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5v vs. 12v question


gmac
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What are the differences between 5v & 12v pixels besides the power they consume?  I plan to purchase pixels and was wondering if there is a difference in brightness or longevity,  or can longer runs of pixels be made without more  power injection between the 2 voltages.

I was hoping  users with more experience with pixels could answer this for me, and also give some input to issues between the 2 that I haven't even thought of.

 

Ii poked around the forum but couldn't seem to find the answer

 

Thank You in advance

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If you are talking WS2811 pixels on flex strips, you are looking at 3 LED clusters per "pixel" for 12v as opposed to 1 LED cluster for 5v.  The voltage drop become less significant but the control is not as resolute.  

 

As for the power, they both take about the same.  Power is voltage x current.  Drop the voltage and the current goes up, and visa versa....

 

If you are talking individual pixels you should remember that the chip is only a 5v chip and the voltage has to be dealt with some how.. that means regulation of some type.  That means heat, and/or complexity. 

 

There are trade offs to either direction.  You should figure out what you want to do then how to do it.  The more specific you are, the better help you can get for your solution..

Edited by plasmadrive
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Just so you know not all 12v pixels have voltage regulators. I had Ws2811 pixels from Ray that were 12v no voltage regulator. If you lowered voltage to even 10.5v the pixels started changing colors showing there were not regulators bringing voltage down to 5v. The ones with regulators are the ones to watch out for.

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Just so you know not all 12v pixels have voltage regulators. I had Ws2811 pixels from Ray that were 12v no voltage regulator. If you lowered voltage to even 10.5v the pixels started changing colors showing there were not regulators bringing voltage down to 5v. The ones with regulators are the ones to watch out for.

If they were not multiple LEDs in series then they had to have the proper dropping resistors for the 12v input.. Not sure what they would have done for the chip voltage because 2811s are only 5v chips.

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You are correct that they use a dropping resistor for the 12vdc individual lights, but what you find is that they usually drive the LED at 1/2 the current and will output around at 9.5mA, the reason for this is to reduce the wasted heat energy that needs to be dissipated through the drop down resistor and reduces heat issues. The effect that this has on light output is hardly noticeable as we don't see LED light dimming as linear so when the current is reduced for the LEDs then we don't perceive a great deal of difference. This would be more noticeable using a light meter and maybe the amount of light wash created may also be less.

 

Now there are some strip and lights starting to appear that use voltage regulators to power up 500mm sections, so these lights are designed to run on 12vdc or 5vdc and retain the same efficiency.as 5vdc

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Just got done reverse engineering the 12V WS2811S chip with 3 of the RGB SMD5050 LED strips. I have had several failures much like many others. What  I found is that the circuit for the RED LEDs has a 240 ohm resistor in series. Also there is a 3.3K resistor from the V+ to the WS2811 chip. From what I found about the WS2811 spec sheet. This chip is supposed to have a V+ of 6 to 7 VDC. Also the chip is a PWM constant current chip. But I am thinking that there is a small window of control. This is the reason that the RED LED fail. Per suggestions of others I have lowered the V+ voltage from 12 to about 10.7 volts. But this also lowers the voltage at the WS2811 to about 5.7 volts. I tried to find some SMD 5050 RGB LEDs, but none of them where configured in the proper physical configuration. So, looks like I will buy another strip and use it as a new strip. Use one of the bad strips to repair two of the other strips. Hope that some of the 5V nodes I buy from Ray fair better.

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I plan on using 12 volt stuff just because I can use the leftovers in my cars and trucks. Lol

I wouldn't count on that. 12V pixels may not be very tolerant of the 13 to 14.5 volts often seen in a car when running.

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Just got done reverse engineering the 12V WS2811S chip with 3 of the RGB SMD5050 LED strips. I have had several failures much like many others. What  I found is that the circuit for the RED LEDs has a 240 ohm resistor in series. Also there is a 3.3K resistor from the V+ to the WS2811 chip. From what I found about the WS2811 spec sheet. This chip is supposed to have a V+ of 6 to 7 VDC. Also the chip is a PWM constant current chip. But I am thinking that there is a small window of control. This is the reason that the RED LED fail. Per suggestions of others I have lowered the V+ voltage from 12 to about 10.7 volts. But this also lowers the voltage at the WS2811 to about 5.7 volts. I tried to find some SMD 5050 RGB LEDs, but none of them where configured in the proper physical configuration. So, looks like I will buy another strip and use it as a new strip. Use one of the bad strips to repair two of the other strips. Hope that some of the 5V nodes I buy from Ray fair better.

 

 

My calculation put the resistor value for the red if using a forward voltage of 2.3 volts per LED and 18.5mA output from the 2811 as being a value of approx 330ohm The reistor value for the green and blue if the forward voltage is 3.2 volts would be approx 150 ohms. So looking at this it appears the Red resistor value is actually too low and this may be the reason for the reds mainly failing.

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My calculation put the resistor value for the red if using a forward voltage of 2.3 volts per LED and 18.5mA output from the 2811 as being a value of approx 330ohm The reistor value for the green and blue if the forward voltage is 3.2 volts would be approx 150 ohms. So looking at this it appears the Red resistor value is actually too low and this may be the reason for the reds mainly failing.

I think this is already documented as an issue if I remember correctly.. Was supposed to have changed on later versions.

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Well we will see when I go to order a new 5 Meter strip of the same. I might take a look at it again shortly. Didnt take notes but think the Green and Blue are more like the 3.6V. But agree, things might have worked it they had used a 330 ohm resistor inline with the red LEDs.  Seems that the vendors are in comp with each other and they will push the limits of the LEDs to get max light out of them. Hell with the life being shorter.

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Well we will see when I go to order a new 5 Meter strip of the same. I might take a look at it again shortly. Didnt take notes but think the Green and Blue are more like the 3.6V. But agree, things might have worked it they had used a 330 ohm resistor inline with the red LEDs.  Seems that the vendors are in comp with each other and they will push the limits of the LEDs to get max light out of them. Hell with the life being shorter.

 

This would also have to do with the bins the LEDs come from. there is a reason why rays lights are cheap and thats because he uses lower quality binned LEDs and maybe the red output may not be as good as what it should be so instead they crank up the Red LED that little more to make it look better

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edvas69

That would make some sense. I happened across a sight called www.superbrightled.com . Their 5 Meter strips are more like 70 bucks, and I can drop by on the way home from work. But holy bat crap! That is no longer a hobbyist price. And as I mentioned, them SMD 5050 are not what might be called standard physical configuration.

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