Author Topic: WS2811 IC voltage drop tolerance  (Read 1066 times)

Offline Emuney18

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WS2811 IC voltage drop tolerance
« on: January 19, 2017, 06:13:53 AM »
So I did a test last night to see how far my power supply could be located from my Falcon differential receiver board. I got some interesting results. Here is the setup.
12V ws2811 pixels running off the diff receiver each pulling 28 mA.
96 pixels on 3 outlets so 294 pixels
Power to the board is from 20' of 18 awg spt wire
Sequence where lights are static on all white.
With the lights output set to 50% in the Falcon hardware I get a starting voltage of 9.68 volts at the board when the lights are on. The voltage at the end of the strings was some where around 8v I don't remember.  There was no noticeable change in the white color. At 60% I saw the change.
My question is will the IC within the  lights respond correctly with these lower voltages during a sequence that requires them to do something other than just turn on?  Is there a minimum voltage for the IC?  Am I missing something else?



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Offline zwiller

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Re: WS2811 IC voltage drop tolerance
« Reply #1 on: January 20, 2017, 10:12:07 AM »
I'll pay along.  I don't think the F16 output adjustment should affect voltage per se.  It's not like a dimmer for incans where 50% reduction means 50% lower voltage.  I think it is software PWM but not sure.  So in the end, I don't think there as any issue where the IC will not have enough power.  That said, a single pair of 18awg for 300 pixels will no doubt cause some serious voltage drop and issues, yet alone 20' long.  18awg does not even appear on amperage distance charts...  Per the chart you'd need 12avg for that.  I realize you want to power these at 50%.  So if the relationship was linear (don't think it is) you'd need 14awg.  It is very wise that you are testing it.  Myself I would mount the board with it's own PS...           
Sam
 Last year's video: https://vimeo.com/150560653

Offline Emuney18

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Re: WS2811 IC voltage drop tolerance
« Reply #2 on: January 20, 2017, 06:04:28 PM »
So this years show I did both what you suggested. My setup was a PS with 1-2 receiver boards and I used 12 awg wire to run from that PS to a cg500 with a receiver board. I did this because I needed a smaller enclosure to fit just a receiver board. This year my plan was the smaller meanwell PS that MrSpoofy is offering with a single receiver board in a cg500.  This will actually be for 236 pixels. I was just testing to see if I could put the receiver in a TA200 and power it remotely.  These would be attached on the side of my house up high so my thought was keep PS tucked away somewhere.


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Offline zwiller

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Re: WS2811 IC voltage drop tolerance
« Reply #3 on: January 21, 2017, 06:42:02 AM »
Do you have some really long runs on the 2nd story?  With distance to first node being what it is, I simply can't see why anyone needs to do that but I was toying with the notion of sending power along side of data to a receiver as well and ran into the same issue.    Seems like no matter how hard I try I simple cannot break the port per prop/local PS thing...  You could still do the TA200 just feed it more than 18awg.  If you have some old SPT(16awg) test it.  I think you need to be well above 10V (like a 10% loss max) at end of string or white suffers.  You don't really notice this unless you have properly powered prop next to it.  If you do, it becomes obvious (pinkish).  Ohms law is not easy to get around but it can be done.  Best of luck. 

Offline arw01

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Re: WS2811 IC voltage drop tolerance
« Reply #4 on: January 21, 2017, 07:47:43 AM »
I put one power point on the roof this year, my general rule is NEVER put anything on the roof that is a point of failure for multiple things because it's not safe in my neck of the woods on the roof in the winter normally.

Other than a JST that required I go up on the roof it did fine, however this was feed with 18 gauge cable a good 40' and was more of a backfeed point to put more voltage in the roof outline of ws2811 10/30 strips.  For that it worked well.

I also had a Boscoyo Angel with it's 200+ nodes and I had real trouble with just 10' to the distribution and 15' to the angel with voltage drop.  I had to feed that one into the middle of the pixels and no back feed it, white would flicker out.

With a multi-meter I was seeing even at 10' and the angle 15' after that my voltage was leaving the supply at 12.6 and down in the 10's already at the distribution point. Up on the angle I was dropping below 5!

Plan to up the gauge of the wires this year, but I was using Ray's 2 wire pigtails and extensions for power injection, will require a new plan to use larger gauge over distance.


 

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