Page 3 of 3 FirstFirst 123
Results 21 to 24 of 24

Thread: Are there higher voltage pixels?

  1. #21
    Join Date
    Jun 2011
    Posts
    1,550
    Post Thanks / Like

    Default Re: Are there higher voltage pixels?

    Quote Originally Posted by madsci1016 View Post
    The only real debate here is money vs. build time. 12V are more expensive and require more power supplies for the same prop, but they are easier to build with less power injection. 5V will save you money but require more injection points. Both avenues can be 'cheated' a bit by reducing max brightness. Everything else is just us engineers making noise about good design practices.
    Ha ha.. we do that a lot I think.. I know I am so guilty of that....

  2. Likes beeiilll liked this post
  3. #22
    Join Date
    Nov 2009
    Location
    Brisbane - Australia
    Posts
    904
    Post Thanks / Like

    Default Re: Are there higher voltage pixels?

    I bought some 24V pixels a while back (6803 type so that shows how long ago!), but they were modules with 6 LEDs.
    20 character sig !!!

  4. #23
    Join Date
    Dec 2014
    Location
    Florida
    Posts
    857
    Post Thanks / Like

    Default Re: Are there higher voltage pixels?

    Quote Originally Posted by rhildinger View Post
    The salient points of the whole 5v vs. 12V discussion are thus:

    1. The WS2811 chip (and others like it) driving these pixels provides a constant-current supply to drive the LED’s, but it does not do any sort of buck conversion, which means the electrical characteristics are defined by current in = current out, NOT power in = power out. In other words, the same amount of current is required to drive the LEDs regardless of the voltage being supplied.

    2. To drive a string of 100 pixels full white (20ma per channel x 3 channels = 60ma) at 5V requires a power supply that can deliver 60ma x 5V x 100 = 30 watts.

    3. To drive a string of 100 pixels full white (20ma per channel x 3 channels = 60ma) at 12V requires a power supply that can deliver 60ma x 12V x 100 = 72 watts.

    4. In the 5V case, each pixel is consuming .3 watts, and in the 12V case each pixel is consuming .72 watts. They are producing the exact same amount of light, so the entire .42 watts of extra power that the 12V pixel consumes is wasted as extra heat generated at the pixel node.

    5. To compensate for the dramatic increase in power necessary to drive the pixels at 12V, some manufacturers will lower the per-channel drive current to 15ma or even 10ma. Setting the drive current to 10ma for our 12V string example (full white- 10ma per channel x 3 channels = 30ma) means that we only need a power supply to deliver 30ma x 12V x 100 = 36 watts. The idea here is is that cutting the drive current in half results in a very minimal decrease in perceived brightness, due to the logarithmic nature of our eye sensitivity.

    6. A 12V-driven pixel is not inherently brighter or dimmer than a 5V-driven pixel, it is only if the manufacturer chooses to lower the drive current of the 12V pixel that it might appear to be slightly dimmer. The only way to know beforehand is to see the manufacturer build specs.
    Yep, better laid out for everyone, thanks. I do want to clarify the power calcs though.

    7. LED forward voltage is typically 2V for Red and 3.2V for Green and Blue. So at 5V, we are actually using 0.168 Watts for the LED and wasting 0.132 Watts as heat. At 12V, we are still using 0.168 Watts for the LED but now wasting 0.552 Watts as heat. FOUR TIMES as much electricity wasted as heat than a 5V pixel. Scale up to 1000 pixels and you are losing 500 Watts solely to heat and had to buy two more 300W power supplies. THIS is why I'm so strongly against 12V unless it's really needed.

    I believe most manufacturers do reduce the current, and therefore brightness. I can't see how the 12mm node package can dissipate half a watt, outdoors in the Florida heat (for some of us) so I'm more inclined to believe HolidayCoro over Raywu. I do suspect it's more like a reduction to 10mA like you say, which brings the power down to 0.084 Watts for the LED and 0.276 wasted as heat.

    Which means the LED is half as bright (due to half the drive current) but wastes twice the power. Back to my original statement. Maybe it isn't half, maybe it's 25% like it's reflected in HC, but it's still 3 times the power loss for 75% the brightness.
    Last edited by madsci1016; 01-11-2017 at 09:10 PM.
    www.billporter.info
    2014 Christmas: 1 Channel; a new house and a crazy plan.
    2015 Halloween: 2500 Channels; 3 songs. Christmas: 4500 Channels; 6 songs. Custom Wifi Pixel/Renard Controllers
    2016 Halloween: 6500 Channels; 4 songs. Christmas: 11,000 Channels; 4 songs.

  5. #24
    Join Date
    Nov 2011
    Location
    Chicago - Southwest Suburbs
    Posts
    6,235
    Post Thanks / Like

    Default Re: Are there higher voltage pixels?

    What some (in flordia) call power loss, others (farther north) consider a benefit. I don't consider it wasted power. I consider it savings in the amount of energy I need to spend on keeping ice and snow off of the pixels. That's one of the biggest drawbacks for LED displays in cold climates, they just don't keep themselves clear of snow and ice like the old lights did. I actually have to put heat sources on some of my props to manage the snow load.

  6. Likes kychristmas liked this post
Page 3 of 3 FirstFirst 123

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •