nutz4lights
Full time elf
Hey all,
This has been on my mind so I figured I would pose the question here. I plan on making some measurements later today, but figured I'd get the thread started. This is based on my recent discovery that the Technicolor 12V pixels actually draw 0.6W per pixel even though the spec sheet states 0.3W. My original plan was to run 150 of these from a single output of a p12s injecting power with a "tee" setup between pixel 100 & 101. I figured, 0.3W per pixel is 30W for 100 @ 12V = 2.5A out of the controller and then another 1/2 that (50 pixels) injected at pixel 100/101. Now that I know these are 0.6W per pixel, that means 60W going out of the controller, which is 5A (a perfectly fine value on my p12S, but not quite so good on an e6804 which is fused at 5A)...
So, I got to thinking... what really happens to the power draw out of a controller when you inject power? On my megatree this year, I ran a 50 pixel string up and another 50 pixel string down, supplying power and data at pixel 1 and then just injecting power at pixel 100. I never bothered to measure the current draw on that power injection line, or the line out of the controller for that matter. So let's say I would have done that megatree without power injection. Those were 5V 2811 pixels rated at 0.3W per pixel. 100 pixels off one output would have been 30W and subsequently 6A of power draw. Six outputs would have been 36A on one bank of the p12s controller which would have blown the 30A fuse. That didn't happen, so obviously, by injecting power at pixel 100, I also have pulled some of the current load off of the controller. I am passing current into the 100 pixel string from the pixel 1 direction out of the controller and then from the pixel 100 direction direct from the power supply.
My curiosity is, do the two legs supply equal current? That would be 50 pixels @ 0.3W per pixel = 15W which is 3A at 5V... and for 6 outputs on the p12s that would have totaled 18A... much more reasonable, and another 18A direct out of the power supply. To be completely fair, I have measured the current draw on those 5V pixels already and only saw 1.4A of current draw for 50 (didn't measure the 100 pixel setup).
Now back to the more interesting scenario (currently). What happens to power draw when you inject between pixel 100 & 101 of a 150 pixel string? If the current draw on a 100 pixel string flows current back into the string from the pixel 100 direction, then theoretically injecting in between pixel 100 & 101 of a 150 pixel string would probably flow current back into the 100 pixel section of the string AND into the pixel 101-150 section of the string on that injection line. So, the controller would output 50 x 0.6W = 30W which at 12V is 2.5A (or closer to 3A using my 10.5V setting on the power supply) and then the injection line would be responsible for providing power to 100 pixels (100-50 & 101-150). That injection line should be carrying 100 x 0.6W = 60W which is 5A at 12V (or closer to 6A using my 10.5V setting on the power supply).
So, does this all make sense? Like I said, I will try to get some good measurements here today and post an update. I am curious what others thoughts are on the subject. I don't know that I've ever seen a post covering this topic before... feel free to link one here if you know of one.
Thanks for looking.
-Louie
This has been on my mind so I figured I would pose the question here. I plan on making some measurements later today, but figured I'd get the thread started. This is based on my recent discovery that the Technicolor 12V pixels actually draw 0.6W per pixel even though the spec sheet states 0.3W. My original plan was to run 150 of these from a single output of a p12s injecting power with a "tee" setup between pixel 100 & 101. I figured, 0.3W per pixel is 30W for 100 @ 12V = 2.5A out of the controller and then another 1/2 that (50 pixels) injected at pixel 100/101. Now that I know these are 0.6W per pixel, that means 60W going out of the controller, which is 5A (a perfectly fine value on my p12S, but not quite so good on an e6804 which is fused at 5A)...
So, I got to thinking... what really happens to the power draw out of a controller when you inject power? On my megatree this year, I ran a 50 pixel string up and another 50 pixel string down, supplying power and data at pixel 1 and then just injecting power at pixel 100. I never bothered to measure the current draw on that power injection line, or the line out of the controller for that matter. So let's say I would have done that megatree without power injection. Those were 5V 2811 pixels rated at 0.3W per pixel. 100 pixels off one output would have been 30W and subsequently 6A of power draw. Six outputs would have been 36A on one bank of the p12s controller which would have blown the 30A fuse. That didn't happen, so obviously, by injecting power at pixel 100, I also have pulled some of the current load off of the controller. I am passing current into the 100 pixel string from the pixel 1 direction out of the controller and then from the pixel 100 direction direct from the power supply.
My curiosity is, do the two legs supply equal current? That would be 50 pixels @ 0.3W per pixel = 15W which is 3A at 5V... and for 6 outputs on the p12s that would have totaled 18A... much more reasonable, and another 18A direct out of the power supply. To be completely fair, I have measured the current draw on those 5V pixels already and only saw 1.4A of current draw for 50 (didn't measure the 100 pixel setup).
Now back to the more interesting scenario (currently). What happens to power draw when you inject between pixel 100 & 101 of a 150 pixel string? If the current draw on a 100 pixel string flows current back into the string from the pixel 100 direction, then theoretically injecting in between pixel 100 & 101 of a 150 pixel string would probably flow current back into the 100 pixel section of the string AND into the pixel 101-150 section of the string on that injection line. So, the controller would output 50 x 0.6W = 30W which at 12V is 2.5A (or closer to 3A using my 10.5V setting on the power supply) and then the injection line would be responsible for providing power to 100 pixels (100-50 & 101-150). That injection line should be carrying 100 x 0.6W = 60W which is 5A at 12V (or closer to 6A using my 10.5V setting on the power supply).
So, does this all make sense? Like I said, I will try to get some good measurements here today and post an update. I am curious what others thoughts are on the subject. I don't know that I've ever seen a post covering this topic before... feel free to link one here if you know of one.
Thanks for looking.
-Louie