Well, guys, he actually connected 2x12V LED strips in series, then to reduce heat output and boost efficiency, he put 19v instead of a 24V power supply. Then he uses PWM to reduce power even further.
He wouldn’t be that dumb to power a single LED strip with 19V+PWM. That is why he put 2 in series. Watch the whole video, and you will understand.
I understood that but, at first, I though Lexel had not. I was going to explain this to him, but then I tried to think.
He stated:
Undervoltaging means more current (since the resistance does not change), right? As he stated, more current = color shift.
So, I think he meant undervoltaging a 24V LED system to 19V means more current, so tint shift. Did I understand right?
Undervolting means less current - until the LEDs don’t light up at all.
The forward voltage of every LED gets less if you lower the current - and vice versa.
Visualisation:
The more current you want, the more voltage you need
The more voltage you want, the more current you need
So, if you give the LED which this graph is about exactly 3V, it will draw ~75mA. It is impossible to run this LED with 3V and 300mA.
24V LED-Stripe on a 19V Power Supply means lower current, therefore a tint shift.
PWM dimming doesn’t affect the tint as hard as dimming via current does, but it does.
Understood, thanks for the nice explanation and graph! I was stuck with Ohm law, U=Ri but apparently the resistance of the LEDs are not constant.
But aren’t these leds connected with a much higher resistor in the strips? I thought that this much higher (and fixed) resistance is the one who will determine the current through the strip?
Found another 90CRI strip. I asked for the 3000k version and they showed me a test report showing x=0.4275 and y=0.3814, which calculates into a DUV of –0.008, which is very nicely rosy! Perfect for the living room or bedroom use!
61lm/W
good God…
That’s why I don’t buy chinese LEDs anymore - efficiency-wise they stand still for the last 10 years.
The Samsung LM301B are over 200Lm/W and some other LEDs are very close to 100CRI/Ra - It’s just a matter of time until they get combined.
That said, the 80CRI of the LM301B is not bad, I have several 4000K modules, but 3000 and 5000K as well - I would use them for house lighting anytime.
Where do you buy the Samsung strips? Are there test results? Wjere do you find led strips with 100CRI?
Im interested not just in the CRI or R9, the tint is just as important if not more. I cant stand yellowish greenish tint. It needs to be under BBL for me and the ALI one I posted has a DUV of a whoping –0.008. That might be the reason why the efficiency is not good. It is like a Nichia 219B 9080. Beautiful tint but poor efficiency.
These are not LEDs but strips with current limiting resistors. Possibly driving the LEDs at more than optimal current. At 3000K CRI 9080.
61 lm/W is not really good, but it’s not particularly bad.
You cannot compare efficiency of LEDs with LED strips. The resistance (losses) through the strip is tremendous. It’s like comparing the horsepower at the crank vs at the wheels but many times worst. Many of these 16.4’ strips actually have visible dimming at the end of the strips due to resistance losses. To me the tint is even more important than CRI for interior lighting and most of the ones I bought were too yellow/green or did not have enough red/rosy tint in them for my tint snob eyes. During my house remodeling I bought about two dozen different types of LED strips from Amazon and local stores including cheap and premium brands and weren’t happy with any. I then found a random low cost $10 strip from a website I never heard of at the time (Aliexpress) and bought it. It was the brightest and best tinted (not sure about CRI) led strip I’ve seen yet so I ordered another 10 because I used it in all my rooms and kitchen.
Now if anyone know of any LED STRIPs with good tint (negative DUV) and 90+ CRI with better efficiency or higher brightness than the ones posted above, regardless of price, please post. I’ve looked hard for LED strips and even tried the expensive stuff but still haven’t found any ideal LED strips.
I took a look at the data sheet of the Samsungs and looks like they will be averaging above the BBL so it’s going to be on the green side unless you can select tint bins. I’m guess this is similar to the high cri Cree emitters that are famous for having the highest efficiencies but piss ugly tint.
I have those Modules in 3000K, 4000K and 5000K - none of them has any ugly tint - and I had a ton of 5m cheapo stripes with yellowish “warm” white or blueish “cold” white.
I plan to use the 3000k under kitchen cabinets and living room. The 4000k is great for garage. However, these lights emit too much blue wavelengths to be used in the bedroom. I’m going to buy 2700k for the bedroom.
Edit: I just installed the Sidawang 3000k under cabinet and at first I thought I accidentally installed the 4000k version because it looked so neutral white compared to my older 3000k led strips that were turned on at the same time. I then measured their CCT and surprisingly the Sidawang 3000k was actually about 50k warmer than my previous 3000k strips. My previous 3000k had a duv of 0.005x. The lower DUV on the Sidawang made it look 1000k cooler. Not sure if that is a good thing or not because I like some warmth in my emitters. I will try the 2700k and hopefully the very negative duv will make it look just right. Btw, I don’t really notice rosiness in the Sidawang 3000k in actual use. The older 3000k strip looks very yellow/lime in comparison though.