DIY LEDs - The write-up

[brassmonkyballs]

Jtro - yep that will work

brassmonkyballs - two issue come to mind the CAT4101 are cheaper, and for really large builds the ELN are the power factor corrected and have huge inrush currents. For more info see my signature (oh a test subject - don't know if anyone has actually tried it yet ).

Thanks Fishman...now I've got a lot of reading and catching up to do

 

[S2minute]

i`m having a time trying to find the right resestors and vfbf for the XM-Ls that i will be running at 1.5amp and have a Vf of 3.1 in a string of 7.
can any of you hook me up with vfbf and res for the xm-ls from both manufactures please?

 

[kcress]

Jtro - yep that will work

brassmonkyballs - and for really large builds the ELN are the power factor corrected and have huge inrush currents.

Should read, "are NOT power factor corrected".


For resistors on 1.5A I'll break from my usual 1.0 ohm recommendation and suggest you drop from a 1.0 ohm to a 0.1 ohm resistor.

The power dissipation starts to get a little more than reasonable at anything above 1A.

This means you will need to shift the decimal point when measuring the currents using the resistor. If you read 0.1V across these resistors it won't mean 0.10A it will mean 1.0A. A mistake you wouldn't want to make. In reality it won't trip up very easily because when you're messing with them the current will be near where you expect them anyway - not off by 10x - if you follow me.

Digikey 1W 0.1 ohm resistor:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=0.1ACCT-ND

1.5A string drive resistor:
I'd rather about 1.7A but those are very hard to find and since the XML can handle 3A a 2A fuse will still protect them.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=F2923CT-ND

Jtro; A SP-320-24 would be good supply with PFC. Nice. Keep it dry - or else... I haven't followed what you're doing, so make sure it has the current you need. Don't push it beyond about 85% of its rating.

 

[TheFishMan65]

Thanks kcress.

 

[Ibixable]

Are there any new LED's that are better as I am about to start really getting into building my LED fixture and dont want to get the wrong LED's

 

[S2minute]

LEDs

LEDs

Thankyou Kcress

 

[TheFishMan65]

The newest CREEs are the XM-Ls. What are you considering?

 

[RedM3]

This is a fantastic thread. Too bad I'm about 330 pages deep and there's no way I'll ever catch up to all of it.

There is one tidbit to this build that I think everyone should be aware of if they attempt this build on their own. I'm not sure if this was previously mentioned elsewhere in the thread. The author uses aluminum rails and heat sinks, but uses stainless steel fasteners. This creates a galvanic cell which in this case leads to corrosion of the aluminum. Since this is basically a marine application where water (or at least water vapor) will very likely come into play, and the threat of corrosion is very real in the areas where the two metals contact each other. I can't tell you how quickly it may occur or how severe the corrosion may be, but it eventually will become an issue.

An easy solution, and one I would recommend, is to either coat all Aluminum-SS contact points with a primer or epoxy of some sort, or use aluminum machine screws in lieu of the SS screws.

 

[bamf25]

Are there any new LED's that are better as I am about to start really getting into building my LED fixture and dont want to get the wrong LED's

The XM-L are th newest. The cool whites have been out about 4 months, the neutral and war white just came out, and are still very hard to come by. The cool whites have two bins. The t5 bin gives 260 lm at 700mA, and the t6 bin gives 280 lm at 700 mA. This is not a hugh increase in output from the XP-G's which gives around the same light at that mA. The big difference is the efficiency when it comes to forward voltage. At 700 mA the XM-L' pull 2.9v, and the XP-G's pull 3.2 or so. The XM-L can handle voltage upto 3000 mA, while the XP-G's can only go to 1500 mA. For our use if you are staying with the eln-60 drivers or just staying with drivers in the 700 to 1500 mA range there is little advantage from a light output standpoint (XM-L will be a slight increase), but the eficiency is a marked increase. You may also get longer life from the XM-L because you would not be driving them as close to their limit.

 

[wfournier]

The XM-L are th newest. The cool whites have been out about 4 months, the neutral and war white just came out, and are still very hard to come by. The cool whites have two bins. The t5 bin gives 260 lm at 700mA, and the t6 bin gives 280 lm at 700 mA. This is not a hugh increase in output from the XP-G's which gives around the same light at that mA. The big difference is the efficiency when it comes to forward voltage. At 700 mA the XM-L' pull 2.9v, and the XP-G's pull 3.2 or so. The XM-L can handle voltage upto 3000 mA, while the XP-G's can only go to 1500 mA. For our use if you are staying with the eln-60 drivers or just staying with drivers in the 700 to 1500 mA range there is little advantage from a light output standpoint (XM-L will be a slight increase), but the eficiency is a marked increase. You may also get longer life from the XM-L because you would not be driving them as close to their limit.

The "ELN-60" drivers are available in configurations will supply up to 5A of current so you are not limited to lower currents by using those drivers.

Also to avoid confusion here, Voltage and currant are two different things. The forward voltage (vf) of the LEDs are given in volts and current is listed in mA (there is no such thing as a "voltage of 3000 mA"). Both are important. It is important to keep the terminology strait IMHO, particularly for people who are coming into this with little electrical knowledge.

 

[TheFishMan65]

RedM3, Follow the direction in my signature. It should save reading a few pages.

bamf25,

The XM-L can handle voltage [current] upto 3000 mA, while the XP-G's can only go to 1500 mA.

With the same ELN you should be able to get another LED or 2 on it if you use the XM-Ls. So you could get an 8-16% improvment in light there.

 

[bamf25]

True the eln's can put out higher mA with other models, but you lose the ability to drive between 12 and 14 led's. If you want to run the other drivers you can get to that 3 mA but only drive 6 or so leds.

If you are using XM-L's on a eln-60-48 you can probably drive 15 leds at 1000 mA on that driver. The fV at 1000 mA is 2.95, so 15 x 2.95= 44.25 total volts needed, and the driver can do 48. At the max mA that driver can provide (1300 mA), they have a fV of 3.05, so more than likely you could still drive 15 leds or 15 x 3.05 = 45.75. That is the biggest plus of the XM-L's.

Thats for correcting my crossing up some terminology.

 

[wfournier]

True the eln's can put out higher mA, but you lose the ability to drive between 12 and 14 led's. If you want to run the other drivers you can get to that 3 mA but only drive 6 or so leds.

That you for the correction.

True with the ELN-60 series when current increases voltage drops so you can drive fewer LEDs. However something to consider is that an ELN-60-24 can drive 7 XM-L's at 2.5A Producing 5635 lumens. The ELN-60-48 can drive 13 XP-G's at 1.3 A producing 5421 Lumens. Output and power used is about the same. The difference is that 7 XM-L's will cost less than 13 XP-G's and 13 XP-G's give you more options for LED placement and possibly better coverage. I guess my point is there are reasons to go either way and it really depends on your application as to what choice is best. It makes almost no sense to use XM-L's (IMHO) if you drive them at lower currents.

 

[bamf25]

True with the ELN-60 series when current increases voltage drops so you can drive fewer LEDs. However something to consider is that an ELN-60-24 can drive 7 XM-L's at 2.5A Producing 5635 lumens. The ELN-60-48 can drive 13 XP-G's at 1.3 A producing 5421 Lumens. Output and power used is about the same. The difference is that 7 XM-L's will cost less than 13 XP-G's and 13 XP-G's give you more options for LED placement and possibly better coverage. I guess my point is there are reasons to go either way and it really depends on your application as to what choice is best. It makes almost no sense to use XM-L's (IMHO) if you drive them at lower currents.

Great point, and I have been thinking about it for days, as I am about to place an order for my LED's. I think you can get 14 XP-G on one eln-60 at 1000 mA that is 14 x 3.3 v per led = 46.2. At 1300 mA that is 14 x 3.4 v per = 47.6. Now that is pushing the driver hard at that point, and I am not sure I would want to do that. In theory it should work.

As for the spread you make an excellent point. In long tanks we need to spread out our light and do not want to spotlight things. At the same mA the XM-L may give you a 5% increase in light per led, and allow you to get 1 additional led on the string. For our application that is a very small advantage.

 

[TheFishMan65]

It makes almost no sense to use XM-L's (IMHO) if you drive them at lower currents.

IMHO it can it all depends on the price difference. I just bought some XP-G Warm white for $5.14 and some XM-L warm white for $5.61. For that price difference I would recommend the XM-L because of the savings in electricity. XP-G for $4.65 vs XM-L T6 for $7.88 well it will take a long time to make up the difference.

 

[wfournier]

Great point, and I have been thinking about it for days, as I am about to place an order for my LED's. I think you can get 14 XP-G on one eln-60 at 1000 mA that is 14 x 3.3 v per led = 46.2. At 1300 mA that is 14 x 3.4 v per = 47.6. Now that is pushing the driver hard at that point, and I am not sure I would want to do that. In theory it should work.

As for the spread you make an excellent point. In long tanks we need to spread out our light and do not want to spotlight things. At the same mA the XM-L may give you a 5% increase in light per led, and allow you to get 1 additional led on the string. For our application that is a very small advantage.

Looking at the XP-G data shoot I think that if you're trying to stay under 48v at 1.3A than 14 is going to be pushing it, I think the vf at 1.3A (as depicted in the data sheet) is going to be closer to 3.47 V. However the ELN-60-48 lists that the voltage range can be adjusted up to 52.8V. I'm not sure if there are any other consequences of doing something like that but it might be worth looking into.

 

[wfournier]

IMHO it can it all depends on the price difference. I just bought some XP-G Warm white for $5.14 and some XM-L warm white for $5.61. For that price difference I would recommend the XM-L because of the savings in electricity. XP-G for $4.65 vs XM-L T6 for $7.88 well it will take a long time to make up the difference.

True, and I guess this further goes to show how you really can't name an all around "best" LED. There are simply to many factor that go into that are specific to every project (and where you are purchasing from).

Has anyone seen any practical (for our applications) optics for the XM-L's yet?

 

[bourbeaue]

ETG have specs on an XM-L optic. Not sure when they will have stock.

 

[bamf25]

True, and I guess this further goes to show how you really can't name an all around "best" LED. There are simply to many factor that go into that are specific to every project (and where you are purchasing from).

Has anyone seen any practical (for our applications) optics for the XM-L's yet?

I am having trouble finding good optics options fopr the XM-L. Not sure that matters to me yet, I am putting my setup in an old MH fixture with rim mounts so it will only be 6 to 8 inches above the water.

 

[TheFishMan65]

Probably won't need them, by the time you build they will be more readily available.