I have some questions before I place a RAY WU order

Re Power injection for the windows.... the strips effectively form a circle... just have power going to the start of the strip and the end of the strip which will be at the same physical point on the window
 
AussiePhil said:
Re Power injection for the windows.... the strips effectively form a circle... just have power going to the start of the strip and the end of the strip which will be at the same physical point on the window
Click to expand...


Some on mentioned to me since I am only using 3 of the 4 pins, running an extra positive on that 4th pin and running that instead of 2 wires I'm assuming I could run the 3 pins to the start of the "circle" and then the 4th pin which is the 2nd positive would run to the end of the "cirlce".
 
i13 said:
You are correct about the number of cores.

As far as I know those are not AWG sizes. The description of the cable I linked to says it is thicker than their 4 core cables. I thought the 24 part referred to the number of smaller strands within the cores. The 020 is the size of each strand.

The 101 manual is here
http://auschristmaslighting.com/forums/index.php/topic,1889.0.html
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I just tried to order it and it said I couldn't ship to my address (east coast USA)
 
I did not know that you live in the USA. I skimmed through your posts and couldn't see anything about that so I just said what I use.

It would be slightly better to connect the negative to both ends of the circle too. Doubling the positive will help reduce voltage drop but remember that it can occur in the negative line as well. Bench testing with the lead-in cable is a good idea. The data should only be connected to one end if the circle.

Your address might be an issue when trying to get a PixelBone too (ask smartalec). It wouldn't surprise me if there's something similar in the US though because Falcon Player (which is American) supports it. The guys at falconchristmas.com might know and many of them are ACL members too.
 
i13 said:
I did not know that you live in the USA. I skimmed through your posts and couldn't see anything about that so I just said what I use.

It would be slightly better to connect the negative to both ends of the circle too. Doubling the positive will help reduce voltage drop but remember that it can occur in the negative line as well. Bench testing with the lead-in cable is a good idea. The data should only be connected to one end if the circle.

Your address might be an issue when trying to get a PixelBone too (ask smartalec). It wouldn't surprise me if there's something similar in the US though because Falcon Player (which is American) supports it. The guys at falconchristmas.com might know and many of them are ACL members too.
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I found this wire http://www.ebay.com/itm/500FT-Security-Burglar-Alarm-18-4-Cable-Unshielded-Stranded-Speaker-Wire-White-/290919809508?hash=item43bc2c01e4 some one recommended it to me in the wire section on the forum.


You mentioned a second negative, but how would I run that? I only have one extra pin since I am running 3 pin pixels on 4 pin wire, so I only have room for 1 extra positive or one extra negative. How could I run both an extra of each? I can't find any decently priced 5 conductor 18AWG wire. Should I just go with one extra positive or forget about the extra +/- all together. someone mentioned I should be fine running one wire for 5 meters, my strips are going to be 5.8meters, so will the extra positive be fine if I don't use an extra negative?
 
It shouldn't really make a difference whether you double the positive or the negative instead. It is better than not doubling anything but not as good as doubling both. Even if you have just one negative wire, it is slightly better to branch the single wire to both ends of the strip so the current doesn't have to travel the entire length of the strip to get to an end that's not connected to the negative input. The set number of cores is the reason that I just buy the splittable figure-8 cable and run the wires together with cable ties.
Bench testing will confirm whether there's a voltage issue and voltage drop won't damage anything. I don't have the experience testing the limits of voltage drop for 5V lights first-hand. One thing that will have a big impact on the voltage drop is the distance the power needs to travel in the cable.

Hopefully someone with better 5V experience will post here. There are ways around the problem such as DC-DC converters with different voltage supplies if you want them too far away from the power supply using just cables.

Edit: AAH pointed out the difference.
 
i13 said:
It shouldn't really make a difference whether you double the positive or the negative instead. It is better than not doubling anything but not as good as doubling both. Even if you have just one negative wire, it is slightly better to branch the single wire to both ends of the strip so the current doesn't have to travel the entire length of the strip to get to an end that's not connected to the negative input. The set number of cores is the reason that I just buy the splittable figure-8 cable and run the wires together with cable ties.
Bench testing will confirm whether there's a voltage issue and voltage drop won't damage anything. I don't have the experience testing the limits of voltage drop for 5V lights first-hand. One thing that will have a big impact on the voltage drop is the distance the power needs to travel in the cable.

Hopefully someone with better 5V experience will post here. There are ways around the problem such as DC-DC converters with different voltage supplies if you want them too far away from the power supply using just cables.
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what percentage of voltage drop is generally bad? http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=20.95&voltage=5&phase=dc&noofconductor=4&distance=20&distanceunit=feet&amperes=7.2&x=68&y=15 I found this calculator.


Is it asking for the distance of pixels or distance of wire?
 
You're reaching the limit of what I know when asking about what percentage voltage drop is an issue.

The voltage drop calculator will only calculate the voltage drop in the cable itself and not what occurs within the pixel strips. You'll need to separately calculate the voltage drop for the single negative and doubled positive because doubling the wire is effectively changing its thickness. The calculator is taking into account the number of pixels (more pixels = more current) and the wire distance is the value it asks for.
 
A drop of about 10% is usually at about the limit of what the pixels will handle. That's the basis for the calculation formulas that are in the latest ACL 101. Any more than 10% and you will start getting pinkness occurring when white is displayed and eventually the pixels will stop responding at all and may latch up and require a power cycle to get them responding again.
Doubling up the 0V wire is better than the 5V/12V wire as the 0V has a bit more current flowing through it (5V or 12V return as well as data return) and as it's the reference for the data wire it needs to be as stable as possible.
 
Good point AAH; I didn't consider that. I apologise for the slight error in what I said. Doubling the negative is better than doubling the positive but still not as good as doubling both. It would be the single positive wire that you'd branch and connect to both ends of the strip.

AAH is 10% the voltage drop at the start or the far end of the strip?
 
i13 said:
Good point AAH; I didn't consider that. I apologise for the slight error in what I said. Doubling the negative is better than doubling the positive but still not as good as doubling both. It would be the single positive wire that you'd branch and connect to both ends of the strip.

AAH is 10% the voltage drop at the start or the far end of the strip?
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I guess I just don't understand why if its not supplying the power and if it is the other "end" why it needs to be doubled. I will do it that way as you say it is better, but I think that if I am going to proceed with this technique, that I should know the technical reason why I am doing so.
 
The negative is supplying power. Electricity is a flow of electrons from negative to positive but we usually work in terms of conventional current flowing the other way. I'm probably in a minority who actually think in terms of electron flow.

Keep in mind that it is the current that lights up the LEDs and a drop in voltage causes a drop in current.

Voltage drop should be minimised on the way to AND from the lights. The current is flowing through a complete circuit. The amount of current flowing is determined by two things; the supply voltage and the total resistance in the circuit. Look up Ohm's law for more info. It does not matter where the resistance is, it will still reduce the current that is able to flow through the complete loop including the LEDs. A single wire has more resistance than a doubled wire.

The reason I suggest connecting the single positive wire to both ends of the strip is similar. The current has to flow through a shorter path to/from what would have been the far end of the strip. There is resistance in the strip itself so you want to minimise the amount of current that needs to flow through the strip itself.

It took me a while to understand the technical reasons too but the key for me was understanding Ohm's law which is the relationship between current, voltage and resistance.
 
When you "consider" the 10% drop, you figure it from the output of the power supply to the end of the pixels. So it depends on the length of your power cables as well as the length of the pixels that you are powering. Ideally you want as little drop as possible in the wire feeding your strip or string. Then you figure your drop in the string or strip based on the specs for the pixels so that you can figure out where to do power injection if you need too.
As far as the size of wire for power, that depends on the voltage and current you need as well as the distance that you need to run it.
Seems complex but really is not that bad to do. The tables on here and other forums will make it easier. Also if you are using power supplies close to your pixels, it is less of a problem with the drop.
Some use more power supplies to compensate for distance or use higher voltage supplies and DC to DC down converters at each pixel string or strip (think 24 VDC supply and 5 VDC down converters at the pixels).

AAH was conveying that the negative lead not only carries the return on the positive power (ie 5V at X amps) but also the signal return of the data line back to the ground reference point. Hence you want your zero or negative line to be stable at zero so a slightly larger negative lead can help.

Using 5 V pixels is more touchy than 12 V since the lower voltage means less leeway for error or drift from the target 5V.
This is not an exact explanation but hope it helps somewhat.
 
Voltage drop and the 10% discussion.

Some real world voltage readings that throw the 10% number well and truly in question.

Baseline numbers
PSU 350w 5V nominal
PSU no load Vout : 5.55V
PSU load Vout: 5.54V

Cable from PSU to String input:
5M 32x020 10A figure8 cable

Pixel String 100 count 2811 nodes, single ended power feed for testing
Vin to string, No Load: 5.54
Vin to string, full white: 4.5V
current draw @ 2.6A at PSU
String starts to get pink ting around pixel 60.

2811 IC
Vin (min) 3.3v (-+0.7v)
Vin (max) 6v to 7v

Currently unmeasured
Voltage at middle of string
Voltage at end of string

Now some conclusions

Voltage drop on supply cable: 18%

typically a blue led requires 3.4v for Vf this gives a potential for 38% allowed drop from 5.55v before white is no longer white

The 2811 IC will function down to and potentially below 3.3v a 40% drop from 5.55v

It is ABSOLUTELY critical that the input voltage is held as close to 5v at the start of the string to minimise voltage drop issues.

No load voltage should ever be much high than 5.6v at the PSU

Even shortish runs of cable will have voltage drops that can affect things at 5v
 
AussiePhil said:
Voltage drop and the 10% discussion.

Some real world voltage readings that throw the 10% number well and truly in question.

Baseline numbers
PSU 350w 5V nominal
PSU no load Vout : 5.55V
PSU load Vout: 5.54V

Cable from PSU to String input:
5M 32x020 10A figure8 cable

Pixel String 100 count 2811 nodes, single ended power feed for testing
Vin to string, No Load: 5.54
Vin to string, full white: 4.5V
current draw @ 2.6A at PSU
String starts to get pink ting around pixel 60.

2811 IC
Vin (min) 3.3v (-+0.7v)
Vin (max) 6v to 7v

Currently unmeasured
Voltage at middle of string
Voltage at end of string
Click to expand...


Ok to add to the information 100count


Voltage middle full white - 3.4V
Voltage end full white - 2.35V


Interestingly the end string voltage for full single colour was 3.38V.


Next test, reduce the overall brightness to 50%
Full white end voltage went up to 3.14V
 
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