still the voltage on an end of a strip is always lower as where the cennection is
using 19V PWM is just stupid, as the current is well over the rated with a tint shift
I have done 120LED/m 5070 stips with connections on both ends and 2m lenght, there is a decent voltage drop of about 1.5V in the middle
Lexel, good point. I am still learning about this so let me see if I understand it correctly: using 19V on a 24V setup will increase the current thought the Leds (as the resistance will not change) causing the tint shift, right? What would happen with the opposite? Powering a 24V with 30V for example. The current would decrease? and it would also cause color tint shift?
Let me ask you something about the tint shift in another situation if I wanted a really low output from these lights (I know I can always use PWM at the stated voltage, but for the sake of theory): what happened if I power a 12V led strip with a 5V powerbank? The current would increase until the USB reach its max current. And that is probably too low. These leds would run with less current, would they also have tint shift (or would they turn on at all)?
The second situation would be the follolwing: powering a 12V led strip with a limited current 12V power supply. The leds would be less bright and less color accurate?
Powering 12V strip the safe way is 100% current no PWN,
then measure on the strips input voltage where the leads are soldered and adjust the PSU voltage till it reaches 12V, maybe a few 0.1V more
Depending on current, gauge and length of the cables this may be 12.5-13.5V
if he is using 19V thats just stupid pulsing the LEDs current likely over their specs
19V on a 12V strip is killing them - no matter if he is using PWM or not.
19V on a 24V Strip will barely light the LEDs up and they will pretty much live forever
12V Stripe on 5V Powerbank doesn’t work - 3 LEDs in series need ~7-8V to light up a tiny bit.
Wow their WW 3000k actually has a negative DUV value and 93.53 R9!!! I’ve been searching for good led strips for my home decor and all the Amazon ones I bought have very yellowish/greenish tint. I would love to buy a 3000k one but they only sell NW 4000k-4500k and CW 5500k-6000k.
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.