit, to say 400k. Then take a stab at the instructions in each of the big gray boxes to choose the components. You're basically looking to adjust the values in red in each section to get the other numbers to "work out" to what you want.

Once you've chosen the values for Roff, L1, Rsense, Cin, and Cout, I can help you put together an order for Mouser.

Or you can just post your Vin, Vout, and desired drive current and I'll do the spreadsheet. :D
 
can you run multiple drivers off one power supply i think mine are 24 volt 3 amp and i am just going to run normal cree bulbs
 
Yeah, absolutely. The catch is making sure a given power supply has enough current to supply the total demand. If you have three strings and each will be using 1A, you have a demand of 3A. I like to go with a ~20-30% cushion at least, so in that case I'd look for a 3.5A or larger supply.

On your 3A supplies, I'd be comfortable keeping current under 2.5A. So if you were doing strings running at 700-800mA (typical Cree XP-E currents, for instance) then you could fit three strings on each supply.
 
Thanks for helping all of us with this Nate. It is really appreciated.

I've conversed with DWZM a little bit via PM and have decided the following. I want to run 3 strings of 13 XP-E Royal Blue LEDs at around 850mA. So....

Forward Voltage (Vout)- 3.4v * 13 LEDs = 44.2v
Voltage Out of power supply (Vin) - 48v (Has to be over Forward Voltage)
Desired Drive current - 850mA

I have decided on a power supply that outputs 48v and well over the 3315mA (850mA per string * 3 strings * 130%) needed. There are power supplies that have lower amps, but I needed one that could get here by Mar 3rd. Here is the link to the one I chose. http://www.ebay.com/itm/48V-DC-7-3A...506?pt=LH_DefaultDomain_0&hash=item2a13931822

Now, I have no idea what to do with the spreadsheet.
 
You guys are gonna get away easy on this. I'm used to trying to eek out every last watt from the LM3409 using high currents. Designing for low currents is gonna be simpler. I'll run the numbers you posted in the spreadsheet and tell you what I think in a minute.

Before we spend too much time in the spreadsheet, it might make sense to get familiar with the LM3409 design. Most of this is laid out in the DIY driver thread but I'll repeat it here to keep thing simple. This is going to be a long theoretical brain-dump and honestly you don't need to understand any or all of this very well to build and use this driver. I just think this is the most interesting part and I like to talk about it, so I'll post it here in case you guys are interested. :D

The LM3409 is technically a switching controller. There is a generic schematic in the datasheet I linked in the DIY driver thread, but here is the specific schematic for my design:

lm3409sch.gif


The circuit acts as a "buck" topology constant current regulator, meaning it tries to maintain a constant current by chopping down the input voltage to some lower value. The way it does this is by measuring the current through a carefully chosen resistor, called the sense resistor (or current sense resistor, aka Rsense). In my schematic, this is R1. Basically, you choose a value for R1 to determine the current in your LED string.

So, the chip monitors current in R1. It effects the output current by switching the mostFET, Q1, on and off. If it needs to let the current climb higher, it leaves Q1 on most of the time. If it needs to let the current go lower, it leaves Q1 off most of the time.

This "chopping" action essentially produces a square, on-off voltage, which isn't what we want. The inductor L1 is in series with Q1, and together with the diode D1, it turns that on/off voltage into a sawtooth shape that's "tighter" to the actual voltage we want on the output. The output capacitor, Cout, C2, helps smooth this sawtooth further into a more constant output. There is still some "ripple" in the output, but we can make component selection choices to keep that ripple small enough that it is tolerable.

That's the main jist of the circuit's operation. The rest of the components are secondary in nature. R5 and C4 form a timing circuit that controls the frequency of the switching action in Q1 (indirectly, via COFT (controlled off time)). R2 and R3 are a voltage divider to set a minimum operating voltage for undervoltage lockout, which basically helps prevent the circuit from doing bad things if something wrong happens. The values for all of these can be left as defaults with the exception of R5, which is the "Roff" component in the spreadsheet - that is chosen to nail your desired switching frequency. Last but not least, C1, aka Cin, aka the input capacitor, is chosen to help stabilize the power supply to the driver chip itself. The "EN" pin on the chip is fed with a PWM signal to give you a way to control the driver.

So, a summary:

R2, R3, C4 can be left as default parts.
R5 is Roff, the timing resistor, and is chosen to hit your target frequency.
R1, aka Rsense is chosen to hit your target current in the LEDs
Q1 is a mosFET, and D1 is a diode, and are chosen mainly to make sure you get a part capable of handling your power level. They don't directly influence operation.
L1, the inductor, dictates how much ripple you have, and is chosen to get an acceptable ripple.
C1 and C2, aka Cin and Cout are chosen based on ripple.
 
I ran your numbers: 48Vin, 44.2Vout, 850mA, 400kHz.

Roff = 9k
L1 = 25uH
Rsense = .261mA
Cin = 1uF
Cout = 1uF

I have a saved BOM at Mouser with all the appropriate parts on it, I'll adjust for these values and post a link.
 
You said in the main DIY driver thread that the LM3409 can be dimmed via analog signal as well right? I don't have a controller yet, so I was hoping to use a potentiometer to do the dimming. Those are analog right?
 
Yeah, it can be analog dimmed, but the PCBs I have are not really set up for it. It would take a fair amount of hacking, or you could use terahz's design (but then you wouldn't be able to have everything by the time the meet rolled around).

If you're interested I'm sure we could scrounge a Typhon for you, I think someone else in the thread said they had a bunch of PCBs laying around. I have an early version that I'm not using, it works fine but the 10v portion of the circuit (which you don't need unless you want to dim Meanwell ELNs) is fried. And it might not have a display, I'll have to check. If you're interested in it I'll bring it along. You'd just need a DC power supply to run it from.
 
I messaged the person about the Typhon board. If I ever get a controller that uses analog to dim, I'll just replace the board. I'm sure it won't happen in the near future anyways.
 
I'll bring my hacked prototype as a backup.

Here's a BOM for your parameters:

http://www.mouser.com:80/ProjectManager/ProjectDetail.aspx?AccessID=c87dd815c5

If you want to buy it, click on that, click "order cart" near the top right of the list of items, and check out. This is enough to build one driver, if you want multiples, increase the quantities after you hit "order cart."

The LM3409 is cheaper at Future (less than $2 as opposed to $4.35 at Mouser) but ordering from two places means more shipping charges and they're on backup stock right now which means an additional week of shipping. Everything in the Mouser BOM is in stock at high levels right now.

I don't want the DIY driver stuff to overwhelm the thread or the meet so if any of you have other questions or want to see other stuff at the meet, please speak up!
 
Christine_B said:
How much do you save by building them?
Click to expand...

While I'm not in NY I just did some comparisons.

I have several tanks and as an experiment converted one of my 40 Gallon Breeder tanks that I use for fraging to LED's. I will be comparing growth between this tank and another 40 gallon breeder tank running 4 HO-T-5's berfore I convert the rest of my tank.

For what I wanted in light I was not able to find a comercial fixture that completly made me happy. The closest I found were module systems that would run me about $250 to $350 for the 40 gallon Breeder. To build the system completly myself today would cost $175.

Where the big saving come though is the difference this will make in my electric bill. With Wisconsin electic rates it was costing me $97.00 a year to run the T-5's in comparison to $36.40 to run the LED's. that will be a savings of $60.60 over a year. Now add the factor that the T-5 bulbs had to be changed out at least once a year and costs $23.00 each that means an added savings of $92.00 a year. So with a total annual savings of $150.00
It basicly means the LED's will pay for themselves in 13 months.

Now when I convert my 120 Gallon to LED's the factors are going to be slightly different but if the LED lighting works it will still be a big savings and will pay for itself in 16 months.

Who knows If sell my opld T-5's to someone the pay off time could be extremly shorter.
 
I don't mean to be clogging everything up getting help, but I'm going to ask another question about components. I have the driver components in my cart at Mouser. I'm in the process of adding the Typhon components. There are a few things I'm not sure about though.

Lines 4-6 and 19 are about pin headers. They are supposed to be our choice, but I have no idea what to order. I looked at some on Mouser, but got thoroughly confused.
5 M04PTH JP4, JP5, JP6, JP7, JP8 Pin headers of your choice
2 M02PTH JP11, JP12 Pin headers of your choice
1 M06SIP FTDI1 Pin headers of your choice
1 M16PTH JP1 Pin headers of your choice

Also, does Mouser have the ATMEGA328P Arduino-bootloaded Chip?

Last question... I think.... I'm guessing we have to have a power supply for the Typhon, but I don't see that listed on the parts list.
 
It depends on the output voltage needed for dimming your led drivers. If you're using meanwells you'll need at least a 10v supply (I'd recommend a 12v because some voltage is lost powering the controller). If you're doing 5v dimming the same rule applies. Try grabbing a 7v or 9v supply. They don't need to be regulated so check out old electronics chargers (wall warts).
 
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