Direct backlight LED strips in 48" Samsung TV...

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Externet
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Direct backlight LED strips in 48" Samsung TV...

Post by Externet » Wed Aug 16, 2017 10:59 am

Hi.
There is eight strips of four LEDs for a total of 32 LEDs; they are in series; they look like :

----> http://www.ebay.ie/itm/SAMSUNG-UN48J520 ... SwG0BZbsw7

What is the voltage supply ? Is it 96V ? Following the board circuitry, there is 400V electrolytics on the power rail before the driving mosfet.
From this site, seems like 3V per LED. Max? or rated? current seems 350mA. Unsure of which LED chips uses or if there is limiting resistors on board the strips.

----> https://www.aliexpress.com/item/NEW-Bac ... 40877.html

This deceased by cracked screen TV is my next flush ceiling lamp, want to power the backlit diffuser panel properly.
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jwax
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Re: Direct backlight LED strips in 48" Samsung TV...

Post by jwax » Thu Aug 17, 2017 8:07 am

Maybe the ebay seller could answer that.
2-3 volts each is typical of LEDs, but series/parallel wiring will dictate what power source is needed.
Could always power it up starting low, slowly increase voltage until they get a little too warm?

Flat panel ceiling lamp, eh? Nice project! I'd like one of those that simulates solar spectrum for those cloudy winter days!

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Ronaldlees
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Re: Direct backlight LED strips in 48" Samsung TV...

Post by Ronaldlees » Thu Aug 17, 2017 10:34 am

Hello Externet:

Great project! That TV is thirty pounds (weight) - so I suspect you'll be trimming out the un-needed stuff. Would be a wrecking ball when it fell!

From a quick survey on search sites, it looks like available info about that model is almost nil. But - like jwax mentioned, you could remove a strip, and alligator-clip a couple sewing needles to wires which you then connected to a constant current supply (one that maxes at about 3.5V or less). You could poke the traces around one of the LEDs until it lights up (suggestion I found elsewhere on the net).

Set the constant current to a pretty low value, as jwax wrote. Slowly increase, and when the LED lights, ramp up the current until it has a reasonable output of light - (from what I've read about white backlight LEDs, that's somewhere in the area of 3 VDC (plus a little maybe)). It's the current that counts, it's what you want to control closely since the diode will take off fast at its knee voltage. You'd have to experiment, but at the sweet spot current level, let it run a while and see if it gets too hot. If too hot, back it off a little. Note: I'm not an expert - most of this I looked up today. So, take with grain of salt.

On Amazon, type CVCC and you'll see a bunch of the constant current modules they sell for battery charging - good for about 500 mA. I've found they're perfect for things like this (testing low current where CC source needed). There's two pots on them, (one for current, one for voltage) - so can keep all parameters under control. I think they're about 9 bux with free shipping.

Sounds like a great project. I have an old junker here, myself. You may have given me an idea! Thanks.

- Ron

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Externet
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Re: Direct backlight LED strips in 48" Samsung TV...

Post by Externet » Thu Aug 17, 2017 1:15 pm

Well, it won't have a LCD panel to shatter anymore if it falls...
No need to remove the strip, their wiring is accessible at their connector. Did a very conservatively test with limited 20V and got the glow.
A ceiling lamp for my workbench should be better than for looking at x-rays.
I will follow the nose on current. If the typical rate seen is 350mA; I chose/ordered a 300mA driver, should arrive in a few days :

----> http://www.ebay.com/itm/30W-High-Power- ... SwjvJZOhfS

The power supply that belongs/drives that TV LEDs is PWM controlled for brightness and already disemboweled. Too late to attempt measure voltage/current. Will see the color of the smoke -or not- soon with the driver linked.
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Ronaldlees
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Re: Direct backlight LED strips in 48" Samsung TV...

Post by Ronaldlees » Thu Aug 17, 2017 5:45 pm

At $10 and free shipping, it seems it'd be hard to beat the price of that driver you listed with the link. I looked at a pic of the BN44-00852A supply/LED driver board, but it was too fuzzy to tell much. Not even sure if that's the correct supply anyway. I'm not really a TV guy.

Anyway, hope it works to light your workbench.

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MicroRem
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Re: Direct backlight LED strips in 48" Samsung TV...

Post by MicroRem » Thu Aug 17, 2017 9:20 pm

Neat project... nothing to contribute but am following with interest.

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Externet
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Re: Direct backlight LED strips in 48" Samsung TV...

Post by Externet » Mon Aug 21, 2017 5:29 pm

Done. Installed in the basement. With the help of a 'shoehorn', fitted in the 24" ceiling panels railings width as the TV is 24 1/2"
Result is surprisingly better than expected, am more than happy :grin:

By the way, the removed cracked LCD panel served very well earlier today to see the eclipse holding it overhead ! :mrgreen:
P1010689.JPG
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Re: Direct backlight LED strips in 48" Samsung TV...

Post by vision » Mon Aug 21, 2017 8:37 pm

That would be a good project for Nuts & Volts to use in there magazine article.

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