Led lighting confusion

[Phildago]

Hey everybody,

So I'm running into some confusion here that I really need help figuring out.

I have a string of 16 420nm epileds that were listed on the product page as 350-1500mA and 3V.

At this rating I setup my leds as a 48V string using an ldd1000 to power them.

Yesterday I stumbled upon some people discussing that these leds are in fact rated wrong in the website and that they can take up to 750 mA max. And I found documentation elsewhere on the web that they are not only 750 mA max, but also run at closer to 4V (3.5-4.5) forward voltage.

Datasheet:

https://cdn.shopify.com/s/files/1/0920/1206/files/Future_Eden_Violet_3W_LED_410-420nm_Data_Sheet_1_b1b78ac0-7460-4951-9efc-7900c411ea12.pdf?4338958196253919673

Now, with all this said. I have no idea whether I'm overpowering or under powering my leds. I used a multimeter to test the voltage at different percentages of power and got a range of about 40-48 V, which is obvious that it won't go higher. However, my multimeter just wouldn't work for testing the mA output, so I have no idea what the amp output is actually.

I'm really looking for some help here on dealing with the physics of the issue. Is it possible that these leds are receiving 1000 mA from the power supply? If so, how could that be possible?

What I'm calculating is that these leds have a resistance of 6 ohm, meaning that at 3V per led, my meanwell ldd could only be passing 500 mA through the leds maximum. Am I missing something? If this is the case I could run this channel at 100% without fear of damaging my leds.

Also, please help me answer the question at hand rather than simply suggesting that I split the string into two. I know I can do that, but it would be a huge hassle, and although I will likely do this eventually, my main worry is that I don't want to be damaging my components.

 

[Phildago]

Bump

 

[Reesj]

Hi Elec. Engineer here whos using my own Chineese LED setup for my tank. ( Don't have sapce to put standard LEDs anyway)

It seems you have 3W LEDs and 16 of them. What I would do is get a LED driver rated for 3W LEDs.
LED driver should have voltage span of that covers 56V DC( For example 36-64V Driver) with 650-750 mA current rating.
Have to be carefull if its a Chineese LED drivers though as they give out wrong voltage levels. I used one for few moths before I recognise that it was giving out 280V DC where as the label says around 60-100 or so. Over heated and fried some of my LEDS.
If you can buy the LED driver, just connect it in series with all 16 LEDs and conenct the other end to your normal AC supply. If you can't lets see where we can go...

 

[oreo54]

Well.. first the LDD will throttle the voltage at th point that it "sees" 1A on the string.

Say you have a 48V power supply. Ldd drops 3V natively so output usually will TOP at about 45V.
If you measure 44V on the actual string you can assume it's getting the full 1A current.


w/out an Amp setting you can measure current using a shunt resistor (best you look it up) and voltmeter.

Looks like your power supply is outputting more than 48V so what is the real output pre-Ldd? I'm curious and is it adjustable?

Next test the LDD w/ the string disconnected to get the maximum possible voltage out of it..

At no load condition the LDD will just ramp up the voltage to it's max possible.
FORGOT to mention.. disconnect PWM wire so it's running at 100%

Reconnect the string and if it's lower than the above (no load voltage out) then it should be running at 1A..

If it's equal than a firm "maybe"..but unlikely.. to get that lucky though as the diodes heat they will require less voltage to get that 1A of current.

EDIT.. At 1A I'd agree they won't last long unless you REALLY cool them.
500mA is prob. iffy..

 

[splitting_lanes]

Hey everybody,

So I'm running into some confusion here that I really need help figuring out.

I have a string of 16 420nm epileds that were listed on the product page as 350-1500mA and 3V.

At this rating I setup my leds as a 48V string using an ldd1000 to power them.

Yesterday I stumbled upon some people discussing that these leds are in fact rated wrong in the website and that they can take up to 750 mA max. And I found documentation elsewhere on the web that they are not only 750 mA max, but also run at closer to 4V (3.5-4.5) forward voltage.

Datasheet:

https://cdn.shopify.com/s/files/1/0920/1206/files/Future_Eden_Violet_3W_LED_410-420nm_Data_Sheet_1_b1b78ac0-7460-4951-9efc-7900c411ea12.pdf?4338958196253919673

Now, with all this said. I have no idea whether I'm overpowering or under powering my leds. I used a multimeter to test the voltage at different percentages of power and got a range of about 40-48 V, which is obvious that it won't go higher. However, my multimeter just wouldn't work for testing the mA output, so I have no idea what the amp output is actually.

I'm really looking for some help here on dealing with the physics of the issue. Is it possible that these leds are receiving 1000 mA from the power supply? If so, how could that be possible?

What I'm calculating is that these leds have a resistance of 6 ohm, meaning that at 3V per led, my meanwell ldd could only be passing 500 mA through the leds maximum. Am I missing something? If this is the case I could run this channel at 100% without fear of damaging my leds.

Also, please help me answer the question at hand rather than simply suggesting that I split the string into two. I know I can do that, but it would be a huge hassle, and although I will likely do this eventually, my main worry is that I don't want to be damaging my components.

Just some general LED guidance. It is ok to under power them, if you have enough voltage to turn them on, you have plenty of voltage.

current is what determines brightness, and temperature of the led. Leds die from too much heat, so as long as you can dissipate the heat, you can push current through them.

the nominal current rating on you leds are with a nominal heat sink (most likely).

if the heat sink is too hot to touch, then your leds probably won’t last long

 

[Phildago]

Well.. first the LDD will throttle the voltage at th point that it "sees" 1A on the string.

Say you have a 48V power supply. Ldd drops 3V natively so output usually will TOP at about 45V.
If you measure 44V on the actual string you can assume it's getting the full 1A current.


w/out an Amp setting you can measure current using a shunt resistor (best you look it up) and voltmeter.

Looks like your power supply is outputting more than 48V so what is the real output pre-Ldd? I'm curious and is it adjustable?

Next test the LDD w/ the string disconnected to get the maximum possible voltage out of it..

At no load condition the LDD will just ramp up the voltage to it's max possible.
FORGOT to mention.. disconnect PWM wire so it's running at 100%

Reconnect the string and if it's lower than the above (no load voltage out) then it should be running at 1A..

If it's equal than a firm "maybe"..but unlikely.. to get that lucky though as the diodes heat they will require less voltage to get that 1A of current.

EDIT.. At 1A I'd agree they won't last long unless you REALLY cool them.
500mA is prob. iffy..

So here's the question then. How can I assume that it's running at 1000 mA when I don't have any extra voltage to pull from?

To me this sounds like the driver would need to break the laws of physics in order to produce the necessary current. If I was inputting 56 volts and it maxed out at 48 I'd be comfortable making that assumption, however I'm running it at max and it's maxed out so there's plenty of room to assume that it is not reaching the full power of the minimum 3.5 v/led that they are rated for

 

[splitting_lanes]

So here's the question then. How can I assume that it's running at 1000 mA when I don't have any extra voltage to pull from?

To me this sounds like the driver would need to break the laws of physics in order to produce the necessary current. If I was inputting 56 volts and it maxed out at 48 I'd be comfortable making that assumption, however I'm running it at max and it's maxed out so there's plenty of room to assume that it is not reaching the full power of the minimum 3.5 v/led that they are rated for

If they turn on, you have enough voltage.

you’ll need to measure current to find out if you’re push 1000ma through them.

 

[Phildago]

If they turn on, you have enough voltage.

you’ll need to measure current to find out if you’re push 1000ma through them.

Well I know I have enough voltage to run them up to 500 mA, but since the current is directly proportional to voltage applied chances are the ldd isn't somehow doing voodoo. If there's something in missing please help me follow along.

 

[oreo54]

So here's the question then. How can I assume that it's running at 1000 mA when I don't have any extra voltage to pull from?

You can't my point above..
LDD senses current and ajt voltage up till it sees it's set point..
If you are maxing chances are it's not getting to 1000mA

If I was inputting 56 volts and it maxed out at 48 I'd be comfortable making that assumption, however I'm running it at max and it's maxed out so there's plenty of room to assume that it is not reaching the full power of the minimum 3.5 v/led that they are rated for

IF anywhere close to this chart (no guarantee) at 3V you're pulling 190mA-ish

You'd need 67V out to hit 1000mA..(16 X 4.2V)
Use a jumper wire and take off one diode at a time till you get a voltage drop..making sure you aren't staring at them..
Then you will know the voltage needed to get 1000mA...Should be about 11.diodes..

 

[Phildago]

You can't my point above..
LDD senses current and ajt voltage up till it sees it's set point..
If you are maxing chances are it's not getting to 1000mA



IF anywhere close to this chart (no guarantee) at 3V you're pulling 190mA-ish

You'd need 67V out to hit 1000mA..(16 X 4.2V)
Use a jumper wire and take off one diode at a time till you get a voltage drop..making sure you aren't staring at them..
Then you will know the voltage needed to get 1000mA...Should be about 11...

Thank you so much for this info and chart. It's exactly what I needed. So, im safe running this with my ldd 1000 for now as long as I keep them cool.

When I get a chance I'm going to use my led tester to test diode voltage officially and report back later. If not for my issue at least for others to reference.

 

[Phildago]

I tested the absolute minimum forward voltage and came up with 2.6V, but since I don't have lab grade equipment I feel that the plot from the datasheet is reliable for the product that I received.

 

[oreo54]

I tested the absolute minimum forward voltage and came up with 2.6V, but since I don't have lab grade equipment I feel that the plot from the datasheet is reliable for the product that I received.

Prob. don't have to worry too much about cooling.. The diodes will never draw anywhere near 1000mA.. or even 500mA IF the chart and your calcs are right..

@ 100mA you will be around 2.7V
175mA for 16 @ 3V..

 

[Phildago]

Yeah, that does seem to be about all I'm going to get out of it. Which is fine for now, my par values have been great since I upgraded and the tank looks great.

I ordered a few ldd 500s, and since that will likely take a few weeks to come in I can plan how to reorganize the wiring and have it ready to go all at once. I'll likely split it into two strings of 8 and either run them on ldd 700s if I can spare, or even 1000s which I have extra of and just never crank it up over 70%.

Thanks for helping me figure this out. Now I feel confident that even if I use a more powerful driver, I can systematically test the voltage and compare to the datasheet to make sure that everything is running within the defined parameters.

 

[oreo54]

If you split the string into 2 parallel sections of 8 each you need zero new parts..
Each branch will run at 500mA.....

Now there are some catches to this and THE least one should do is fuse each branch w/ a 750mA fuse..
Ideally you would run a current balancing circuit..

Normally you don't want the drivers running "un-regulated" so to speak..
Standard operating proceedure for these diodes would be to not exceed 500mA and preferably less if you want to squeeze a longer life out of them.

 

[Phildago]

If you split the string into 2 parallel sections of 8 each you need zero new parts..
Each branch will run at 500mA.....

Now there are some catches to this and THE least one should do is fuse each branch w/ a 750mA fuse..
Ideally you would run a current balancing circuit..

Normally you don't want the drivers running "un-regulated" so to speak..
Standard operating proceedure for these diodes would be to not exceed 500mA and preferably less if you want to squeeze a longer life out of them.

I'll keep that in mind. Right now I'm actually running my white channel similarly, just without the Fuse. It works great, but I'm afraid of a mishap occurring in the future... I guess the Fuse would solve that issue though. It would've been much cheaper too.

 

[Reesj]

If they turn on, you have enough voltage.

you’ll need to measure current to find out if you’re push 1000ma through them.

This is not true. You can have a 3.5v LED run around 2V even. It will produce lower amount of light and will be operating below its optimal condition. Furthermore, this is most certainly lower the life span of the LED. Not as much as having a larger curretn flowing throught it but it will certainly effect the LED.

To coem back to to OP, I have already given you the answer how you can do the wiring. Its very simple process when you get hold of a LED driver which I'm sure you can find.

 

[Reesj]

If you split the string into 2 parallel sections of 8 each you need zero new parts..
Each branch will run at 500mA.....

Now there are some catches to this and THE least one should do is fuse each branch w/ a 750mA fuse..
Ideally you would run a current balancing circuit..

Normally you don't want the drivers running "un-regulated" so to speak..
Standard operating proceedure for these diodes would be to not exceed 500mA and preferably less if you want to squeeze a longer life out of them.

I would personally not run a below 500 mA for a 3W led rated at 750 mA. That would produce a lot lower light effect and you will not get as much of a life span running it that low. If you are worried about the life span that seriously as I have mentioned you can go around 650mA.

 

[Phildago]

I would personally not run a below 500 mA for a 3W led rated at 750 mA. That would produce a lot lower light effect and you will not get as much of a life span running it that low. If you are worried about the life span that seriously as I have mentioned you can go around 650mA.

Im using ldds and double checking all my voltages and what not. My main issues were with verifying that the datasheet was correct because the original parameters that the seller had supplied were way off.

I have no idea how to check the amperage on these leds though. When I put my multimeter in series with them I get nothing. The lights don't turn on and there's no current. So I've been trying to assess based off the output voltage for the channel.

As far as getting the most out of them, I'm going to have to pick and choose my battles with these. I have 5 ldd1000s, 2 ldd 700, 3 ldd 300 and 5 ldd 500. I'm going to play around with my spread sheet and recheck to see where I can make the adjustments, but I will try to make it so I can dedicated those two 700s to the 420s and run them around 650 MA.

 

[splitting_lanes]

This is not true. You can have a 3.5v LED run around 2V even. It will produce lower amount of light and will be operating below its optimal condition. Furthermore, this is most certainly lower the life span of the LED. Not as much as having a larger curretn flowing throught it but it will certainly effect the LED.

I have not experimented with under voltage situations with leds. Thanks for the information

 

[Reesj]

Im using ldds and double checking all my voltages and what not. My main issues were with verifying that the datasheet was correct because the original parameters that the seller had supplied were way off.

I have no idea how to check the amperage on these leds though. When I put my multimeter in series with them I get nothing. The lights don't turn on and there's no current. So I've been trying to assess based off the output voltage for the channel.

As far as getting the most out of them, I'm going to have to pick and choose my battles with these. I have 5 ldd1000s, 2 ldd 700, 3 ldd 300 and 5 ldd 500. I'm going to play around with my spread sheet and recheck to see where I can make the adjustments, but I will try to make it so I can dedicated those two 700s to the 420s and run them around 650 MA.

It does not matter if the data sheet is absolutely correct to the decimal point. Generally 3W LEd that are not Red operate around 3.5V with 750mA current range. You can not check the current at the moment as it does not have a sufficent voltage across the LED, from what I can understand.
Anwyay, you are not trying to tackle the problem properly. Get a way to produce 56V (50-60) DC independedntly and if you want check the amper range to make sure.
IF NOT get a LED Driver, with the spec I have already mentioned. I seriously don't undestand why you would not get a LED driver that should be quite cheap and easy way to solve this problem....