# 72w LED Light Bar Repair



## Angelofhevn (Feb 1, 2015)

Hello and greetings from finland!
I ordered long time a go a 72w, 24 High Power Led Bar that can be used from 10 ish volts to 30 volts.
recently the leds stopped working and now theres just 6/24 left that lights up. I opened it up and found out that it was cheapely made with slim components and no capacitors.. The leds were connected in series so the power draw was 9watts for the 3 leds and the controller was a 6 pin chip with "PT4115 12962C", just of 2 of therse little guys were alive of a total of 8. Some of them was blown off the board and left a hole and some of them were melted.
Now i did some research and found out that they are indeed poorly made but i still want it working again. I found that LM317 could be used to power 1 of therse leds but sence they are connected 3 in series that was not the best idea, because of the cost and so on. I found some "Led Drivers" on ebay that was rated for 1x3w,2x3w and 3x3w leds but they seemed to be built the same way the original was but without the capasitor. there was so much different ones with different "specs" but all looked the same. here was the one i found. http://www.ebay.com/itm/5pcs-LED-Hi...ing_Parts_and_Accessories&hash=item3cd65590af
Does anyone have a idea how i could power therse leds again without spending so much Euros on expensive drivers. If you know please let me know. Pictures are bellow.

Pictures will be uploaded in a few Minutes.


----------



## Angelofhevn (Feb 1, 2015)

I did not find any Edit button so sorry for double post.
Heres the link to my Photobucket album with pictures of the Lightbar and the components inside
http://s79.photobucket.com/user/ric7501/library/72w led bar?sort=3&page=1


----------



## Microa (Feb 1, 2015)

AT the top of your photo, the brown colour component close to the diode is a Multi-Layer-Ceramic-Capacitor which performs better than the E-Cap in high temperature environment.


----------



## DIWdiver (Feb 1, 2015)

I looked at the datasheet for that chip, and it should handle that application pretty well. My guess is that there's no transient suppressor on the board, and the nasty electrical environment has successively trashed one after another. If that's true, then they severely compromised the design for want of a 3 cent part.

Before you blow the rest of them, I'd put a transient suppressor across the power input. Something like this is probably overkill, but not too expensive. http://www.digikey.com/product-detail/en/3KP24A-TP/3KP24A-TPMSCT-ND/1960102

For repairing the board, you have three choices:
1. Get some of those parts, and replace them on the board. Unfortunately, it looks like your board may be damaged pretty badly, making this impractical.
2. Get some cheap drivers, and hope for the best.
3 Get a more expensive driver or two that could handle multiple strings of LEDs.

No matter what you do, a transient suppressor is critically important. If your drivers don't include them, you should add one at the power input to the board.


----------



## Angelofhevn (Feb 2, 2015)

Can someone send a example of a decent driver for the leds? I still dont want any super fancy stuff, but anything that should last some time and having 12v input. If possible a driver that can power all the leds on the same time  Thanks for all help you have allready gave me :laughing: I had no idea that the brown SMD was a Capacitor


----------



## Angelofhevn (Feb 2, 2015)

Well after hours of searching i found a few drivers rated at around 100w with 12v inputs. My concern is that i cant hook up the leds easily because the leds are 3v each if im right so 3 of them in series is around 9v, and then 8 connected in paralell? heres a picture of what im thinking but is it even possible or should i have a driver that has 8 channels and then wiring each channel to 3pcs inn series? Anyway i got a new picture in the Photobucket album that show how i meant to connect the leds. Im not sure if it can be wired like that  http://s79.photobucket.com/user/ric7501/library/72w led bar?sort=3&page=1
I found a few drivers on ebay and heres the links to them.
http://www.ebay.com/itm/100W-DC12V-...673?pt=LH_DefaultDomain_0&hash=item566af4a241
http://www.ebay.com/itm/DC-DC-const...760?pt=LH_DefaultDomain_0&hash=item4ae42c5608
Thanks.


----------



## DIWdiver (Feb 2, 2015)

Yes, you can wire them like that.

But you'd need an 8A driver to get to full power. With the drivers you found, you could run 3 strings or 2 strings to full power on each driver, respectively.

There's some chance the strings won't share current equally, but that's usually pretty minimal if the array is all from the same batch.


----------



## Microa (Feb 2, 2015)

Yes, you can wire the multiple strings of LED like that.
The drivers you found don't have enough current to drive all the 8 channels of the LED strings as the original design of the light bar. Each LED string was designed to drive at about 0.56A.(0.1V current sense threshold voltage of the PT4115 / R180 sense resister = 0.56A LED driven current) You need 4.48A to drive all the 8 channels. Please note the LED is current driven not by voltage.


----------



## Angelofhevn (Feb 2, 2015)

I guess i will continue searching


----------



## Angelofhevn (Feb 3, 2015)

i found 2 more drivers that can handle 6A and have wide input voltages. 
http://ebay.com/itm/181566791416?nav=SEARCH
http://ebay.com/itm/311164200896?nav=SEARCH Is anyone of therse capable of powering them? I really started to look at the more expencive one but the cheaper looks to be slimmer and easier to put in a enclosure.


----------



## DIWdiver (Feb 3, 2015)

Microa said:


> R180 sense resister...



Good Catch! I had in mind that they were being driven at 1A, so I saw the appropriate R100 resistor. They are actually R180.

Running 1A in each string, however you do it, would be a serious increase in power. Quite possibly dangerous to the LEDs.


----------



## DIWdiver (Feb 3, 2015)

Angelofhevn said:


> i found 2 more drivers that can handle 6A and have wide input voltages.
> http://ebay.com/itm/181566791416?nav=SEARCH
> http://ebay.com/itm/311164200896?nav=SEARCH Is anyone of therse capable of powering them? I really started to look at the more expencive one but the cheaper looks to be slimmer and easier to put in a enclosure.



Either of those might work. Or not.

Those are buck regulators, which means the output voltage will always be lower than the input voltage.

So say your LED string is 9V, and you have a 20V input. Should work just fine. Now say you start reducing the input voltage. At some point, the output voltage will begin to drop. Right at this point, just where the output begins to drop, the difference between input and output voltages is called the 'dropout' voltage'. The output voltage can never be higher than the input voltage minus the dropout voltage. The price is higher, but you can depend on it being a quality product.

Based on the specs of both of those regulators, it looks like the dropout voltage could be as high as 4V for both of them.

Say it is. If you are in a vehicle with the engine running, the input voltage is probably around 13.8V. The driver could then produce an output voltage of 13.8-4 = 9.8V. If your LED voltage is 9.0V, everything is fine. But say you shut off the engine and the voltage drops to 12.8V. Now the max output voltage is 12.8-4 = 8.8V. That means the LEDs would be underdriven, and would dim.

Now 4V is pretty high for a dropout voltage. I'm not saying those drivers have a 4V dropout voltage. But they don't say what it is, and the other specs make it look like it could be that high.

Taskled makes excellent drivers, and his H6CC should do this job handily. I don't specifically see dropout voltage mentioned, but in the data sheet there's a plot with a point driving 5A at 10.5V out, about 11V in, suggesting a dropout voltage well under 1V.


----------



## Microa (Feb 3, 2015)

Thank DIWdiver have said to the point for me.

I guessed that those 3W LEDs of your light bar are China Made or Chinese assembled. Their recommended maximum driving current is 700mA and their typical forward voltage are between 3.2V to 3.6V. You need to find a low dropout buck driver.


----------



## Angelofhevn (Feb 4, 2015)

I think the Chinese made driver above will suit my use. gonna mount it on my Volvo 940 and hook it up with a relay to the battery and controll it from high/low beam relay so the bar just lights up on high beam. The car will be running all time when the bar will be on so the voltage will be around 13.5v. Im going to try one of them and see how they work out. Gonna report back when i we tried it out. The reason i wont order the Taskled H6CC is i guess the shipping cost would skyrocket and a importing fee coming afterwards. Gonna add a capacitor after and before the driver to try to stabilise the ripple from the vehicle and after the driver just to ensure that the ripple is minimal, because you never know about cjinese stuff :twothumbs


----------

