DIY LEDs - The write-up

[laverda]

TheFishMan65
That is good to know, as this is a little out of my range of knowledge. I don't have my LEDs yet, but I hope the strings will be much closer in total Vf. If they are off by one volt, I need to match them up better.

 

[HeneryH]

I prefer the "strings" analogy as well. You can parallel several strings but using strings stresses the serial nature of how they are wired.

 

[HeneryH]

...When you are running parallel strings off of one of these meanwells, and one LED goes out, the entire string goes out. All of the load from that string is instantly transferred to the other strings, probably blowing all the LEDs on them in just a few seconds. ...

I thought the reason we are paying a premium for a Mean Well driver is that they internally limit the current to the set point? If one of the parallel strings blows I would hope the the ELN would throttle the current to the other.

Otherwise might as well go with a simple DC power supply.

Am I being overly simplistic?

Edit - See comments below; Brain freeze. Sorry.

 

[Skeptic_07]

I thought the reason we are paying a premium for a Mean Well driver is that they internally limit the current to the set point?

I decided to get them because of convenience. They run directly off AC current end up being alot cheaper than buckpucks. I thought about DIY but decided to buy and maybe down the road DIY and sell. I'm sure they'll be a market for these and i could probably recoup at least 1/2 their cost by selling them.

If one of the parallel strings blows I would hope the the ELN would throttle the current to the other.

I don't think meanwells automatically throttle current (amps) only voltage. I'm not totally sure though. Very little of what i post is probably correct :lol:

edit: checking the data sheet it says "Protections: Short circuit / Overload / Over voltage" also says "130%" in the over current line in the table under the 15, 24, 27 and 48. and "Protection type : Constant current limiting, recovers automatically after fault condition is removed" whatever all that means...

more editing: its certainly not fool proof. somebody in another thread had ruined an entire string with a meanwell.. IDK if he was doing parallel though.

 

[TheFishMan65]

skeptic,

I hope this helps.

For those just catching up these deals with a matrix design. I think someone called it serial/parallel earlier see post 1880 for the picture

Let me try this a different. The '.' are nothing I have yet to figure out how to space things other than with a '.'. A power supply supplies the current (assume constant current of 2.5 amps).

.../A1\.../B1\...
PS--A2--Z--B2--X--
...\A3/...\B3/...

If all the A led (column A) have the same drop then they will each get 8.33 amps. But they all get tied together at point Z so we have 2.5 amps supplying column B. The current will vary through the Bs (they did not get binned well), but what we do know is that they will have the same voltage drop across them. All the Bs are then tied together so at X there is 2.5 amps again. This is why binning the LEDs will help put all the 3.7 in a and all the 3.5 in B each LED will get 8.33 amps.

Now if we add fuses

.../F1-A1\.../B1\...
PS--F2-A2--Z--B2--X--
...\F3-A3/...\B3/...

If one fuse blow (F1) then the other fuses (F2 and F3) and their LEDs (A2 and A3) will just get more current so that it adds up to 2.5 amps. At point Z there will be 2.5 amps to split across the B LEDs. So no protection for column B by the added fuses. Now either another fuse will blow (F2) which will cause the last fuse (F3) to blow and everything is out. So I was wrong earlier it is really hard to find the bad led since they are all out. But if all LEDs are fused and if you find the column of blown fuses the one good fuse in that column has the bad LED. The other possibility is that the fuses do not blow and two LEDs share the current meant for three. Depending on your design this may or may not be bad.

Thinking more on how to split safely. A little less than 2 amps across three string (.66 amps each) might be OK. If you loose and LED the other two in that column will each get half the current (.99 amps) which is alright as long as you do not loose another LED in that column. Not as save as the 2 strings I mentioned earlier in my opinion. If you want to continue the route if you have N string of LEDs supply current for N-1 strings. If you loose 1 LED in a column (or multiple columns) you are OK. Loose 2 in the same column and that column risks being lost because of two much current. Want to be able to have to failures use N-2 for your current.

All these failures are assuming an open. If the LED shorted then it would take all the current and the others in that column would go out becuase they would get no current and the driver would decrease it's output voltage to account for the missing drop across the LEDs.

 

[HeneryH]

Edit - Wow, brain fart on my previous note. Yes, my bad.

 

[TheFishMan65]

HeneryH

In once sense they do not throttle the current in the sense of limiting. But ehy do shift it to the other string (which could be too much for the string). sleptic is right on what they are changing.

 

[TheFishMan65]

Don't you wish they would tell you that someone posted BEFORE you post so you can see if your post is still relevant. Or is this a case of too many cooks in the kitchen.

 

[Skeptic_07]

Don't you wish they would tell you that someone posted BEFORE you post so you can see if your post is still relevant. Or is this a case of too many cooks in the kitchen.

you can.. its below your editing box.. just hit preview and all the latest posts will be down there.

 

[TheFishMan65]

I did not know that, but of course I had done a quick reply so it would not have helped. Are you still confused?

 

[TheFishMan65]

skeptic,

I completely missed your post 1901. I can see why you are confused. If you are still confused look carefully at the picture in post 1880. Not only are the LEDs tied positive to negative, but each column is then tied back together. So it behaves like each column has its own constant current source.

 

[reeftanker10]

I am going to buy the 24 led retro kit from rapidled.com could i add 3 more blues and 3 more cool whites to the drivers they give which is two 2 Mean Well ELN-60-48P dimmable drivers so basically have 15 cool whites on one driver and 15 royal blues on the other safely? Also do these drivers not require a power source because it says that they just come with power cords?

 

[customcolor]

i think max is 13 leds per driver and thats pushing it

yes...plug them in the wall and they go

 

[reeftanker10]

hmm so the extra 6 led's isn't worth the money to do another driver...it'd be more worth to just do a 36 led one....Would that be overkill over a 29 gal?

 

[der_wille_zur_macht]

skeptic,

I completely missed your post 1901. I can see why you are confused. If you are still confused look carefully at the picture in post 1880. Not only are the LEDs tied positive to negative, but each column is then tied back together. So it behaves like each column has its own constant current source.

Worth noting! My comments above were aimed towards a plain old "parallel strings of serial LEDs" - NOT at the "matrix" they're showing.

I am going to buy the 24 led retro kit from rapidled.com could i add 3 more blues and 3 more cool whites to the drivers they give which is two 2 Mean Well ELN-60-48P dimmable drivers so basically have 15 cool whites on one driver and 15 royal blues on the other safely? Also do these drivers not require a power source because it says that they just come with power cords?

No power supplies required.

The max per driver is a tricky question. It depends on the Vf of the LEDs you are using at your chosen drive current. If you can determine that, just divide 48 by that number and round down. If you're using lower-drop LEDs (i.e. XP-G) and/or running at a low drive current, you can probably squeeze 13 or 14 LEDs on a driver, but I can't think of a reasonable configuration where 15 would be possible.

 

[der_wille_zur_macht]

it'd be more worth to just do a 36 led one....Would that be overkill over a 29 gal?

Depends on optic choice, drive current, height above the tank, and what livestock you're keeping. 36 LEDs at typical drive currents with no optics is going to be very bright on a 29g.

 

[reeftanker10]

i was going to order with 60 deg optics and was going to play with the height....I'm going to keep SPS LPS and some zoas at the bottom

 

[reeftanker10]

and another question i have in regards to how big my heat sink will be is how wide are the LED stars? and also what is the avg. spacing you guys are using?

 

[n0rk]

If you're using meanwells, I'm assuming you mean ELN-60-48's? If so, you'll probably want to load them up to 12 per driver, otherwise you're wasting capacity. 5 strings of 11 should be PLENTY for a tank your size, especially considering the whites will be XP-G (I'm assuming R5 bin?) You'll probably want to skew the ratio a bit towards the blues to keep them from being washed out by the more-powerful XP-G whites.

At 2', 40 degree optics would be fine. Look for user Santoki, he has a build similar to what you're describing.

If you want to save power, I'd run at a lower drive current and keep the LED count up, vs running at a higher current and lowering LED count. You'll get more efficiency that way. Upfront cost will be a tiny bit more (more LEDs cost money upfront, more current doesn't).

Looking at Santoki's build, it seems I might've grossly overestimated my needs with 55 XP-G/XP-Es :hmm4: 2' was a conservative number, I could easily go anywhere up to about 7' mount height if I needed. Judging by those PAR readings he's taken and coverage figures using the higher output emitters and 40º optics I could do 36 tightly packed and mount them higher up... because there'll only be 11" of water for things to pass through to the sandbed and most colonies will be no more than half that depth, I suspect PAR would be more than sufficient. Bah. I'm thinking this is probably the better way to do things, and if it's not enough add another string of 12 in (build on a smaller heatsink with enough space for 6 either side).

Would I be correct in this assumption, or have I got my wires crossed somewhere?

EDIT: Also, yes, XP-G R5s and Meanwell ELN60-48 drivers. All of my gear will likely come from Cutter, unless I opt to get it as a premium kit from RapidLED.

 

[customcolor]

i got the 60 degrees with my 24 kit and i will say this .....DONT UNDER ESTAMATE THE POWER OF THE Q5s!!!