LED Fixture Build --Kcress--

Dirland,

Check the data sheet. I am not sure you can run 8 LEDs. IIRC the minimum voltage is 24 volts so that would be 3 volts per LED. Which LEDs are these?
 
I am just a little confused now, Mike from rapid led told me that to run 2 strings of 8 they would only run at 650 mA. The driver is 24-48v and 1.3a.

kcress you ran 2 strings of 12 of a driver with 1.3a and had higher mA?

Why will my 2 strings of 8 only run at 650 mA?
 
I am just a little confused now, Mike from rapid led told me that to run 2 strings of 8 they would only run at 650 mA. The driver is 24-48v and 1.3a.

kcress you ran 2 strings of 12 of a driver with 1.3a and had higher mA?

Why will my 2 strings of 8 only run at 650 mA?

What you're not getting is that there is a minimum number of LEDs you can drive with most drivers. You are risking hitting that limit with only 8 LEDs.

48D can only control the current down to 24V.
8LEDs x 3V/LED = 24V. The very bottom of the limit. You should consider using a few more in your strings. Your 8 might work(it depends on the LEDs you buy having high enough Vfs, 9 would work with more assurance.

Yes 650mA is the conservative drive level. You could probably adjust up to 700mA x2 as long as your driver has good air flow around it.
 
I would guess he was able to run his lights under the rated wattage of the unit probably under the rated voltage.

If you're running both strings at 650ma and voltage is 48vdc then that would be 650 x 2 for 1.3 amp x 48 volts = 62.4 watts the driver you're using is rated for 62.5 watts.
 
So I was thinking about just adding another driver for 3 total and just do 11 leds per driver.
Does this sound like a better way to go?
 
Picking up were we left off.
I want to go back a bit and show the fire-up process of a parallel string build.

Once you have everything wired up you need to check your wiring. You should really NEVER turn on a build and have parts of strings not correctly go on. That's really bad form. So the first thing you do is use a DMM with a diode test. Set it to DIODE and run down every single LED. Touch the solder blobs not the other pads. We don't care about the other pads, we only care about the ones we actually used. (Sorry for the hazy pictures the camera focused on my fingers!!)

Here I probe a blue LED in the proper direction and you can see it lights up. If it doesn't you have a problem. You could also do this with the two AA batteries method.

0yq77h2h3p.jpg


Next I move one probe to the chassis leaving the other in place. If I botched something that shorted the other lead to the chassis the LED will light up again - incorrectly.

erdx6u0nh1.jpg


Then I go back across the LED to light it up again and swap the opposite probe to the chassis to check for a short on the other side of the LED. Do this on every single LED on your build before powering up. It takes only a few minutes and will prevent any ugly, expensive, surprises.

ragjy5zfp0.jpg


That done we can move on to adjusting the driver. I turn the current limit allllll the way down. Sometimes they ship them all the way up. If they do this and your strings are badly balanced you could toast one. If you turn it all the way down you likely won't toast anything even with horribly mismatched strings.

aefpmsf5re.jpg


Also take the time to turn the voltage limit all the way down too. This is a safety thing that can also save you in a mess up. Large currents tend to require higher voltages. Turning the voltage limit down limits the current that can occur through a secondary aspect.

9hv1q5gizv.jpg
 
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