Help with drivers

knap_123 · Aug 14, 2017

I bought some used leds with 24 leds on a heatsink. 8nw, 8rb, 8b
I want to use meanwell dc/dc ldd-h drivers. I'd like to use 4 total. I have 2 identical heatsinks. I tried each led and they work. I tried all blues 24 total. With 1 driver and nothing. I'm sure my wall wort 12v is to small. What do I need to do?

Brew12 · Aug 15, 2017

knap_123 said:
I bought some used leds with 24 leds on a heatsink. 8nw, 8rb, 8b
I want to use meanwell dc/dc ldd-h drivers. I'd like to use 4 total. I have 2 identical heatsinks. I tried each led and they work. I tried all blues 24 total. With 1 driver and nothing. I'm sure my wall wort 12v is to small. What do I need to do?

You need to do some math. To make this work you need to know the voltage drop and power consumption of each LED and match the parallel/series sets to the ratings of the driver.

knap_123 · Aug 15, 2017

Need at least 40-48v input , correct? The leds are old and no way to get any info on them. So I'm just guessing on there forward voltage.

Brew12 · Aug 15, 2017

knap_123 said:
Need at least 40-48v input , correct? The leds are old and no way to get any info on them. So I'm just guessing on there forward voltage.

I would guess so, if you want them all in series. Or you can use a lower voltage and create 3 or 4 parallel/series groups if the driver has enough power.

knap_123 · Aug 15, 2017

Yes, 4 strings of 12 leds. Blues on 2 stings, whites on the other 2. In series each on a ldd-h 1000ma driver.

knap_123 · Aug 15, 2017

Will 1 48v powersupply drive all the leds. Or do you need 4 seperate power supplies?

Brew12 · Aug 15, 2017

knap_123 said:
Will 1 48v powersupply drive all the leds. Or do you need 4 seperate power supplies?

If I understand what you are trying to do, a single 48V power supply should work as long as it is rated for at least a 4 amp output.

knap_123 · Aug 15, 2017

Wouald these be easier?

Brew12 · Aug 15, 2017

You should be able to make either option work. Its just a matter of sizing the driver to the LED's. It may not work, or you may not get a full range of brightness, if the driver isn't sized to the LED's you are attaching. You may need to remove or add an LED or two to get the proper combination of voltage and current.

knap_123 · Aug 15, 2017

Ok, I tried 6 leds at 24fv. And they lit up! I guess 12 wasn't my lucky #. I'll do strings of 6.
That will require more drivers than I wanted.

Brew12 · Aug 15, 2017

knap_123 said:
Ok, I tried 6 leds at 24fv. And they lit up! I guess 12 wasn't my lucky #. I'll do strings of 6.
That will require more drivers than I wanted.

Try adding more to the string and try dimming them through a range. You may find that if you only have 6 they will light up but burn out quickly from overvoltage.

Brew12 · Aug 15, 2017

Or, if you have a voltmeter, try taking a voltage reading across a lit LED. Its tough since you don't have the data but for the blue LED's I would expect around 3 VDC across them. If you have 4VDC-6VDC they will show very bright but will burn out quickly so you will want to add more to the series change.

If 6 in series works, you can try to add the other 6 in parallel. That way you can still get the same voltage drop across each LED and power 12 off the driver.

knap_123 · Aug 16, 2017

Ok, parallel is +++++ ------- not +-+-+- correct?

Brew12 · Aug 16, 2017

knap_123 said:
Ok, parallel is +++++ ------- not +-+-+- correct?

Correct.
To create 2 parallel groups of 6 in series you would duplicate what you already have and only connect them on each end.
+-+-+-+-+-+-
ps+ -ps
+-+-+-+-+-+-

Hope that makes sense.

Donovan Joannes · Aug 16, 2017

Be careful when hooking up a series of LED without knowing the Vf and max current of each LED. This is very true if the power supply is not a LED driver (normal dc supply). You must hook up a current limiter resistor (properly sized) so that the LED doesn't failed too soon (sometimes instantly) due to over current.