Author Topic: Two power supplies at different voltages?  (Read 736 times)

Offline Gary

  • Supporting Member
  • ******
  • Join Date: Jan 2015
  • Location: Chilliwack, BC Canada
  • Posts: 313
  • Kudos: 3
    • Diamond Crescent Musical Christmas Lights
Two power supplies at different voltages?
« on: October 02, 2016, 11:47:42 PM »
The pixels that I have are from 2015, and apparently there was an issue with the WS2811 IC on them where they are sensitive to over voltage (i.e. over 11.8V) and under certain situations, caused some weird issues with stray pixels remaining red when they are supposed to be black.

My question is: I suppose that if I have two power supplies on My F-16 V1, I can have outputs 1-8 on 11.8V, but for my longer runs on outputs 9-16, I can have 12V, and the voltage drop will make them call in the 11.8-ish range? I suppose the answer is yes, but I'd also like to clarify if the circuitry on the board is powered by power input 1 or 2 (so I don't crank up the voltage too much on the power supply powering the circuitry side).

And I suppose the same goes for the F16-B as well?

Offline AAH

  • Hero Member
  • *****
  • Join Date: Jul 2014
  • Location: Australia
  • Posts: 500
  • Kudos: 14
  • Blinky blinky blinky
    • I love blinky lights
Re: Two power supplies at different voltages?
« Reply #1 on: October 03, 2016, 12:35:26 AM »
At "no load" there will be no voltage drop so the pixels that have the problems with 12V will still see 12V rather than 11.8V. Better to have the power supplies closer to the pixels or use heavier power cable. Bumping up the voltage and relying on a voltage drop that only occurs at heavy load won't fix your problem.
You can call me AAH, you can call me Al, or you can call me Alan.
http://www.hansonelectronics.com.au/wp-content/uploads/Catalogue.pdf Catalogue of my blinky bits
http://www.hansonelectronics.com.au/

Offline Gary

  • Supporting Member
  • ******
  • Join Date: Jan 2015
  • Location: Chilliwack, BC Canada
  • Posts: 313
  • Kudos: 3
    • Diamond Crescent Musical Christmas Lights
Re: Two power supplies at different voltages?
« Reply #2 on: October 03, 2016, 11:50:02 PM »
I did some experiments a month or so back where I was checking the voltage at the beginning, middle, and end of a sample pixel string and looking back at the notes I made, I was losing about 2V at the first pixel after 50 ft of CAT5. The pixels were only showing the flickering problems when they were on high white (at least about 80% brightness), so I don't know if when you referring to as "no load", that meant a 0,0,0 RGB value?.


If turning up the voltage a wee bit doesn't work, I have a trick in mind for my one potentially problematic string at the end of my longest CAT5 cable by using an extra CAT5 cable (essentially reducing the wire gauge) that's used for a "hot spare" pixel string in case I have a pixel malfunction but I don't want to go up on the roof to fix it. I did as test of doubling-up two long CAT5 cables for power, and it reduced the voltage drop by +0.6V, and it made my flickering problems go away.


...But I was still wondering about what each power input energizes on the boards.

Offline Phrog30

  • Sr. Member
  • ****
  • Join Date: May 2015
  • Location:
  • Posts: 388
  • Kudos: 8
Re: Two power supplies at different voltages?
« Reply #3 on: October 04, 2016, 05:07:15 AM »
You will have voltage drop from the wire and the pixels even if they aren't on, not sure what aah is talking about.

Sent from my SM-G900V using Tapatalk

Offline pixelpuppy

  • Sr. Member
  • ****
  • Join Date: Aug 2015
  • Location: Dallas, TX
  • Posts: 492
  • Kudos: 10
Re: Two power supplies at different voltages?
« Reply #4 on: October 04, 2016, 11:46:19 AM »
Voltage drop is a function of Current and Resistance. I think AAH is simply saying if there is no current then there is no voltage drop.
 
Pixels that have power but not lit are still drawing current.  So having pixels just connected to power will be a small "load" and there will be some voltage drop with pixels powered but not lit.  Its not a heavy load, but still some current and some voltage drop.  Setting them to full white will be a full load and draw the most current and have a larger voltage drop.
Vixen and xLights for sequencing / FPP for scheduling and playing / Falcon controllers for pixels / DIY controllers for everything else

 

Back to top