Question:
There might be a fault with the strip because when I light it up using only red, blue, or green, the colors appear normal, but as soon as I try to blend any color, the beginning of the strip shows the desired shade—yet the color shifts toward the end.
My LED strip is powered every 5 meters along the 20-meter length. Yet at the end of the 20 meters, the voltage is a few volts lower than at the start.
I have already built such a 20-meter DRGB strip system, where there is no color difference; it works perfectly. What is the problem? Is the strip faulty?
An exaggerated experimental example for clearer understanding: 4 coils of 5-meter strips with 60 DRGB LEDs each, powered from only one end.
Answer:
Basic Information:
It is well known that there is a voltage drop along the LED strip; meaning the thinner the LED strip and the higher the power designed for its LEDs, the dimmer the light becomes the farther away we are from the connection point. Therefore, the denser the power supply, the more even and stronger the light we receive. This is all that is experienced with single-color LED strips, whether white, red, green, or blue.
Few realize that with RGB LED strips, not only the brightness but also the color shade changes at more distant connection points. This happens because each of the three primary color LEDs has a different so-called forward voltage. If we reduce the power supply to a LED strip designed to operate at 12 Volts, the blue LED will dim first, followed by the green LED, and finally the red LED will turn off when the voltage drops below its forward voltage.
“At the end of the 20 meter, the voltage is still a few volts lower than at the beginning.” Yes, the higher the power we want to transmit through a wire, the more noticeable its resistance becomes. Even if we use a wire with a 1.52 or 2.5mm2 cross-section, trying to deliver 100–200 Watts over 20 meters will inevitably cause a voltage drop. – It is possible to calculate how many Volts, but that is a separate post.
Let’s explore this in detail.
The total nominal consumption of the four rolls of DRGB LED strip shown in the above picture is 4×72 Watts; naturally, this would not be reached even if all rolls were powered from both ends. Manufacturers do not disclose what density of power connections would achieve the 14.4 Watts per meter consumption of the strip, as is the case here. However, we know that the higher the quality of an LED strip, the closer a 5-meter roll powered from both ends approaches its nominal consumption. Because of the DRGB strips shown in this picture, judging the quality of this product is further complicated by its DRGB nature. Setting it to fixed white light might not achieve the maximum power consumption we logically expect, as this also depends on how the DRGB controller was programmed. It may happen that the highest power consumption was intended by the programmer for some kind of light chasing effect.
But let’s return to the image below.
Set to minimum brightness, illuminated with fixed white light
Here, I set the controller of the strip to a fixed white light and reduced the brightness to the minimum. (Surely no one is surprised that RGB white appears as icy white.)
The total power consumption of the lighting shown in the picture is 10 Watts. That is, the strip emits an icy white light all along, with a visible decrease in luminous flux toward the far end, yet the color remains uniform throughout. From this, we conclude that the voltage drop is not significant enough to cause a color change. In other words, the cross-section of the LED strip is still sufficient for this level of power.
At the connection point, the 12 Volt power supply, under a total consumption of 10 Watts, dropped to 10.4 Volts at the end of the 20 meter strip.
Set to maximum brightness, glowing with fixed white light
I set the fixed white light to maximum brightness, resulting in a 32 Watt consumption. The nominal consumption provided by the importer for this strip is 14.4 Watts per meter, which is likely only achieved with ideally dense power feeding, making the maximum consumption 288 Watts.
About four meters of the strip is genuinely cool white. It’s not visible in the photo, but the center of the first roll is beginning to yellow. This means the voltage has already dropped there enough that the blue LED shows it first, as it has the highest forward voltage. In other words, the strip’s cross-section cannot supply the power needed for operation. The second roll is clearly yellow, so the blue LED can no longer shine with significant brightness. The third The coil is already red, meaning the green LED no longer works—only the red one does, because red has the lowest forward voltage. The 4. The red on the coil is also dim, as it is very close to the forward voltage; furthermore, the middle of the coil barely lights up, presumably the 5. The coil would barely flicker anymore. The 20. At the end of the meter, the voltage dropped to 6.7 Volts from 12 Volts.
At the connection point, a 12 Volt power supply with a total consumption of 32 Watts resulted in a voltage drop to 6.7 Volts at the 20 meter mark.
Let’s see if mixing just two colors creates a more pleasing effect!
Set to fixed orange light, with a dedicated orange button on the remote control
Set to fixed turquoise light, with a dedicated turquoise button on the remote control
Set to fixed purple light, with a dedicated purple button on the remote control
This is a simplified example to illustrate how, due to the different forward voltages of the LED colors, an insufficiently dense power connection can alter the original colors in color mixing situations.
It becomes even more striking with a high-performance (18 Watts per meter), but only 5 Volt DRGB strip, where this stunning effect can be seen over just 2 meters instead of 20, and indeed, with digital strips this faulty power connection looks even more spectacular.
The question naturally arises: what about analog strips?
RGB-NW LED strip directly operated on all 4 color channels
The picture below shows 4 rolls, which equals 20 meters of RGB-NW LED strip. This means it contains 30 RGB chips and 30 cool white chips per meter. Its nominal power consumption is 8 watts per meter, so the 20 meters nominally would consume 160 watts. Operated without a controller, so there is no power loss due to controller mixing. Therefore, the 20 meters are connected from one end, with all four color channels functioning. Consequently, it should shine almost entirely with cool white light, since the RGB white is cool white, while every second white chip is cool white. So, instead of the theoretical 160 Watts, the construction shown in the picture delivered only 25.5 Watts of total power.
The first coil displays a fairly accurate cool white, while the center of the second coil is already turning green, around the 9-meter mark. At a meter, it shifts more toward green, then gradually produces a fading yellow-green light.
Why didn’t it reach the red? Presumably, the cross-section of the strip and the power ratio of the LEDs on it are more favorable. Nominally, this strip only uses 8 Watts per meter, unlike the above DRGB, which is rated at 14.4 Watts. Furthermore, of the 8 Watts, 4.2 Watts come from the white chip, which, although it will never show color, will simply dim over time. The key point is that at the connection, a measurable 12 Volts is present for the 20. At the end of the meter, it dropped to 7.3–8.8 Volts, which is higher than the DRGB (measured here) at 6.7 Volts. That is, around 8 Volts the green is still above the threshold voltage, so the end of the strip is yellow-green rather than red.
Also, with analog color mixing, the red is weaker than the green, and we should actually see yellow, but because of this, the yellow appears only as yellow-green – but that is another story. If we observe, on the last two coils the white chip is no longer lit, not just the blue.
At the connection point, the power supply is 12 Volts with a total consumption of 25.5 Watts along the 20- meter length, but the voltage drops to 7.3–8.8 Volts by the end. Voltage varies across the 4 color channels, with white being the highest and red the lowest.
To briefly and clearly answer the specific question from the interested party:
Based on what was described, I believe that although the power connections were made every 5 meters, a single connection error somewhere can instantly turn those 5-meter intervals into 10 meters. It can also happen that there is a continuity fault in the trunk cable (a Wago clamp was attached incorrectly, touching the insulation), so in one section, the power only runs along the tape and then, at the next power connection on the tape, it goes back to the trunk cable.
If there are no such faults, then I must assume that the cross-section of the trunk cable is insufficient—at least 2×0.75 is needed—although I usually recommend the cross-section with the far end of the trunk also connected to power; in other words, when creating a circuit, this makes sense and the cross-section effectively becomes 2×1.5. If we install a backbone cable connected at one end in a straight line, the equivalent is 2×1.5.
TL;DR – Brief summary
(Open the arrow if you can´t see it!)
This article explains in detail why the end of the LED strip lights up in a different color than the beginning and how to solve this problem with the correct wiring. The correct methods and tips for wiring LED strips help to avoid color differences and ensure that LED strips shine evenly. The LEDrex Web Store offers the necessary components and detailed instructions to help you install and operate LED strips correctly. Discover the world of LED strips and solve the color difference problem easily and effectively.
In this article, you can read about the following topics:
- Question:
- Answer:
- Basic Information:
- Set to minimum brightness, illuminated with fixed white light
- Set to maximum brightness, glowing with fixed white light
- Set to fixed orange light, with a dedicated orange button on the remote control
- Set to fixed turquoise light, with a dedicated turquoise button on the remote control
- Set to fixed purple light, with a dedicated purple button on the remote control
- RGB-NW LED strip directly operated on all 4 color channels
- To briefly and clearly answer the specific question from the interested party:
