Author Topic: Powering pixels thru the Cap  (Read 3640 times)

Offline SlammedNiss

  • Newbie
  • *
  • Join Date: Jan 2017
  • Location:
  • Posts: 29
  • Kudos: 0
Powering pixels thru the Cap
« on: January 29, 2017, 02:26:00 PM »
I can't seem to find a definite answer on this and maybe I'm just not asking the right question.

Can you power the pixels thru the PiCap or does it require external power injection?
People's misconceptions on adjustable suspensions usually come from a lack of knowledge.

Offline AAH

  • Hero Member
  • *****
  • Join Date: Jul 2014
  • Location: Australia
  • Posts: 740
  • Kudos: 19
  • Blinky blinky blinky
    • I love blinky lights
Re: Powering pixels thru the Cap
« Reply #1 on: January 29, 2017, 02:33:39 PM »
The Pi-Cap is likely limited to 7.5A on the pixel outputs which limits the number of directly powered pixels to about 135 at full brightness. To connect any more power injection would be required.

Offline SlammedNiss

  • Newbie
  • *
  • Join Date: Jan 2017
  • Location:
  • Posts: 29
  • Kudos: 0
Re: Powering pixels thru the Cap
« Reply #2 on: January 29, 2017, 04:41:58 PM »
I seem to be getting mixed answers. The post below (found in another thread) says "1000 per output on the PiCap". Or is he just referring to data?

The PiCap has several different uses.


In my case, I use it to take data from the FPP and send it out to a DMX data string. 
Others are using it where they only have a small number of pixels to drive.  I believe the count is up to 2000 (1000 per output on the PiCap).  That is enough to drive many different stand-a-lone props.

Even the official page states "Can control two strings 800+", but again I don't know if that's just data. I'm only looking to control about 500-600 pixels so don't know if I would need additional hardware.

Anyways, is the PiCap even available for purchase any where? It's OOS on the website.

 
« Last Edit: January 29, 2017, 04:55:44 PM by SlammedNiss »

Offline rlemery

  • Sr. Member
  • ****
  • Join Date: Feb 2015
  • Location: Morganton,NC
  • Posts: 370
  • Kudos: 5
Re: Powering pixels thru the Cap
« Reply #3 on: January 29, 2017, 04:55:02 PM »
You need power injection for more than 135 pixels or so less if using 5v.. This is normal no matter what controller is used. The Pi will run between 800 and 1000 per output. As far as availability there should be a pre-sale coming any time on www.Pixelcontrollers.com .
rons holiday lights has picap boards for sale on renard-shop.com but these require ordering the parts from digikey and lots of soldering. I have used Ron's boards and they work great. Just takes time to assemble.

Sent from my SM-G920V using Tapatalk

728 lor channels
5492 pixels

Offline deplanche

  • Full Member
  • ***
  • Join Date: Aug 2015
  • Location:
  • Posts: 234
  • Kudos: 5
Re: Powering pixels thru the Cap
« Reply #4 on: January 29, 2017, 06:13:43 PM »
I can't seem to find a definite answer on this and maybe I'm just not asking the right question.

Can you power the pixels thru the PiCap or does it require external power injection?

If you are asking if you can run the pixels off the power you are supplying to the Pi, then No, you can't do that.  You power the pixels from power that goes into the picap.

If you have more than ~125 pixels, then you'll need power injection.  That number varies depending on pixels type, spacing, etc.

Offline SlammedNiss

  • Newbie
  • *
  • Join Date: Jan 2017
  • Location:
  • Posts: 29
  • Kudos: 0
Re: Powering pixels thru the Cap
« Reply #5 on: January 29, 2017, 06:39:32 PM »
If you are asking if you can run the pixels off the power you are supplying to the Pi, then No, you can't do that.  You power the pixels from power that goes into the picap.

If you have more than ~125 pixels, then you'll need power injection.  That number varies depending on pixels type, spacing, etc.

No, there would be an external 350W PSU that I would be using.

Offline algerdes

  • Supporting Member
  • ******
  • Join Date: Apr 2014
  • Location: Lebanon, Illinois
  • Posts: 914
  • Kudos: 13
Re: Powering pixels thru the Cap
« Reply #6 on: January 30, 2017, 12:18:16 PM »
I seem to be getting mixed answers. The post below (found in another thread) says "1000 per output on the PiCap". Or is he just referring to data?

Even the official page states "Can control two strings 800+", but again I don't know if that's just data. I'm only looking to control about 500-600 pixels so don't know if I would need additional hardware.

Anyways, is the PiCap even available for purchase any where? It's OOS on the website.


The website is stating what was the number of pixels when it was first created.  The "1000 per output..." line was from threads here and on the other DIYC sites stating that they had squeezed more from the code. 

The best answers will come from the creator of the PiCap - David Pitts, and the primary developer of the Falcon Pi Player - Chris Pinkham (Captain Murdoch).

And yes - the "control" mentioned is the data capability.  The number of pixels you can power *directly from the PiCap* is no where near the number of control channels it can address.  Power "injection" is a must once you reach the standard number for the voltage and wire sizes of the pixels you are using are met.

Additional - One thing that the PiCap has on it that is really nice is the ability to power the Raspberry Pi from the PiCap - no power needed directly feeding the RPi's power input.  If you are feeding 12v or 5v to the outputs on the PiCap, the RPi can get its power from the header.  See the instructions for the PiCap for how to make this happen.
« Last Edit: January 30, 2017, 12:48:50 PM by algerdes »
Sequencers: Vixen3 and xLights
Players: FPP and xSchedule Controllers:  Renards - SS24/SS16; E1.31 - San Devices E682 - Falcon F16, F4, F48 - J1Sys - DIYLEDExpress E1.31 Bridges.  Much more!

Offline gilv58

  • Jr. Member
  • **
  • Join Date: Jan 2017
  • Location: Helotes, TX
  • Posts: 52
  • Kudos: 0
Re: Powering pixels thru the Cap
« Reply #7 on: January 30, 2017, 01:30:03 PM »
Additional - One thing that the PiCap has on it that is really nice is the ability to power the Raspberry Pi from the PiCap - no power needed directly feeding the RPi's power input.  If you are feeding 12v or 5v to the outputs on the PiCap, the RPi can get its power from the header.  See the instructions for the PiCap for how to make this happen.


Yes this is  very nice feature I "discovered" by accident. I was running a sequence as part of my test and though I would turn it off my powering down the wall wart that directly powers the Pi but left the PS connected to the PiCap. After a while, much to my surprise, the sequence continued to run. Of course a closer inspection detected the lights on the Pi were still on.


A nice feature indeed.


Gil V.
Gil V.

Offline gilv58

  • Jr. Member
  • **
  • Join Date: Jan 2017
  • Location: Helotes, TX
  • Posts: 52
  • Kudos: 0
Re: Powering pixels thru the Cap
« Reply #8 on: January 30, 2017, 01:38:15 PM »
I can't seem to find a definite answer on this and maybe I'm just not asking the right question.

Can you power the pixels thru the PiCap or does it require external power injection?


I am no expert and just learning myself but I think of the Pi (when its by itself) as a micro computer you can use to control/drive pixel controllers. You need to connect a Pi to some controller (F16Vx, PiCap, E682, LOR, etc etc) to actually control or drive the pixels. These controllers will have a power input that usually powers both the controller and the pixels they are driving.


Gil V.




Offline SlammedNiss

  • Newbie
  • *
  • Join Date: Jan 2017
  • Location:
  • Posts: 29
  • Kudos: 0
Re: Powering pixels thru the Cap
« Reply #9 on: January 30, 2017, 10:22:27 PM »
I am no expert and just learning myself but I think of the Pi (when its by itself) as a micro computer you can use to control/drive pixel controllers. You need to connect a Pi to some controller (F16Vx, PiCap, E682, LOR, etc etc) to actually control or drive the pixels. These controllers will have a power input that usually powers both the controller and the pixels they are driving.


Gil V.
Thanks, but my question was regarding the amount of pixels a PiCap would run before needing power injection. From the answers given already, it's about 125 or so before needing to inject power.

Offline algerdes

  • Supporting Member
  • ******
  • Join Date: Apr 2014
  • Location: Lebanon, Illinois
  • Posts: 914
  • Kudos: 13
Re: Powering pixels thru the Cap
« Reply #10 on: February 02, 2017, 01:58:24 PM »
Thanks, but my question was regarding the amount of pixels a PiCap would run before needing power injection. From the answers given already, it's about 125 or so before needing to inject power.


The number of pixels you can drive directly from the RPi/FPP and the PiCap depends on the voltage and type of pixel.  The "rule of thumb" varies. 


For 12v pixels, you can usually get between 100 and 125.  Most will state you need to add power injection at the 100 point.


For 5v pixels, according to those that use them, you can usually get between 50 and 65.  Here again, most will tell you to power inject at 50.


All of my pixels are 12v.  I have had experiences at both ends of those scales.  I've had 12v pixels that I could drive 130 without problem, then a like set of 12v pixels that I had to inject just after 80.  With this said, the 100 for 12v rule seems to be a good guide.


You need to try your own in the situation you want them.

Offline Ray

  • Newbie
  • *
  • Join Date: Feb 2015
  • Location:
  • Posts: 34
  • Kudos: 0
Re: Powering pixels thru the Cap
« Reply #11 on: February 10, 2017, 04:29:26 PM »
Hmm, just got my cap and noted that both of the green LED connectors are fused for 5A each. Now if I have this correct, most WS2811 pixels draw 60mA when producing a white light (all 3, R,G,B LED are on). I dont like to take things to 100% loading, so I used a 4.5A divided by .06A to get a total of 75 pixels per connector. So, after 75 pixels I am going to inject. I am having problems with figuring out where I am erroring with my numbers? Would someone point out my mistake.

Offline Bwinter

  • Sr. Member
  • ****
  • Join Date: Jul 2016
  • Location:
  • Posts: 435
  • Kudos: 10
    • First Show 2016
Re: Powering pixels thru the Cap
« Reply #12 on: February 10, 2017, 04:53:44 PM »
Hmm, just got my cap and noted that both of the green LED connectors are fused for 5A each. Now if I have this correct, most WS2811 pixels draw 60mA when producing a white light (all 3, R,G,B LED are on). I dont like to take things to 100% loading, so I used a 4.5A divided by .06A to get a total of 75 pixels per connector. So, after 75 pixels I am going to inject. I am having problems with figuring out where I am erroring with my numbers? Would someone point out my mistake.

I assume you're using 5V.  12V uses 45mA/node.

I think your numbers are correct.

Offline bpos

  • Full Member
  • ***
  • Join Date: Mar 2015
  • Location:
  • Posts: 132
  • Kudos: 2
Re: Powering pixels thru the Cap
« Reply #13 on: February 10, 2017, 11:10:14 PM »
Hmm, just got my cap and noted that both of the green LED connectors are fused for 5A each. Now if I have this correct, most WS2811 pixels draw 60mA when producing a white light (all 3, R,G,B LED are on). I dont like to take things to 100% loading, so I used a 4.5A divided by .06A to get a total of 75 pixels per connector. So, after 75 pixels I am going to inject. I am having problems with figuring out where I am erroring with my numbers? Would someone point out my mistake.

Theoretically its probably more like .33 per pixel @100%. Your not going to pull 100% from all of the pixels at once very often if at all. And even if you do it wont be for more than a few seconds. I run 300 pixels on one line and inject every 100 and there are no issues at all. Once the injection hits the draw is about 1/3rd of what it would be if it ran one direction to the end. Its up to the size of power supply to keep up with draw demand.
 Another way to look at this is you are drawing amperage from the first 100 pixels (in this example) and just data after that. Seems to me that the first injection point would bypass the fuse after that (except for data)?
So figure about drawing .13 on average with power injection cutting that consumption down drastically would give you somewhere in the neighborhood of 700 pixels with ease?

Just some hypothetical number ideas..
« Last Edit: March 02, 2017, 04:55:50 PM by bpos »

Offline Ray

  • Newbie
  • *
  • Join Date: Feb 2015
  • Location:
  • Posts: 34
  • Kudos: 0
Re: Powering pixels thru the Cap
« Reply #14 on: March 01, 2017, 07:50:11 PM »
Ok just for the sake of discussion. I have converted many ican display items over to using LED lamps. All of these LEDs consume 20mA at full on. So with 3 LEDs in each pixel with all 3 turned on full should draw 60mA per pixel. So, from MY past experience I am not real sure were every one is getting these lower figures?  True most often not all pixels are programmed to be white and at 100%. But if you plan on it, then you wont have to worry about any problems.

BTW to my knowledge the only difference between the 5V and 12V pixels is the 12V pixels use resistors to limit the current to 20mA thus dropping the voltage across the LEDs and the WS2811 chip. Current draw should be the same overall. Now I will say that this is book knowledge, I do not own any 5V pixels that I would be able to test myself.
 
Ray

 

Back to top