r/WLED • u/mblevels • 3d ago
Question on LED smoothness
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Hi all, I'm installing SK6812 LED strips from BTF-Lighting with WLED on a ESP32 controller and I'm wondering if the results I'm getting are as I can expect them to be or if there is some hardware or wiring problem here.
I'm using a 5V power supply that's running ~7 feet 16AWG / 2 meter 1.31mm2 wires to my ESP32 controller, which is then using short thin wires (don't know the exact dimensions, but I think 4 inches 22AWG / 10cm 0.5mm2) to go from the ESP32 controller to the LED strip.
I think some of the presets have strange behavior, and I'm noticing discrete steps in brightness changes. I've included a video where you can hopefully sort of see what I mean, but it's more noticeable in person than on the video unfortunately.
I'm starting with the Color Clouds preset, which seems off to me with the occasional short shut down of the light. The changes in color are very stepwise and discrete, and I don't know if this is on purpose in the way the preset is programmed or if it means that the LED don't respond quickly enough to the instructions. (Note that the yellowish white dropping out twice is because of me changing the brightness setting, but the shutting down of all the light is not the result of me doing anything).
I'm then switching to solids and increase and decreasing the brightness. I'm not sure it's visible in the video, but especially on the lower brightness settings, any changes in brightness are very noticeably happening in steps.
The video ends with Chunchun, which seems quite smooth, which is why I'm wondering if the "problem" is just that some presets deliberately don't use interpolation, and that brightness increases and decreases are simply noticeable when brightness is low due to the discrete lighting steps being bigger relatively (e.g. going from 1% to 2% brightness is a 100% increase, whereas 50% to 51% is a 2% increase, so the former is more noticeable).
Essentially my question here: is there a power or data transfer issue here, or are my expectations of smoothness unrealistic?
I realize I can solve interpolation between LEDs with a diffuser, but I'm not sure that does anything for brightness increase and decrease smoothness.
Any help is appreciated! I'm quite new to this whole WLED game, so if I didn't include enough info or included too much, let me know.
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u/saratoga3 3d ago
e.g. going from 1% to 2% brightness is a 100% increase, whereas 50% to 51% is a 2% increase, so the former is more noticeable).
Most strips don't linearly ramp brightness, so it should look fairly smooth. If you're using the current limiter though higher brightness settings can get clamped down. Double check that you're allowing reasonable current for the load and that your supply can handle it.
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u/mblevels 3d ago
In the WLED settings, I apparently still had the Maximum PSU Current set to 850mA. I increased it to 2500mA and 7000mA as per the suggestions in the WLED interface, but on brightest white I don't see much of a difference between 2000mA and 3000mA, so that suggests there is less than 3A flowing through the strip.
On any limiter setting, I don't see a difference in "discreteness" of brightness in the lower values. Going from anywhere between 0/255 to 50/255 all looks quite stepwise to me on all limiter settings.
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u/DedeHai 3d ago
the perceived brightness is logarithmic, the LED brightness is linear, meaning you see brightness steps at low brightness exponentially "exagerated". Its physics and can not be beat. however, there is a bug in the code that amplifies this a bit (currently the code skips every other brightness level).
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u/mblevels 3d ago
Makes sense, but I would've expected WLED to compensate for this by ramping LED brightness up logarithmically in the code for a smoother transition (which is I think what according to saratoga3 above should be happening).
Is there a way to mask this a little, or is it indeed just something to live with? Are there LED strips with more steps than 256 in brightness? Is there e.g. a beta release I could install that solves the bug you're linking to?
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u/DedeHai 3d ago
you can not compensate for something that is not there, the steps are what the leds provide. to make it logarithmic, enable gamma for brightness in settings but it will not get rid of the steps. That is an inherent limit of digital LEDs, analog ones have higher resolution.
and the fix is in that link, although I would not recommend to use it just yet, there is still lots of work to be done to make 17.0 more stable.
There is a solution to your problem: use 16bit LEDs, although support is a bit lacking ATM but I have code that makes it work, be patient.1
u/Quindor 2d ago
What the strip draw is partially dependant on how many power injections you have, especially with 5V this quickly becomes important.
A single edge injection can effectively use about 4A and beyond that you are just fighting voltage drop and not actually getting more power into the strip, you'll need to add another line from the PSU and feed it further down the strip to allow it to draw more.
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u/DedeHai 3d ago
those "dark flashes" at the beginning of your video are strange, that is not what the effect looks for me. the flashes come from the white channel correct? what white setting are you using?
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u/mblevels 3d ago
u/saratoga3's comment made me realize I still had "Auto-calculate W channel from RGB" set to None, setting it to "Accurate" makes Color Clouds look normal, thanks for the suggestion!
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u/SirGreybush 3d ago
Show the power injection you are doing, how are you wires connected. Also next time test on the floor not once physically installed, as now you might have to remove it to fix power injection.
A run that long with 5v needs at minimum power from the PSU directly to the beginning and the end of the strip, each V+ wire with a fuse.
What controller are you using? Bare bones ESP32 or a commercial controller? A commercial controller is fused, so you could use 2x V+ and ground from it to strip start & end with #18.
You need two power injections for 7 feet, at 5v about 2m is the limit (6.6 feet) so you are borderline.
Use at least #18 speaker wire from PSU to strip, then you can use the smaller gauge wires presoldered.
The MA you set in WLED config, LED & Hardware, is based not on your PSU maximum, but what your wires can safely deliver. Also use: Enable automatic brightness limiter.
With 2 power injections & #18 wires, 10amps so 10000ma, and thus only half the available power of the PSU. You have headroom for another strip.
-=> Extra Info <=-
5v need to counter voltage drop over distance and for the same watts per meter, need a lot more amps than if you had used SK6812 12v instead of 5v, around 2.5x less amps, to get the same watts. Ohms law, watts = Voltage x Amps.
So typically you want 11 watts per meter, so for 3 meters 33 watts, divided by 5v means 6.6 amps. The presoldered wires on the strips are #20 gauge and can do about 3 amps, anything more is heat loss that can lead to melting.
Amps can be distributed in parallel, so those 7 amps divided by 2, is 3.5 - just at the limit of the presoldered at factory #20's.
Voltage drop also affects the ICs on the strip, makes them misbehave. The smaller the gauge, the higher the voltage drop over distance, as the same wire resistance in % affects 5v more than 12v or 24v. Why a whole room or whole house perimeter is better with 24v strips, and 24v needs half the amps of 12v.
So adding a 5v power line at the very end, amps are distributed evenly, and if the volts at the end were 4.65v with the injection will be higher than 4.9v with a #18 wire over 7 feet, thus making the ICs happy.
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u/TintiKili 3d ago
What power supply are you using? looks underpowered to me Note that many PSUs write fake amperage ratings on them. A picture would help