DIY LED Array build

[der_wille_zur_macht]

sphil, that driver is designed with a max output of 48v. The voltage reading you will get on the output side the driver is determined purely by the current and the specifications of the LEDs. If you have an LED with a forward voltage of 3.7V at 1A, you'll see 3.7V if you put 1A through it.

So, if you have 15 LEDs with a certain forward voltage and drop down to only 14 of those on the same driver set to the same current, you'll see the output voltage drop by 1 LED's forward voltage.

in other words, the 48v spec for your driver is a max rating, the actual voltage it puts out will depend on what it's driving.

Since you are seeing 50.6V with 14 LEDs at 950mA, we know that you are seeing a forward voltage of just over 3.6V per LED. This is pretty close to the spec for XR-E (3.7V @ 1A) so it's inline with what should be expected.

I think you are seeing why people normally drive 13 LEDs on that driver - IMHO you're running it beyond the design spec and might run in to problems. If you really want to keep 14 (or even 15) LEDs on each driver, you could turn the current down - the forward voltage of an LED will decrease as current decreases, so at some point you could get under the 48V max. Of course, you could also just remove another LED.

 

[sphil876p]

Ok, I think I understand the principle you are explaining regarding the drop in Voltage, but regarding the max voltage of the supply the spec sheet says "ELN-60-48 48V 1.3A 43.2 ~ 52.8 VDC Adjust Range." If I run the string inside of that range, will I have any problems when running close to the high end of the Manufacturer published spec? When I adjust the driver to the max voltage with no load I read 54.5V. So from what I have read this is leaving almost 4V of headroom on this specific driver. Should this not be sufficient to prevent any problems?

 

[der_wille_zur_macht]

Basically, the way it works is that your driver will put out whatever V the LEDs "need" to hit the current you have it set at. So, you could run a single LED off that driver, and you'd see it putting out around 3.7V, for instance. Add LEDs, and V output increases to keep the current constant.

The "VDC Adjust Range" is referring to using the voltage adjustment (inside the case) to modify the maximum voltage the unit can put out, similar to the "Vout" adjustment trim pot on many DC power supplies. Though, I would be really nervous about trying to adjust voltage on a constant current driver, since I don't know how the adjustment would play out. (I've never used or really looked at a constant current driver that even had any sort of voltage adjustment, so I'm just not sure how it's implemented on the mean wells.)

Also, in the end, it IS a 48V driver and you are running above that - the datasheet specs a certain % over voltage limit, and clearly you are within that (or else it would be shutting down), so in a way you're safe. But if it were me, I'd be much happier running it under specs, instead of under the max adjustment/over-voltage tolerance above spec.

 

[sphil876p]

Thanks, just trying to squeeze as much dollar to watt efficiency out of this setup as possible without causing damage to my components. Because after all, blowing up a driver would definately hurt the dollar efficiency by having to buy another. I am building this as a prototype, and with success I have approval from my comptroller(wife) to build another to light my 120 upgrade.....

 

[sphil876p]

So it is time to start soldering up the next string of LEDs.......
I had not done much soldering previously, so I had to purchase a soldering iron for this project. It is a 40 watt iron, and it has worked very well so far.

<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=PICT0289.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/PICT0289.jpg" border="0" alt="Photobucket"></a>

Here is the flux and solder that I am using to do all of the soldering...................


<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=PICT0290.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/PICT0290.jpg" border="0" alt="Photobucket"></a>

I will try to detail the soldering process I have used, because to those of us who do not have much practice with a iron this seems a little daunting

 

[sphil876p]

I start by putting a small dab of the flux on to the positive and negative pads I am going to use on all of the LEDs in the string.....

<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=PICT0299.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/PICT0299.jpg" border="0" alt="Photobucket"></a>

Then after the iron is heated up I clean the tip with a damp sponge, and quickly touch the pad with the iron and solder until a puddle of solder develops on the contact pad..........
From what I have read I believe the goal is to do this in about a 1-2 second timeframe. At first I wasnt able to get it done that quickly, but after a few it has become pretty easy for me. Every few I seem to get the tip dirty with the solder again so I clean the tip regularly........

<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=PICT0318.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/PICT0318.jpg" border="0" alt="Photobucket"></a>

 

[kcress]

MAN... That Stay-Clean better not be what I think it is or you just wrecked a bunch of LEDs...

I've never seen electronics solder paste in that kind of a can.

You should NOT need any more solder flux than what is in the core of your solder.

 

[sphil876p]

What damage will this cause, and is there any way I can clean and resolder the connections????

 

[sphil876p]

Can I just resolder to the other pad after cleaning the first???
Man I am crashing and burning now :mad2:

 

[sphil876p]

AAARRRRGGGGGG!!!!!! I like to learn my lessons the hard way :mad2: Flux Mfg specs say not recommended for electronics.........
So, mass state of panic I reheated all of the connections and removed as much of the solder as possible. I then cleaned all of the stars, and painted liquid electrical paste on all of the first connections I made.

<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=PICT0321.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/PICT0321.jpg" border="0" alt="Photobucket"></a>

I have soldered with NO ADDITIONAL FLUX to the second set of connections on the stars.

<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=PICT0322.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/PICT0322.jpg" border="0" alt="Photobucket"></a>

Moving forward as planned will start rewiring the strings together..........

 

[Monsta]

The way to connect those led's is to pick up a bit of solder with the soldering tip and transfer it on top of pre-pasted connection surface and wire. It creates clean, strong and professional looking bond and requires no multi-step soldering.

 

[kcress]

In the LED thread I detailed proper soldering technique. Here's it is lifted in its entirety:

Soldering... It's a bit of an art form. It you're an expert you could probably solder the stars with anything but a torch. But if you aren't accomplished a 'just right' soldering iron is required. Something around 25 to 40watts. The biggest problem would be one too small as then you damage what you are soldering by sitting there with the heat on, waiting, and waiting for the solder temperature to be reached. Meanwhile the device is being roasted.

You need "rosin core solder." Make absolutely sure it's not 'ACID' core solder. Acid core is solder for soldering radiators and copper pipe. The acid remains and will dissolve your electronics in short order. No-core or plain solder is also very bad as there is no cleaning action which is vital to an acceptable solder joint.

You want lead solder too - NOT "lead free".

Let your iron heat up fully. Then wet it with your rosin core solder until it's blobbed up in a wad. This lets the rosin act on the tip to clean it. Wipe this blob off on a moist sponge,(not sopping wet, just barely damp). If you have no sponge use a damp folded up paper towel.

Wipe with a very fast twirling dragging motion as you are trying to clear all the solder off the tip before you cool the tip to the point that the solder freezes again.

Apply a weee bit of solder to the tip and then immediately apply the tip to the star's pad. As soon as you apply the tip to the pad take your solder and touch it to the exact point where the tip meets the pad. You are trying to maximize heat transfer from the tip to the pad. You do this by filling all the voids with a molten metal thermal bridge. Pause for, perhaps, one or two seconds move the solder to a distant place on the pad and hold it there. When the pad heats up enough to melt the solder feed the solder in at a good clip until the pad has a large mound of solder on it.

Do the same thing to your wire if it is un-tinned. (actually do this before you do the pad!) Better(superior) would be to use only pre-tinned wire in the first place.

Now once you have your mound of solder on the star pad bring over your wire, hold it on the Star's pad. Place the tip on top of the wire. You want to reheat the pad thru the wire. When the wire sinks into the blob hold the position and watch the blob. You want the entire blob to melt again. The instant the blob has remelted remove the tip while holding the wire EXACTLY where it is. No wiggling allowed! Coffee shakes need not apply. Once the solder has refrozen move on to the next connection.

 

[dtech]

I have always done what kcress describes, is what monsta describes different?

 

[sphil876p]

<a href=showthread.php?s=&postid=15299138#post15299138 target=_blank>Originally posted</a> by Monsta
The way to connect those led's is to pick up a bit of solder with the soldering tip and transfer it on top of pre-pasted connection surface and wire. It creates clean, strong and professional looking bond and requires no multi-step soldering.

I guess he is referring to putting the correct type of flux on before heating the solder joint. I used flux that was not the correct type for electronic soldering. I assume that means it is corrosive......
So, I desoldered all of the connections, and cleaned as much of the solder off of the terminals as possible. I then resoldered all of the LEDs using the terminals that were previously unused. Hopefully this will save me the heartburn of premature LED failure due to my error.

 

[kcress]

<a href=showthread.php?s=&postid=15299138#post15299138 target=_blank>Originally posted</a> by Monsta
The way to connect those led's is to pick up a bit of solder with the soldering tip and transfer it on top of pre-pasted connection surface and wire. It creates clean, strong and professional looking bond and requires no multi-step soldering.

Picking up and transferring "a bit of solder" means you will get NO cleaning of the joint by the solder's flux core. This will result in poor "cold solder joints" unless there are absolutely no oxides on the wire or pad. The flux's 'activity' is very brief and is completely gone in about 1/2 a second. Far longer than it takes to blob-and-sob.

 

[Monsta]

I meant pre-fluxed with my pre-pasted wording...But you are absolutely right; My way of soldering requires addition of rosinflux onto all surfaces to be joined.

 

[sphil876p]

Happy Independance Day!!!!!!!!!!!!!!

<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=SSPX0157.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/SSPX0157.jpg" border="0" alt="Photobucket"></a>

 

[a1amap]

You want lead solder too - NOT "lead free".

Electronics grade solder can be "lead free" and typically lead free soldier contains Sn 97 Ag 2.5 Cu 0.5 (i.e. 97% tin, 2.5% silver and 0.5% copper). It already contains cores of "flux" which helps the molten solder to flow more easily over the joint and burn off oxides.
You will be hard pressed to find 100% lead solder and there are quality alternatives. Over the years the amount of lead has been reduced to the current levels of a max of 40% lead. Electronics solder has some lead it but the main ingredient is mostly (60%).

FYI...solder, flux and everything known to man is known to the State of California to cause cancer..

 

[kcress]

Yep. And lead less solder is horrible. It leaves an ugly cold soldered looking joint even if it's not a cold joint. It requires more heat that can damage ICs. Also without Pb the joints can be subject to tin whiskers forming over time which can result in shorts and other failures. Probably not a problem with stars.

I use Sn63Pb37 with flux to do everything electronics. The diameter is also important for most my work but for soldering stars any size is usable.

 

[sphil876p]

Wow, very busy holiday weekend :rolleye1: time for an Update:
I was able to finish most of the resoldering, and testing the first string after making the new connections. All is well so far, LEDs fired up and the numbers are reading the same as before on the multimeter.............
I tried to take some pictures to demonstrate how they look at the max setting and min setting, but the pics do not show the difference at all. All I get is giant streaming light blobs :lol:

Here is what I have wired on the sink.........

<a href="http://s173.photobucket.com/albums/w64/sphil876/reef%20pictures/?action=view&current=PICT0328.jpg" target="_blank"><img src="http://i173.photobucket.com/albums/w64/sphil876/reef%20pictures/PICT0328.jpg" border="0" alt="Photobucket"></a>

My Royal Blues will deliver tomorrow, and will get those mounted and soldered. I will post the second string meter readings and try to give some reference pics for the brightness, and width of beam etc. as soon as possible......

BTW are we taking our summer break from the Reefkeeping magazine or what?