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I'm new to the forum found this using google.

i have 2 (Two) 5050 RGB 12V LED Strips that are 5M/16ft. It's not as bright as i'd hoped it would be. I double powered one of them with the cheap power supplies they came with and it's a little brighter almost to what I want. Searched for the brightest RGB LED strip and i found it only comes 5050. It's not as bright as i hoped. Since i double powered it on both ends and it got brighter, would it be safe to power it with a 16V 4.5A laptop power supply since there's some power lost due to strip resistance? Or is 14V the max recommended?

Or would the safest way be dual powering them with 12V or dual 14.4V? Would single 14.4 3A perform better than dual 12V 1-2A (that i currently have)?

I'm looking for a LED's for a store window display. I have merchandise in the window. Will 5050 do or do i need to step it up to 5630, 7020, 8020? I was hoping 5050 would do since it's RGB and we can have a Christmas display going. There are plenty of windows so i could do 5050 for the RGB and the brightest Warm White (not cool white which is most common for super bright)...

would it be safe to power the 5050 RGB 5M LED Strip with a 16V 4.5A laptop power supply since there's some power lost due to strip resistance? Or is 14V the max recommended? The lights stay on from 10am to 6pm. Monday-Saturday.

Or would the safest way be dual powering them with 12V or dual 14.4V? Would single 14.4 3A perform better than dual 12V 1-2A (that i currently have)?

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  • \$\begingroup\$ Pretty sure you asked the same question 3+ times in that mess of text. Didn't even provide part numbers. I assume the LED strips have built in driving resistors? Was there a voltage change when you added the second adapter in parallel? Unless the adapter doesn't provide sufficient current (in which case get a heftier supply), only reason for the LEDs to brighten would be tying the supplies together caused the input voltage to rise. \$\endgroup\$ – I. Wolfe Feb 19 '15 at 19:22
  • \$\begingroup\$ Thanks for your response. These are the strips ebay.com/itm/391044936635 . 5050 RGB 5M/16ft 12v numbers on the resistors are 331 and 151. the strip is white. \$\endgroup\$ – Peter Feb 19 '15 at 20:09
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Increasing the voltage by that much will significantly increase the LED current - much more than you might think.

Most of those strips have 3- LEDs in series per section. The forward voltage on a Green or Blue LED is about 3.2V. The Red LEDs are about 1.7V each.

The intended voltage for those strips is about 12V. Let's use that as a starting point.

The increase in current for the Green and Blue LEDs is going to be about:

@ 12V: 12V - (3 * 3.2V) = 2.4V across the current limit resistors

@ 14V: 14V - (3 * 3.2V) = 4.4V across the current limit resistors

@ 16V: 16V - (3 * 3.2V) = 6.4V across the current limit resistors

So: increasing the supply voltage from 12V to 14V is going to increase the LED current by (4.4 / 2.4 * 100%) = 183%

Increasing the supply voltage from 12V to 16V is going to increase the LED current by (6.4 / 2.4 * 100%) = 267%

The situation is a little better with the Red LEDs. Doing the same math as above results in the following voltages across the current limit resistors for the Red LEDs:

12V: 6.9V across the current limit resistor

14V: 8.9V across the resistor

16V: 10.9V across the resistor.

That results in a 129% increase in current if running at 14V; a 158% increase in current if running at 16V.

I strongly suspect that the current limit resistors are going to be really unhappy. You will most likely also notice that the Red LED didn't get as bright as the Green & Blue LEDs at the higher voltages.

Bottom line: run the strips at the manufacturer's maximum voltage and feed power from both ends if possible.

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  • \$\begingroup\$ Current wise, it will push over 40 mA per series connection, for diodes that are typically rated for 20mA. If they don't burn out immediately, they will soon enough. \$\endgroup\$ – Passerby Feb 19 '15 at 20:59

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