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Discussion Starter · #1 ·
Hi all,
I bought 4 of the meanwell HLG-240-48b drivers and I finally have 2 of them wired up to my LED array. I have 1 running 6 strings of 11 (66) XP-G cool whites and the other driver running 5 strings of 12 XP-E royal blues (60). This is half my led array. I have the reefled dimming kit (2 pots in the case). I have these wired up and when I put a meter on the pot outputs, I can see the volts go from 1 - 10, I also see the voltage change on the wire that I am running to the blue (+) wire of the driver. When I turn the pots up and down, the LEDs get brighter and dimmer but my concern is that each string is running about 600 to 1000 mA and I can not get them to turn down any lower than 600. I know I need to balance my strings but my concern is that these do not dial down to the 200 or 300 mA range. I do not think I will ever want to run these up in the 800 - 1000 mA range. Can anyone throw me any suggestions on why they will not dim below 600mA?

Here is the basis for my parallel wiring layout. IGNORE THE RESISTORS in these diagrams. I only have a 1 OHM 5 watt resitor per stinrg



 

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Discussion Starter · #2 ·
a little moew info

I have my driver leads running to wiring blocks. wire in , fuse, 1ohm 3 watt resistor and then out to the first LED of the string. I measured vf across the resistors and they are all over the board, 600, 800, 800+, etc. I know I need to start swapping some LEDs to get the strings balanced but it just seems odd that even when these are dialed all the way down, the vf across the resitors is never lower than 600 mA.

I have not measured from first LED to last LED and I have not measured the vf of each LED yet. I did not want to let them run that high and that out of balaance for long, plus it is almost impossible to work on them at 600 mA. I could post some pics of the wiring and such, just wondering if there may be something I missed inthe build. internal pot on the driver, etc.?
 

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Discussion Starter · #4 ·
are you dialing down your pot all the way? or do you hit a point and the led's just go out?
The LEDs can't go out with the dimmer, the lowest the driver could go to would be 10% at 1v. My issue is that even with the POT turned down, they driver is outting out around 600 mA per string. I am going to get some new reading and pics posted up by Thursday evening or sooner.
 

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well if you only have a 1 ohm resistor then the current is going to run high you need a larger resister you are feeding the led's too many volts. that is why you are having the problem i want to say you need 10x the resistance (as your diagrams say may be go a little higher) to be where you want to be add resistance and you will be able to down the current the higher the amount of voltage the the current will rise exponentially because in an led the resistance goes down as the voltage goes up allowing more current to flow more easily faster. the pot can not compensate for that much resistance it seems so you could get a different pot or a larger resistor or add 1 or 2 led's to your string accordingly.

it dose seem you need to balance out your strings though.

that's just a stab at it now that i noticed the 1 ohm resistor on the strings not 10 and 18 sorry i missed that before

Here is the basis for my parallel wiring layout. IGNORE THE RESISTORS in these diagrams. I only have a 1 OHM 5 watt resitor per stinrg
 

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Discussion Starter · #6 ·
well if you only have a 1 ohm resistor then the current is going to run high you need a larger resister you are feeding the led's too many volts. that is why you are having the problem i want to say you need 10x the resistance (as your diagrams say may be go a little higher) to be where you want to be add resistance and you will be able to down the current the higher the amount of voltage the the current will rise exponentially because in an led the resistance goes down as the voltage goes up allowing more current to flow more easily faster. the pot can not compensate for that much resistance it seems so you could get a different pot or a larger resistor or add 1 or 2 led's to your string accordingly.

it dose seem you need to balance out your strings though.

that's just a stab at it now that i noticed the 1 ohm resistor on the strings not 10 and 18 sorry i missed that before
Thanks for the reply, I am not an expert at this but I did research this for almost a year before starting this.

According to all the writeup and advice from several others, the only thing the resistors are used for is a way to measure the vf of each string, hence the reason to use a 1 ohm.

Based on the drivers, for the blues, if I have 48v/3.4 LED vf = 14.11 or 14 LEDs per string. Running them at 800 mA would draw about 4A from the driver. If I ran them at 1000 mA they would draw 5A (The max on the driver is 5A)

Based on the drivers, for the whites, if I have 48v/3.2 LED vf = 15 LEDs per string. Running them at 800 mA would draw about 4.8A from the driver. If I ran them at 1000 mA they would draw over 5A (The max on the driver is 5A)

So I am not sure why the resistors are an issue on the whites. For the blues, it looks like I could run 2 more on each string, I now have 12 on each string and I could go 1. But I have to look at the vf of each LED to see how close to 3.4 v thay are running in order to makean accurate calculation. Since these have dimming POTs why would I need to add resistors? I would rather not just burn up excess energy, I want to put it to work.
 

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although the driver is current driven the laws of electricity still apply i would agree with you but your math is correct i would have a string of 14 and 15 led's depending on the colors. with the pot you are just able to manipulate the voltage through the strings with will naturally raise or lower the current and to measure Vf all you need to do is put the contacts of your volt meter across any load it will tell you the vf

edit: put the leads on either side of a load to find out the voltage forward on that/those load/'s

the resistor has to have a voltage drop = to what ever the number of led's you are trying to eliminate(as well as watt dissipation = pita easier to use an led or 2) from your strings if you have the led's you can just add them keep in mind as the voltage across each led increases the current will exponentially increase so having just 2 loads missing will drastically increase the amount of current going through your led's i would make my strings 14 long and 15 long to control the voltage at max then your pot(witch is a variable resistor) will be better able to dim your led's

i hope this helps
 
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