I want to put strips around the parameter of my room that is about 46 feet. I want 12V LED to avoid or reduce power injection. What LEDs do you recommend? So far I just have a DIG uno.
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Hi so yeah pretty much i've got led strip that was meant for house use and now i wanna put it in my van to run off 12v. I do have an inverter but would be nice to just connect it to my battery. Anyone knows if it can be done?
We want to brighten up our back patio under the gazebo at night, and I'm looking into 12v LED strip lights, which we could run along the inside of the frame around the roof line. But there are just so many options, I'm getting lost and looking for recommendations.
I'd like something that could be wired into our existing 12v landscape lines, even if that means cutting off a provided transformer and splicing it manually. We're also looking for something that could be color-changing via remote (or app). The gazebo itself is 14x20 so to run arounds the full perimeter we're looking at around 70 ft.
The perfect setup would start with the existing landscape lighting 12v line at the bottom of one corner post, connected to the light-strip set, and I'm assuming there would be some "controller" inline for a remote control to "talk" to and control light settings, and then from there start at one corner of the gazebo roof and just wrap around.
Any suggestions for a brand that's well-made, works well, and doesn't fritz out after a single season?
Thanks!
12V might be the "quasi" standard because of the 12V car batteries/electrics that were there years before the LED strips.
Of course no one is driving a single 3V led with 12V and a resistor directly. That would be too much energy loss.
Since there exist DC/DC converters which can transform voltage with a good efficiency from one voltage to another, it does not matter so much what voltage is used as primary source.
Another thing is that you can put the LEDs in series until you get the required voltage (4x 3V = 12V).
There are lots of issues with using 3V directly. For starters, the forward voltage of an LED is related to the wavelength of light it produces, ranging from about 2V or less for red to about 3.6V or more for blue. So no single voltage is going to work for all three colours and devices that run from a single supply would have to be given enough voltage for the blue LED and regulate it down for the others anyway.
Second, LED current varies drastically with supply voltage and temperature, so trying to use exactly the right voltage supply and trying to keep it correct through wiring, connectors, switches and controllers is a non-starter, and on top of that, variations between individual devices would produce uneven illumination. So instead, they're driven with constant current and that requires a higher supply voltage that can be regulated down as needed to cope with the variations.
So given that a higher voltage is needed, it's just a case of choosing an appropriate one. 6V or 9V could work, but 12V is a widely used standard, especially in the automotive world, it was already in common use for low voltage lighting and it allows plenty of headroom for voltage drops in distribution and regulation. And if the regulation is done using buck converters the higher voltage allows for lower supply current and reduces the power loss through distribution still further.
Common led strips take about ~18mA at 12V per segment (typically 3 LED). They are used in Automotive 12V rails, which is 12V nominal, but can go to 14V regularly, with larger spikes.
If you look at a segment, you will notice it has three LEDs and one resistor. Based on the color of the led and ohms law, you can figure out it's current at any given voltage.
$$I = \frac{V_s - V_f}{R}$$
Assuming a white or blue led with ~3.2V forward voltage drop, which is typically paired with a 120Ω resistor:
$$\approx 18mA = \frac{12V - (\approx 3.2V \times 3)}{120Ω}$$
At 14V, you get:
$$\approx 36mA = \frac{14V - (\approx 3.2V \times 3)}{120Ω}$$
This isn't exact. The higher the source voltage and current goes, and the LEDs forward voltage drop does change a bit. At ~36mA the LEDs are being over driven, shortening their life some, so you won't get 1000~5000 hours that they should give at 20mA. But its normal to overdrive them. And they will be brighter to boot, so you might even need less LED segments.
But now lets change the source voltage to 16V:
$$\approx 53mA = \frac{16V - (\approx 3.2V \times 3)}{120Ω}$$
53mA continuous is almost 300% of the typical recommended current of 20mA. But at 53mA, the forward voltage drop goes up as well, making the math tricky. The life of the leds will be much shorter, and they will warm up considerably.
Solution: As others have mentioned, you can use Silicon Diodes to drop the source voltage. You can use from 3 to 9 (Dropping 2.1V to 6.3V), depending on how bright you want the leds, how much current the strip should pull, your batteries voltage range (A 4S Lipo is 14V Nominal, 16.5V at max safe charge, 11.5V at lowest safe discharged voltage).
Best thing to do, is take one or two segments of the led strip and TEST THEM. Connect one directly at the charged 16V and see how long it lasts or how hot they run. Look at the resistor and do the math. Then start adding Silicon Diodes and see the difference.
The easiest way, then, is to find out how much current the LED strip draws with 12 volts across it, and then to connect 7 silicon (not Schottky) diodes rated for that current or greater (greater is better) in series with the LED strip and the LIPO.
Depending on how much current they have to handle, they could get pretty warm, so you might want to place them somewhere where air can blow over them to cool them.
If you use 1N4001 or 1N4002 diodes, figure about a 0.8 volt drop each with 750mA through them, so you'll need about 5 or 6 in series between the LIPO and the LED strip, like this:
+--[DIODE>]--[DIODE>]--[DIODE>]--[DIODE>]--[DIODE>]--[DIODE>]--+
+| |+
[LIPO] [LED STRIP]
| |
+--------------------------------------------------------------+