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A Dirty Secret. Pixels Are Power Hogs.


Chuck

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I built some big pixel trees in 2014.  16 vertical elements per tree, each with 170 pixels.  Good gosh you could create some amazing, jaw dropping effects.

 

Pixels are low voltage devices so you need special power supplies to convert 120-240 volts alternating current down to 5-12 volts direct current.  That low voltage then powers the pixel elements.  I couldn't help but notice the fans in those power supplies came on a lot when the tree was really dancing... didn't think too much of it.

 

I decided to run some power tests during the slow season.  Bought a wattmeter gizmo that would tell me exactly how many watts a pixel tree was consuming at any given time. 

 

This is where things can get confusing.  An individual pixel draws very little power but when you have a bunch of them the total watts consumed go up fast.  To further complicate things, something that draws 12 watts at 12 volts draws only 1 watt at 120 volts so you have to be careful when you talk about watts.  To muddy the waters even more, those power supplies that convert high voltage to low voltage aren't all that efficient... meaning 15-30 percent of the power is consumed by the electronics and/or wasted to heat and not available to power the lights.

 

Here's where things get interested.

 

As a point of reference, I connected an old fashioned 100 watt incandescent light bulb to my wattmeter gizmo and it read 100 watts being consumed at 120 volts AC.

 

In the world of Light-O-Rama 16 channel controllers with zillions of lights (incandescent or LED) plugged into the channels, when the lights are all off, each controller is sitting idle and consuming about 5 watts of power at 120VAC according to my wattmeter gizmo. 

 

In the pixel word with those low voltage power supplies and the sophisticated pixel controller, when all the pixels are off on a big pixel tree, I was consuming about 75-80 watts of power at 120VAC.  When the tree started dancing it could be consuming 600-800 watts of power at any given time.  600-800 watts... that's a lot of juice.

 

When nothing is happening you're drawing a lot of power.  When the lights are dancing you're drawing a whole lot more power.  Interesting.

 

Now in the big scheme of things, electrical power is pretty cheap.  In my part of the world, that 100 watt bulb run for 10 hours would consume one kilowatt hour and the power company charges me 12 cents.

 

My conundrum is everyone brags LEDs use only 10-20 percent of the power required for old world incandescents.  With pixel trees you can't really compare them to simple LED or incandescent trees but... bottom line is pixel trees can consume considerable power even when they're off.  Hmmmmmmmmmmm.

 

Word to the wise if you have pixel trees: disconnect the power supplies when the show isn't running and save some money.

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41242 LEDS all on at 100%, draws about 8 amps. I used the EM100 Blue Water watt meter to check it out. I guess them pixies are not the energy saver that you would think.

Interesting,as when I calculate my wattage,I average 7 watts per string of 100 LEDs- so 41,242 LEDs would be 2887 watts { 24 amps} cant imagine what type LEDs you are using to have such low amperage? I am using full wave sealed strings from the vendors here.

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You know it is really interesting Chuck that you mention how big of a power hog they are. I replaced my incan mega tree (8 channels per color- red,green and white. 300 lights per channel) with a pixel tree. Had 24 vertical runs with 40 pixels per run. Also had a pixel star with 10 pixel modules in it. My wife is the "power bill watcher" each season. The bill came in....I thought that it would be lower. It was actually higher!  I never did any amp checks, but didn't see the occasional "pulse" on the lights I would sometimes see in the house from the incan mega tree. So I though I was doing good!  I see now why not ;-)

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A WS2812 strip that is 30 pixles to a meter, each pixel is 3 LEDs thats 90 LEDs. According to the mfr @ 5vdc full on (white) is 7.2 watts per meter, 36 watts per 5 meter strip. x 12 strips = 432 watts @ 5vdc. I never looked at the 120vac side.

 

Chuck on your trree you have 2720 pixels compared to my 1800 pixels. Are you reading the watts from the ac side?

 

These power supplies must be horrible.

 

I will check mine the next time I get them out.

 

Thanks for the great info!

 

Lee

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To further complicate things, something that draws 12 watts at 12 volts draws only 1 watt at 120 volts 

 

I always thoughts Watts were Watts no matter what. Am I wrong?

The way I understood it was if the bulb pulled 100w, you determined the amps it was pulling based on the voltage.

So how can something pull 12 watts at 12v and only 1 watt at 120v? Wouldn't the Watts be the same while the amps were changing?

 

Either way, I get what you're saying, I'm just trying to make sure I have it straight in my head as to which part I'm measuring.

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I always thoughts Watts were Watts no matter what. Am I wrong?

The way I understood it was if the bulb pulled 100w, you determined the amps it was pulling based on the voltage.

So how can something pull 12 watts at 12v and only 1 watt at 120v? Wouldn't the Watts be the same while the amps were changing?

 

Either way, I get what you're saying, I'm just trying to make sure I have it straight in my head as to which part I'm measuring.

You are indeed correct.  Watts and Volts have been used interchangably in error.  12 Watts at 12V would be 1 Amp at 12 Volts.  12 Watts at 120 Volts would be 0.1 Amps.  It is what Ohm's law is all about.  Voltage Current and Resistance share a relationship of Current = Voltage Divided by Resistance. Power is Volts X Amps.  By combining Power with Ohm's law Power can be calculated from any two components of Ohm's Law such as Resistance and Voltage, or Current and Voltage.

 

Ohm's law applies only to DC or AC only into a purely resistive load.  AC becomes slightly more complicated when inductors, transformers, and capacitors become involved.  Power Factor adds a component where Volts X Amps is greater than actual Watts, but that is beyond the scope of this forum except to mention when using an AC Wattmeter to measure AC current as above, current may read high due to something called reactive power and is not the same as actual Watts.  Google VARS (VoltAmpsReactive) and Power Factor for further study if interested.

 

If the above measurements do not have Reactive components, then 8 Amps at 120 volts would be 80 Amps at 12 Volts assuming no losses. Both would be 960 Watts.  Due to power supply effeciencies, the 12 Volt current would be less due to conversion loss and possible reactive power measured by the meter.

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I'm new so please forgive the double post.  A quick note on pixel power draw when off.  Even when off, pixel processors are still running at full speed taking brightness info of 8 bits for each color (24 bits) and sending all the remaining info down the string.  This does use some power.  Sorry about that.  A possible solution is to plug mega trees into a timer to power them down outside show hours. Even X10 or other power remote could be used, or a channel from a Renard or LOR box can operate a power relay for the pixel power supplies.  Be sure your solution pencils out.  A few KWH saved at 12 cents/KWH may not justify a $20 timer.

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Chuck,

 

I'm actually quite disappointed and surprised to see you present a post with such inaccurate information.  I've been apart of this forum for over 9 years and this is very uncharacteristic of you.  The problem I have with posts like this is that there are a ton of folks that don't know any better who will take your word on this, because, well, you're Chuck Smith.  99.9% of the time, I would take what you post in these forums as the way, the truth, and the light, because you're Chuck Smith.  That being said... I think your information is way off base and would like to present three concise, real-world examples coming from someone that has had a 20' incandescent megatree, a 20' LED megatree, and now a 20' pixel megatree.

 

1.  Incandescent:  I started small but at some point I went with red, green, and white on my 20' megatree.  12 channels of each color, but each color had 5 strings, so 60 strings of red, 60 of green, and 60 of white.  I did this because the base was 12' diameter, which is 240" and 60 strings meant one string every 7.5".  We all remember that the 100 count incan strings drew 0.3A @ 120V which, as others have pointed out, is 36W of power per string.  60 strings for each color = 2160W per color or 18A @ 120V with the entire tree lit either red, green, or white.

 

2.  LED:  I went with Creative Displays C6 LEDs for my megatree and went with the 70 LED strings that drew 7W each (AND were brighter than the 100 incandescent strings).  I stuck with 60 strings for each color.  60 strings x 7W = 420W per color with the tree lit either red, green, or white.  LEDs drawing only 19% the power of the "old world incandescents".  Now, one could argue that, I had fewer LEDs and the 19% isn't an apples to apples comparison, but I say fooey.  The LEDs were brighter than the incandescent strings AND drew less power.

 

3.  RGB Pixel:  I went with 48 strings of 50 count RGB pixels (5V DC WS2811) on my megatree.  My base string spacing went from 7.5" to closer to 10", but it still looks great... and once again... these RGB pixels are much brighter than even the 7W C6 LEDs, so less is not really less...  My real-world measurements on the pixel strings are as follows:  Each string of 50 draws around 0.8A @ 4.8V = 3.85W per string of 50 pixels and that is true for red, green, or blue.  When you go light the string pure white, because all of the R, G, and B LEDs have to illuminate, you get 1.7A @ 4.2V = 7W.  So, for most colors, you are drawing around 4W and for white, you are drawing 7W, per string of 50, which is brighter than a 70 count string of full wave C6 LEDs.  Per color that shows RGB Pixel drawing 185W which is only 9% of old world incandescent!  (again, pure white would be 420W, but if you're like me and like old-fashioned white, I run mostly red with a little bit of blue and green to create the RGB equivalent of incandescent white and I'm barely drawing 220W for my entire megatree).

 

Wrap-up:

 

Incandescent megatree draws 2200W (18A @ 120V) per color

C6 LED (full wave) megatree draws 420W (3.5A @ 120V) per color

WS2811 RGB Pixel megatree draws 185W (1.5A @ 120V) per color

 

That is just the megatree.  In my "old" display, I had 75,000 lights, mixed between LED and incandescent.  "All on" was 190A @ 120V, that I spread over 20 GFCI circuits, which I rarely did because the lights would dim in my house (we had 150A service which is 300A @ 120V).  That "all on" was bright, but I tell ya what... since switching my ENTIRE display to RGB nodes and pixels... I am only running 16,000 RGB "lights" and it is way brighter.  Anybody is welcome to check out my videos on Vimeo to see what I'm talking about... 16,000 RGB "lights" is brighter than 75,000 "old world" lights... and guess what?  I am running it off of FOUR circuits...

 

So, new display BRIGHTER, runs off four x 20A circuits

Old display, DIMMER, runs off the equivalent of 10 x 20A circuits

 

I will stick with my pixels.

 

"600-800 Watts, that's a lot of juice"  It really isn't... as I pointed out, my old megatree was over 2000W.

 

I really need to go measure the idle power draw of one of my pixel controllers.  I currently have all ten of my pixel controllers (mostly J1SYS p12S, but an e6804, some PixLite4 and PixLite16 controllers as well) running in the garage for testing (only have the 2400 megatree lights connected though).  I'd be surprised if each pixel controller draws 80 watts idle.  The only reason is, again, I have ten of them and they were on all December.  80 watts running 24 hours a day is around 2kWh per day, which is 60kWh for the month of December.  Here in Florida we pay a combined rate of around $0.10 per kWh, so that would be around $6 PER CONTROLLER of idle power consumption, $60 total... and I can tell you that my electric bill was not that high.  If you factor in 4 hours per night of roughly 2500W power consumption for the lights, that is another 10kWh per day, 300kWh for the month, and that is $30 on the electric bill...

 

Again, the reason for my post is that, I hate misinformation.  There are far too many gullible people on the internet that read this stuff and then believe that it is true and then they are immediately starting off on the wrong foot as the saying goes...  You have done so much over the years to HELP people get off on the RIGHT foot.  I am one of them.  I would at least delete (or edit) your paragraph that states that 12 watts at 12 volts is only 1 watt at 120 volts...

 

Hopefully folks will understand the tone with which I am trying to deliver this message.  I have the UTMOST respect for you, Chuck, and for what you have done.  This thread is just not right...

 

Sincerely,

 

-Louie

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Interesting,as when I calculate my wattage,I average 7 watts per string of 100 LEDs- so 41,242 LEDs would be 2887 watts { 24 amps} cant imagine what type LEDs you are using to have such low amperage? I am using full wave sealed strings from the vendors here.

I know. I also have plugged many in line before and their draw was minimal. I have a mixture of full and half waves. To top it all, my whole setup including a LED projector, is all on one regualr household circuit with a regular on/off wall switch. When I get to 200000+ lights, it will be a different story.

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I think the information is very helpful.  Not to pick at the detail, but at the high level idea that pixel "gear" consumes far more power than what I thought.  Using a kilowatt I did a test.

 

  • Power Supply with no fan         + 5-7 watts  7
  • + Fan to power supply              + 6 watts    13
  • + Falcon 16 pixelnet Hub          + 6 watts    19
  • + 50 ws2811 12v nodes (off)    + 2 watts     21
  •        with Falcon uSC string Controller

21 watts at idle.

 

It showed me that:

  • DC power supplies use power even when they are idle
  • Controllers use power when idle
  • Pixels use power when off

So maybe those 32 20 amp GFCI outlets I have will still get used even when I'm almost converted to all LED's. :)

 

Thanks for turning the light on with pixels.

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You might want to go measure your cable box or dish box, Jeff... it most likely draws 21 watts, even when off... and that runs 12 months a year... and most houses have more than one box.

You can sell those GFI breakers on eBay... every 1200 pixels will run on a 350w power supply that draws 3 amps at 120v. That means 6000 pixels on a single 20 amp circuit (drawing 15 amps to obey the 80% rule). Most folks won't need more than four circuits (that would be 24,000 pixels!). I'm not even utilizing all four of my circuits with 16,000 pixels...

Louie

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You might want to go measure your cable box or dish box, Jeff... it most likely draws 21 watts, even when off... and that runs 12 months a year... and most houses have more than one box.

You can sell those GFI breakers on eBay... every 1200 pixels will run on a 350w power supply that draws 3 amps at 120v. That means 6000 pixels on a single 20 amp circuit (drawing 15 amps to obey the 80% rule). Most folks won't need more than four circuits (that would be 24,000 pixels!). I'm not even utilizing all four of my circuits with 16,000 pixels...

Louie

"350 watt power supply that draws 3 amps"..........you are assuming that power supply is 100% efficient,but it is not! plug that power supply into a "kill a watt" meter and load it up with 350 watts of pixel load and look at the meter reading.......you most likely will be surprised!

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Agreed, but nobody would actually even run the 350 watt power supply full bore... So 3 amps is very fair. I do have my megatree connected on the ceiling of my garage and can run that test with the kilawatt to get real numbers. I already know the wattage that the strings draw on the DC side.

Louie

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Hey all,

 

I just thought I would post back in now that I received my Kill-A-Watt and made some measurements.  I was posting this info in a thread on another forum and remembered that I wanted to post this hear as well...

I finally got my Kill-A-Watt the other day and went out to do some testing.  As I think I mentioned earlier, I am interested in leaving my ten e1.31 controllers plugged in and running in the garage this summer so that I can experiment with (1) new software (2) Falcon Pi Player (FPP) master / slave setup (3) music sequencing in general.  I have convinced myself that I don't need all the lights plugged in to see data issues, just all the controllers that will get data.  I do, however, have the megatree (which lives on my garage ceiling) plugged in for visual reference.  That megatree consist of 48 poles with 50 ws2811 pixels each (square, flat back style) = 2400 lights.

So, I went off to the garage with my new Kill-A-Watt in hand...  Since the megatree is spread over two p12s controllers, each in its own case with a 350W power supply, I went to my controller rack that I just built and plugged two p12s controllers to the Kill-A-Watt, each p12s in its own case with its own 350W power supply, but NO LIGHTS connected.  The power draw was 11W total for both controllers.  I then went and connected the Kill-A-Watt up to the two p12s controllers that have the 2400 megatree lights plugged into them and the power draw was 24W total (lights off).  I went and flipped on a little sequence I have running on the FPP (link below) and the power went to between around 190W to 375W max.  Basically, the 190W was when there was red sweeping going on and the 375W was when there was a much higher percentage of white (duh).  That kind of confirms what I proposed in my original post int his thread.  190W for the entire tree lit-up in any of the "colors", closer to 400W for pure white.... probably around 250W if I "make" warm white with the pixels.

https://vimeo.com/120250250

Summary:

two x p12s controllers, no lights:  11W
two x p12s controllers, 2400 lights OFF:  24W
two x p12s controllers, 2400 lights ON:  190W to 375W

For further reference, I connected a wifi router, a gigabit switch, and the FPP to the power switch with the two p12s controllers without lights and the total power draw of the whole shabang was only 21W... right now, I'm figuring (need to confirm) that all of the e131 controllers running (no lights), the two p12s controllers with lights (lights OFF) and the network stuff listed above will take around 75W.  If I end up leaving that on all the time, it will use around $5.40 electricity per month.

-Louie

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Chuck is right, powering strings of conventional LED lights has less power wasted as heat than pixel lighting. The two main causes of the excess power consumption of pixel lighting are:

 

1. The switchmode power supplies commonly used to supply the power to pixel lights typically have a power factor of around .65 unless its an expensive unit with power factor correction. This means that a power supply providing 400 Watts of output actually consumes 615.4 VA (Volt-Amperes) which is 5.13 Amps at 120 Volts. In contrast, 400 watts worth of mini lights would consume 3.33 Amps at 120 Volts because they are a purely resistive load with a power factor of 1.0. This is also one of the dirty little secrets about the compact fluorescent bulbs. There is a tiny switchmode power supply in the base (do you ever notice how warm the base of these lights gets?) that uses more VA than Watts of power because the power factor is less than 1.0. 

 

2. The fact that strings or ribbons of pixel lights are using low voltage to feed each pixel in parallel causes power loss due to voltage drop in the actual pixel string wire. That's why pixel strings are limited in their length while you can run hundreds of feet of conventional LED Christmas lights, because there is 120 volts running through the conventional string and the LED's are wired in series which reduces the current to 1/20th of that running through a 6 volt pixel string.

This is why utility companies use very high voltages so they can lower the current in amperes flowing through the wires to reduce power loss when they transmit electrical energy for long distances.

 

One other thing that is very minor but also counts, is the amount of computer processing power required to turn on and off thousands of individual pixels. More processing power equals faster and hotter CPU's and more RAM which also sucks more juice!

 

In the end though, pixel lighting as awesome, so put another shovel of coal in that boiler and hit the switch!

 

lor_176_lightgray_none.gif

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I still stick by my assertion that, about the only thing "right" in the first post of this thread is that "unplug your controllers when they're not being used to save money".  That is an accurate statement, however, that amount of saved money is around $5 and I am asking, do you run around unplugging your cable or satellite box when it isn't in use?  Even when that thing is "off", it is drawing the same wattage as a couple of pixel controllers... and you leave those running all year 'round.

 

You have brought up an excellent point in the VA versus Watt discussion and I went back and checked... the Kill-A-Watt incorrectly lists Wattage not as Volts x Amps... but as the Wattage drawn without power factor accounted for.  I apologize.  THAT being said, the numbers still work out in favor of pixels and that is the underlying message I am trying to get across.  If you go back to my lengthy first post in this thread, I had the following set of data:

 

Incandescent megatree draws 2200W (18A @ 120V) per color

C6 LED (full wave) megatree draws 420W (3.5A @ 120V) per color

WS2811 RGB Pixel megatree draws 185W (1.5A @ 120V) per color

 

If you adjust the WS2811 pixel line for power factor (I took your 0.65 value, although my power supplies appear to be running closer to 0.70 as measured in V-A on the Kill-A-Watt), the data becomes:

 

Incandescent megatree draws 2200W (18A @ 120V) per color

C6 LED (full wave) megatree draws 420W (3.5A @ 120V) per color

WS2811 RGB Pixel megatree draws 284W (2.4A @ 120V) per color

 

As you can see, the pixel tree (for colors, not pure white) is still the leader / winner out of the three technologies, providing you an ENERGY SAVINGS of 32% over conventional LEDs and an ENERGY SAVINGS of 87% over incandescent.  That solidifies my position in this thread.  As I said above, I forgot to account for power factor (actually thinking that the Kill-A-Watt would show you proper wattage), but even with it included, the pixels are still a better option.

 

I'd like to mention something about the "processing power required to turn the pixels on and off" comment you made.  I'm not sure how much the Falcon Pi Player is mentioned around these parts (being a member of DIY Christmas forum, Falcon Pi Christmas forum, Aussie Lights Christmas forum, Light-O-Rama forum, Nutcracker forum, and Light Show Pro forum has its benefits).  As you may have seen in my one thread above, my Kill-A-Watt measurements included a blurb about the power drawn by a thing called the Falcon Pi Player or FPP for short.  Everybody here interested in pixels should really take a look at this thing.  It is crazy simple to operate (it runs off Linux and a Raspberry Pi unit, but you don't ever "see" the Linux in setting it up).  So far, they have demonstrated the ability to run something crazy like 20,000 pixels off of the thing... which by the way only costs around $55-60 to build one... much less than a computer... and power draw?  Around 7W to run... shoot, when I was an old fashioned incandescent and LED guy with 12 LOR controllers, I needed a P4 running probably around 100W!!  So, message is short and sweet, go read about the Falcon Pi Player (FPP for short) and you will see as 100's of others have seen that the modern day running of Christmas lights is getting MORE power efficient than it ever has been, not less....

 

As I said above, the right information needs to be understood.  If anybody has any question, please let me know.  Also, Mike, thanks for bringing up the power factor because I had completely forgotten about it.  One last comment about DC switching power supplies, as I said, my cheapie Chinese supplies are looking like they are around 70% efficient... doing a Google search, common Meanwell power supplies are around 78% efficient and the higher end Meanwell power supplies can be had that are up to 90% efficient... the problem is, the 70% efficient model costs $23 for 350W, the 78% efficient model costs $45 for 350W and the 90% efficient model costs $84 for 300W... so one has to pick their battle... If I assume the largest impact of efficiency is when the show is running, one power supply might waste $3 extra of electricity in a show season due to ineffiency:   200W / 0.7 = 285W - 200W = 85W x 5 hours in an evening show = 425W-hr x 60 days in one show season = 25.5kW-hr x $0.10 per kW-hr = $2.50.  If you went with the higher end power supply for quadruple the cost, you can reduce that waste from 70% to 90% and save yourself $2.50 - $0.83 = $1.67 which is obviously not worth it.

 

Take care.  I hope this information is useful in helping someone understand the power of pixels.

 

-Louie

 

Chuck is right, powering strings of conventional LED lights has less power wasted as heat than pixel lighting.  The two main causes of the excess power consumption of pixel lighting are:

 

1. The switchmode power supplies commonly used to supply the power to pixel lights typically have a power factor of around .65 unless its an expensive unit with power factor correction. This means that a power supply providing 400 Watts of output actually consumes 615.4 VA (Volt-Amperes) which is 5.13 Amps at 120 Volts. In contrast, 400 watts worth of mini lights would consume 3.33 Amps at 120 Volts because they are a purely resistive load with a power factor of 1.0. This is also one of the dirty little secrets about the compact fluorescent bulbs. There is a tiny switchmode power supply in the base (do you ever notice how warm the base of these lights gets?) that uses more VA than Watts of power because the power factor is less than 1.0. 

 

2. The fact that strings or ribbons of pixel lights are using low voltage to feed each pixel in parallel causes power loss due to voltage drop in the actual pixel string wire. That's why pixel strings are limited in their length while you can run hundreds of feet of conventional LED Christmas lights, because there is 120 volts running through the conventional string and the LED's are wired in series which reduces the current to 1/20th of that running through a 6 volt pixel string.

This is why utility companies use very high voltages so they can lower the current in amperes flowing through the wires to reduce power loss when they transmit electrical energy for long distances.

 

One other thing that is very minor but also counts, is the amount of computer processing power required to turn on and off thousands of individual pixels. More processing power equals faster and hotter CPU's and more RAM which also sucks more juice!

 

In the end though, pixel lighting as awesome, so put another shovel of coal in that boiler and hit the switch!

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Someone was nice enough to do a power draw experiment which includes fully loaded stress test and idle.  To see where the power is used, he uses real time FLIR video.  Well worth viewing.

 

In summary, a new Pi runs under .3 Amps DC at 5V or less than 2 Watts.  7 Watts is over 1 Amp at 5V so a USB power hog must be attached to use that much.

 

I run my FPP on a 5V 0.7A phone charger with no problems.  I'm not using USB, only E1.31.

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