# Driving ten 3w chinese LEDs



## jotape65 (Sep 14, 2010)

I purchase ten 3W leds from ebay, which I am trying to drive in series using the "Waterproof 320mA 20W Power Constant Current Source LED Driver (85~265V)" from dealextreme. It is not working. The leds are working as I tested them individually. Not sure If I received a defective driver or I am missing something. Anyone using a similar setup?

Thanks,
Jaime


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## redfishsc (Aug 29, 2010)

Need more info, and perhaps a pic of possible. 

You are probably not up to the minimum voltage requirements for this driver--- you are on the verge. 


Those LEDs usually have a 3.7v forward voltage, but that's at a higher current. At 320mA it's possible (though not likely) that their combined voltage is lower than 35v. It should still light them up, I've seen other drivers light up stuff under lower loads before, it's just rough on the LEDs. 



Try them again without the LEDs attached but test the voltage across the driver outputs (+ and -). Don't let the wires touch obviously . Just check with the multimeter terminals.


If it reads anything between 35 and 65 (give or take; this is the drivers voltage range) then the driver is likely OK. 


If the LEDs are working individually, and the driver is working, you may have a bad solder joint or a solder joint that's grounding out. 

Pics will help


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## Zareth (Dec 13, 2010)

Under powering LED's isn't "rough" on them, they will actually last longer. 
I'm sure you know LED's don't work if they're hooked up backwards (+ on - instead of + on +)
First make sure you have them all in the correct orientation. 

I don't know how that driver works but I'm assuming it's hooked up to 120v wall current? 
Make sure its hooked up to the correct side of the driver (input not output) 
Also if you attempted to test one led with the driver its possible the current was too strong, due to there not being enough resistance from multiple LEDs or a resistor, that you fried the driver. 
Either way, if these are the Star LEDs they have multiple connections so its easier to make a mistake in the wiring, just double check everything a few times and make sure your DC current is all flowing in the right direction to be in series.
I cant remember if the actual star of the led needs to be grounded, if your using star leds that is, so look into that as well.


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## redfishsc (Aug 29, 2010)

Zareth said:


> Under powering LED's isn't "rough" on them, they will actually last longer.




If this was in response to my suggestions, I didn't say he was underpowering them. I said that he is probably not up to the minimum voltage requirements for this driver. 

If you don't give this driver enough LEDs to power, it will actually give them too much voltage. 


At 320mA, an LED may only have a forward voltage of 3.0 or 3.3, and his driver is going to put out at least 35v, which isn't good for 10 of these LEDs.

I can't say that for sure since I don't know the forward voltage of these LEDs at 320mA. 


But you're right about the drive current- running them at 320mA will help them run longer for sure. Also keeps heat sink cooler (you can use a smaller heatsink). You just have to have enough of them to get the PAR numbers you want.




Zareth said:


> Also if you attempted to test one led with the driver its possible the current was too strong, due to there not being enough resistance from multiple LEDs or a resistor, that you fried the driver.



A good point to remember (never test 1 LED with a driver unless the driver can handle low voltage loads). 

However, it would have more likely toasted the LED instead of the driver. A multimeter check for voltage on the driver will answer that question quickly.

Also, what does the damage when testing 1 LED isn't the current (they are pre-set at their rated current)--- it's the voltage. In this case it would hit a single LED with 35v and fry it instantly (unfortunately I did learn that the hard way lol).


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## jotape65 (Sep 14, 2010)

Thanks for the suggestions!

I tested the LEDs using a 12 volt supply across different sets of 3 LEDs series with a 25 ohm resistor (500mA current) and they all lit up, so I know wiring is correct.

Chinese LEDs I got are spec with forward voltage of 3.4V to 3.6V, but reality might be otherwise.

I fetch my meter from the office and tested the constant current driver open and with a 120 ohm load (should of read 38.4V) and in both cases the voltage across the output leads was zero. It appears I have a bumm driver, an that's a hassle since it took a couple of weeks to come from China.

I guess there is no magic involved, just Ohm's law.


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## [email protected] (Jul 17, 2008)

Statistronics is now selling some drivers. My order from them took 17 days. I quit counting at 35 days for my order from Deal Extreme. Product was fine and communications was fine, but twice as long for delivery. 

http://www.satistronics.com/Wholesale-led-lamp-lightings-driver-for-leds_c1038


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## jotape65 (Sep 14, 2010)

Thanks dbossman. I think statistronics 300mA driver might do the job.


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## redfishsc (Aug 29, 2010)

[email protected] said:


> Statistronics is now selling some drivers. My order from them took 17 days. I quit counting at 35 days for my order from Deal Extreme. Product was fine and communications was fine, but twice as long for delivery.
> 
> http://www.satistronics.com/Wholesale-led-lamp-lightings-driver-for-leds_c1038




Satistronics is decent, I have several of their LED products. But you have to watch very carefully on their datasheets. Their data is somewhat legendary for being inaccurate. 


I fried a $14 20-watt LED from them because they gave a false voltage on their datasheet. When I brought it to their attention and asked for a refund, they changed the datasheet jpg image to a correct one, and then played stupid with me. Literally told me "the data is correct, look again!". Bull. 

I showed them a screen shot of the image (same LED cross-listed on another part of their site) with the old, incorrect datasheet, and they refunded my money (among saying other things to me lol). 


I also have a driver that I ordered that was supposed to be a 10v, 900mA driver, and it arrived as a 12v, 1,000mA driver......... not a big deal and I'm using it right now, and works great... but it's not what I actually ordered.


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## redfishsc (Aug 29, 2010)

It's actually STILL wrong on their main page. See this image? Does it say 16-20v for the forward voltage? If you do that, you'll cook them. 

I have one in my possession right now (I fried one of the two I ordered). It only has a forward voltage of 12.5 at 700mA, I've checked it on a Buckpuck. If you put 16-20v on it, it's toast. 











The same LED is cross listed on their SatisLED site and it shows the correct approximate voltage range, 13-15v.

http://www.satisled.com/20w-high-po...ue-white-warm-white-yellow-for-choice_p3.html


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## jotape65 (Sep 14, 2010)

Found this cool online resistor led calculator:

http://led.linear1.org/led.wiz

I think I will use a constant voltage supply instead of a constant current driver.


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## [email protected] (Jul 17, 2008)

redfishsc said:


> Satistronics is decent, I have several of their LED products. But you have to watch very carefully on their datasheets. Their data is somewhat legendary for being inaccurate.


Ah, knowledge. That's where you went wrong. I have only a basic understanding of electronics so I can't use Statistronics data sheets. I also have a problem when it comes to colors. I didn't know other countries used different colors standards for electronics. 
Statistronics sent me drivers with two pink leads at one end and a white and pink at the other end. It took a magnifying glass and some time to figure out white was negative, pink was positive and paired pink was AC.


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## redfishsc (Aug 29, 2010)

Did the AC-in have polarity? Every LED driver I've ever used (about 6 different types, admittedly not that much) had clearly marked polarity for AC in.


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## redfishsc (Aug 29, 2010)

BTW if you'd like some clarification on what the datasheets are telling you (or, are supposed to be telling you) then shoot me a pm and I can explain them for you.


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## [email protected] (Jul 17, 2008)

redfishsc said:


> Did the AC-in have polarity? Every LED driver I've ever used (about 6 different types, admittedly not that much) had clearly marked polarity for AC in.


Almost no markings at all on the driver. I finally found a + on the circuit board, between the pink lead, the transformer, and the capacitor. I assumed that meant DC positive and wired it up and tested it at the end of a six foot AC power cord in case anything popped or burned up. My glasses are safety grade polycarbonate so I had that side of the experiment covered.


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