Author Topic: Roofline flickers when white  (Read 1943 times)

Offline Scottishsurfer

  • Jr. Member
  • **
  • Join Date: Mar 2016
  • Location: Rancho Santa Margarita, CA
  • Posts: 60
  • Kudos: 0
    • My light show website
Roofline flickers when white
« on: January 03, 2017, 06:37:37 PM »

Hi guys - in the attached video, you can see my roofline flickers when fully white.  Some folks have stated that I need power injection, but would I not see that?  EG: Pixels at the end of the string would be yellow?  I don't mind injecting power at the end of the string, but will that fix my issue?


Others have stated it could be the length of my run from controller to first pixel being 70 feet; however, my Spinners also had 60-70 feet of cable between them and the controller with no issue.


One other possible cause, overloading the power supply when I make all the pixels white.  I'm running all my pixels from an Alphapix16, and my 120volt lights from a Sandisk ssr via gpio from my PI.  I'd love to hear if anyone else figured out how to stop flashing pixels.  Thanks, Colin


https://vimeo.com/197737791

Offline Ebuechner

  • Sr. Member
  • ****
  • Join Date: Apr 2016
  • Location: Madison WI
  • Posts: 316
  • Kudos: 10
Re: Roofline flickers when white
« Reply #1 on: January 03, 2017, 07:40:48 PM »
I'm going to say the same thing everyone else did you're going to need more power. 70 feet is too long to run the power and expect it to work without power injection. I would put a small power supply near the beginning of the strip to run that strip only. When your strip goes full White you're putting resistance on both the positive and negative and your negative is your return path for your data

Offline JonB256

  • Supporting Member
  • ******
  • Join Date: Mar 2013
  • Location: Granbury, Texas
  • Posts: 5,293
  • Kudos: 126
    • Granbury Christmas Lights
Re: Roofline flickers when white
« Reply #2 on: January 03, 2017, 08:05:27 PM »
That 70 foot run of wire to the first pixel could be "eating" as much as 2 volts when you go full white. Power injection at the end should fix the problem.

Most 12v pixel strings will be fine until the voltage drops into the 9v range. If you put that string on full white and measure voltage at the first pixel and at the last pixel, my bet is first pixel voltage is 10v and last pixel is closer to 8v.

DON'T try raising the voltage though. That will just make it too high for anything but full white.

Offline zwiller

  • Falcon Beta Team
  • **
  • Join Date: Mar 2013
  • Location: Sandusky, OH
  • Posts: 994
  • Kudos: 13
Re: Roofline flickers when white
« Reply #3 on: January 04, 2017, 06:50:51 AM »
I am with the rest, power injection.  First off, low voltage across pixels does not act the way you'd expect (yellow pixels near end of string).  The behavior is erratic and not really predictable.  IMO the whole string is usually affected and acts up, freezing, act slow, wrong colors and in your case flicker.  There are 2 levels of power.  1 is enough power to run accurately (no flicker) and another to ensure proper color rendition.  In other words, just because you are not having flicker does not mean the pixels are receiving the proper amount of power and providing the best color.  Getting proper power to pixels is a balancing act.  All depends on wire gauge/power supply/distance/# of pixels/even the type of pixel.  IE the reason your spinners were not affected is perhaps they are made of strips.  Strips seem to be more forgiving, maybe since there's no wire, that's my guess.  70' IS long.  I plan to test this extensively, but so far I have seen a pattern with long distances.  Folks using the china 3 wire for hookups are having the most issues.  Folks using cat5 are mostly OK but a few that had problems but that was resolved when using true 18g hookup.  There are some folks happy with cat5e/6 as well.  In looking at your layout I can't help but wonder if the reason you are running 70' is because you are light on controllers.  My layout is similar to yours and I run 6 controllers.  I think a few more controllers and you can cut your distances is half easily and the issue should go right away.  You'll have alot of flexibility and room for expansion in the future.  Alternately, power injection would work or running 18g as well. 
Sam
 Last year's video: https://vimeo.com/150560653

Offline Gilrock

  • Sr. Member
  • ****
  • Join Date: Dec 2013
  • Location:
  • Posts: 329
  • Kudos: 8
Re: Roofline flickers when white
« Reply #4 on: January 04, 2017, 08:23:17 AM »
I solved a couple issues like this in my display by wiring in a null pixel halfway to the first pixel.  I had runs where I had to add power injection in the middle.  And I sometimes had to reduce the max power for the output.  I ran most of my display with the Falcon outputs set to 50% and it was still plenty bright and had better color.  You just need to try all these ideas to figure out what works.

Offline markrvp

  • Full Member
  • ***
  • Join Date: Dec 2015
  • Location: Mansfield, TX
  • Posts: 124
  • Kudos: 7
Re: Roofline flickers when white
« Reply #5 on: January 04, 2017, 12:51:29 PM »
In two different displays I did this year, I experienced a similar problem on 3 different props, and all three were different issues requiring different solutions.


Prop 1:  A long run from the controller into a Tee caused the signal to be weakened when the signal and power were combined in the Tee.  Solution was to remove the data pin from the power injection cable. 


Prop 2:  A bad pixel caused all the pixels after it to flicker when all white.  Did not present on any other color.  Solution:  Replace bad pixel (replaced four pixels, 2 before issue and 2 after issue)


Prop 3:  Bad ground connection.  Problem only presented when all white.  Solution:  Resoldered ground connection


Notice that a lack of power wasn't the issue on any of those props. 


On your display, I'm guessing there is a problem in the wiring between the two sections of roof.  You see the whole section flicker which is a pretty good indicator where to start looking for the problem.  It could be the problem is the signal is too weak to go that far cleanly.   How long is the wire between those two sections?  I tend to agree with you that if it were strictly a power problem, you would see the lights at the end of the run turn yellow to red.


Having said that, 60' to start the run is a problem in and of itself.  If it were me, I'd add a uAmp or RobG's board that cleans the signal right at the SPI output.  If that doesn't fix it, I'd add a null pixel in the wire between the two sections of roof.   Or you can try adding power and see if that helps. 

Offline Scottishsurfer

  • Jr. Member
  • **
  • Join Date: Mar 2016
  • Location: Rancho Santa Margarita, CA
  • Posts: 60
  • Kudos: 0
    • My light show website
Re: Roofline flickers when white
« Reply #6 on: January 04, 2017, 08:15:11 PM »
I knew folks on this board would be the gurus. I think my best course of action is to just buy another board and place it near the roofline next year.  Just because a board provides 16 outputs does not mean you have to run your entire show from one controller. Live and learn.

I will test with a shorter run and post back to this thread so we can all learn. Had the end of my pixels been yellow it would've been nice and simple.

Zwiller -  I think you're onto something with the pixel strips requiring less power which is why they work. 

Huge thank you everyone.

Offline corey872

  • Supporting Member
  • ******
  • Join Date: Oct 2013
  • Location:
  • Posts: 490
  • Kudos: 16
    • Link to the sale...
Re: Roofline flickers when white
« Reply #7 on: January 04, 2017, 09:48:31 PM »
Not trying to be a jerk and I don't know any better way to say it, but 'yellow pixels' don't really mean anything.  I would not expect pixels to turn yellow based on low voltage... perhaps this is a thought based on an incandescent bulb burning bright white at recommended voltage then turning yellow, orange and finally red at lower voltage?  But for LEDs it would mean the red and green LEDs are firing, but not the blue.... that just doesn't happen for any 'known' reasons.

Typically what I've seen:

White flickering - voltage drop issues or low voltage - Power supply can not support full volt/current output when all LEDs in all nodes are on full bright to make the 'white'.

White lock-up - grounding issue - Just as you get 'voltage drop' on the power line, you can get 'ground line loading' on the ground wire.  The 'local' ground at the pixel can float up in voltage.  Once it approaches 1.5V, the node 'thinks' the 5 volt data signal is actually swinging from +3.5V to -1.5V.  If the node does note see the signal reach the 3.5V level, the node can not 'read' it.  So the nodes switch white, load the ground line with excess power and then they can not read any more data...stuck on white.

Rainbow flickering - weak data - We noticed this a lot with the older 'SSC' boards from DIYLA as they were only capable of sending data a few feet - or in some cases, only a few inches before it would become 'corrupt'.  With corrupt data random colors propagate through the string and create a rainbow instead of the intended colors.

Some nodes on dim red when they should be off - over voltage - I suspect this has to do with current leaking through the gate of the control chip.  Typically green and blue LEDs drop around 2.8 - 3.2V, but red drops only ~1.8-2.0V.  So if you send 12V, the control chip has to 'shut off' the remaining ~9V on the green/blue LEDs, and 10V+ on the red.  If that 10V happens to be right at the limit for the control chip, some current can leak through the gate and make the red LED dimly light even though it is supposed to be off.  In most instances, backing the voltage down to ~11.8V at the nodes reportedly cures this.

You could test your issue by simply dimming the LEDs or commanding a few to be off.  This would lessen the power draw and if it fixes the issue, it would prove the nodes are not getting enough power.  An increase in power supply voltage (if adjustable), bigger wire, power injection, or a shorter run may fix the issue.

You also mention your spinners don't suffer the same issue.  Though to be a valid comparison, you'd need to have spinners on exact same power supply, exact same distance and the same number of nodes on a spinner as the roof outline.  If you have fewer pixels on a spinner, then the power draw is not the same.  If they are on a different power supply, then the supplied voltage may not be the same.  It could even be an issue of the spinners being even slightly closer to the supply and the flickering roof reduces the power just enough that the spinners can work fine.  In that case it would be like having a balance with 100.00 pounds on one side and 100.01 pounds on the other.  the 100.01 pound side would always fall, but the issue is not the overall weight, just the imbalance.

Anyway, hope this helps!  :)
Corey
 2018 uSC, Afterburner, uAmp co-op - pending May-June 2018.  Remaining boards are now FOR SALE

Offline zwiller

  • Falcon Beta Team
  • **
  • Join Date: Mar 2013
  • Location: Sandusky, OH
  • Posts: 994
  • Kudos: 13
Re: Roofline flickers when white
« Reply #8 on: January 05, 2017, 05:20:38 AM »
I think my best course of action is to just buy another board and place it near the roofline next year.

Careful with that.  I've read that does not work well for others.  There is usually last minute tinkering and last thing you want is to drag the ladder out...  Also potentially dangerous: last minute rushing and fall off.  I place my house controllers at the bottom near the sides of the house and run up from there.  I run to the roof and its a 2 story home and have plenty of slack wire and my wire is only 25' long.  Also, at first you have a tendency to run all wiring to one side because you worried about your sequence and channel programming, but once you get more comfortable and understand it, you realize you can do some pretty crazy things.  IE my roofline is actually 2 sections being fed from opposite sides when setup in my sequencer (LSP) it's all one line.  Also, all my windows are 2 ports/lines and not one. 

I don't think you'll find a better explanation of the various issues we have with pixels than what Cory posted.  That's wiki material if you ask me! 

Offline Scottishsurfer

  • Jr. Member
  • **
  • Join Date: Mar 2016
  • Location: Rancho Santa Margarita, CA
  • Posts: 60
  • Kudos: 0
    • My light show website
Re: Roofline flickers when white
« Reply #9 on: January 15, 2017, 05:17:34 PM »
Cory - thank you for taking the time to give such a detailed response.  I tried a couple things based on your suggestions. Here's what I discovered.

When I disconnect everything from the controller except the roofline, it worked perfectly. Even with my 65 foot cable (16 gauge from controller to first pixel). So for next year I am going to put the roofline on it's own power supply. (Probably controller and power supply) and make sure my cable run is less than 40 feet.

I think I was getting confused with folks saying I should see yellow pixels if not enough power. That kind of sent me down a rabbit hole. Now I fully understand what happened. I was lucky with the massive cable run (I was kind of asking for trouble) but the real reason I got flicker was because I was pushing way too many pixels with one power supply. When everything went all white, I bet I was overloading the power supply.

Thanks to everyone on this board helping. I hope this post assists others in the future.

Offline Gary

  • Supporting Member
  • ******
  • Join Date: Jan 2015
  • Location: Chilliwack, BC Canada
  • Posts: 380
  • Kudos: 3
    • Diamond Crescent Musical Christmas Lights
Re: Roofline flickers when white
« Reply #10 on: January 17, 2017, 12:44:06 AM »
When I disconnect everything from the controller except the roofline, it worked perfectly. Even with my 65 foot cable (16 gauge from controller to first pixel). So for next year I am going to put the roofline on it's own power supply. (Probably controller and power supply) and make sure my cable run is less than 40 feet.

I think I was getting confused with folks saying I should see yellow pixels if not enough power. That kind of sent me down a rabbit hole. Now I fully understand what happened. I was lucky with the massive cable run (I was kind of asking for trouble) but the real reason I got flicker was because I was pushing way too many pixels with one power supply. When everything went all white, I bet I was overloading the power supply.

From the sounds of it, you're running one power supply? For my controllers with more pixels on them, I have two power supplies hooked up--one for ports 1-8 and another for ports 9-16.

Offline Scottishsurfer

  • Jr. Member
  • **
  • Join Date: Mar 2016
  • Location: Rancho Santa Margarita, CA
  • Posts: 60
  • Kudos: 0
    • My light show website
Re: Roofline flickers when white
« Reply #11 on: February 06, 2017, 11:27:57 PM »
Just wanted to post what I uncovered when I started taking down my display.


I disconnected all display elements except for my roofline, and guess what, everything ran perfectly.  My issue was that I was trying to drive my entire show from just two power supplies.  One power supply was connected to an alphapix 4 running 2 models (composed of 2 strips) and then everything else from my alphapix 16.  Roofline, Garage Door outline, 2 pixel stars, 3 arches and 10 mini candy canes.  When I started adding up all the amps, wow - I'm amazed anything worked when all white :)


This was my first year doing pixels, but I learnt a ton.  I think power injection is just a little scary for newbies, but essential for a stable show.  Either break it up (more pixel controllers/power supply combinations) or power injection.


Huge thank you to everyone on the board who helped me troubleshoot (and uncover the root cause) of my flickering roofline.  I hope this helps others in the future.

 

Back to top