My first DIY Pixel Experience

[Crazydave]

so i purchased an e681 from sandevices and I ordered some 12v ws2801 pixel strings (100ct per string) and 4-condutor water proof connectors from Ray Wu, along with a couple Meanwell NES-100-12 and a couple of CG-1500 cases from WLC Ventures

Lessons learned:

1.) The strings were not in stock.. and it took 3 weeks to have them made. Ray initially told me it would only take a week.

2.) The stings I got were correct and did work flawlessly out of the box... however it was not factory perfect. some of the pixels were soldered in (either in the middle or at the end)

3.) Double and triple check the wire before connecting! The color coding on the pixel strings seem a bit odd to me: (and was different from the pictures)

Black : +12v (yes black was the +12v)

Red: clock

Green: data

Blue: power ground

I therefore had to look very closely through the opaque pixels with a magnifying glass to figure out which wire was which. (the black +12v was the most suprising... and this kept screwing me up later when I was wiring these strings to the connectors i sacrificed 2 pixels because I swapped the + and (-) )

4.) Using the 12v pixels... I was able to create a single string of 158 pixels. It did not require any power injection to work properly. There was no color fading at the far end. I even had a 30 foot leader with 3 null pixels (using spt-2). However when I inserted power at pixel 79, the entire string got a little bit brighter. (I'm, thinking 12v is the way to go)

(I'm not sure how far the ws2801 pixels will travel before requiring a null pixel so I just put one every 10 feet, I will update that when I make my next string)

[Guest wbottomley]

Great information.

Thanks Dave.

[vincerules]

Thanks for the write up, I'm currently waiting for my strips from Ray to arrive.

[edvas69]

Glad it has worked well for you Dave, now you have that ever lasting hunger for more pixels.

The differences between using 12vdc and 5vdc pixel strings both have advantages and disadvantages

12VDC allows longer strings due to less % of voltage drop over the same distance as 5vdc

12VDC will use and waste a lot more power than 5vdc which means providing more power supplies

Some 12vdc strings like the 180x series run in constant voltage mode as apposed to constant current mode. LEDs are a current devices so constant current is a better method of control. Im not sure if the 12VDC 2801 has been set to run in constant current or constant voltage mode.

12VDC will dissapate a lot more heat than 5vdc due to the wasted energy.

5VDC requires more power injection due to both the higher currents and higher % of voltage loss over the same distnace as 12VDC

5VDC requires larger guage wire compared to 12VDC for the same power requirements.

5VDC is much more efficient than 12VDC and requires less power supplies for the same amount of light output.

To see this we will compare a 12VDC and 5VDC string using 8mm LED

8mm RGB LED Specifications

Red - 20millamps - 2 volts

Green - 20 milliamps - 3.2 volts

Blue - 20 milliamps - 3.1 volts

So to run the red LED we need to drop the voltage from 12VDC to 2VDC, as you can see there is a much higher % of volts that need to be lost to run at 12VDC compared to that of 5VDC. So there is a lot of wasted energy. One way that is used to to minimise the amount of lost energy through a 12VDC string is to run the LEDs at a lower current, so instead of running the LED at the rated 20ma for each colour, they will instead be set to run at 10ma (these values may differ), this then reduces the amount of wasted energy due to the lower current needs of the LEDs. But as LEDs are current devices, the lower current will reduce the light output. Now normally at 10ma the human eye cant really notice a great difference when looking at the LED compared to being run at 20ma, but what happens is the effective light output is reduced and this will show with a light meter, this will then reduce light wash and surrounding light generated by the LED.

The reason why we see 12VDC strip and modules is because they have 3 LEDs connected in series, so the red LED circuit would then be 6vdc (3x2v), this makes much better use of 12VDC than using a single LED.

5VDC is used for single LEDs and 12VDC is used for multiple (3) leds. 12VDC string were designed to help overcome the voltage drop and current needs of using 5VDC strings.

So now knowing the differences and the advanatges and disadvantages should help people decide if they prefer to use 5vdc or 12vdc strings. Personally i use a lot of strip and modules because it is 12VDC and makes efficient use of the power used compared to running 12vdc strings. The little strings I do have are 5VDC because that is the correct and most efficient design for using single LEDs

So really it goes down to

12VDC = Longer string length, more power used, low efficiency

5VDC = Shorter string length, less power used, high efficiency

Edited August 20, 2012 by edvas69

[Crazydave]

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Update

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12v ws2801 pixels using a 30' leader constructed of SPT2 wires does NOT require any NULL Pixels.

12VDC will dissapate a lot more heat than 5vdc due to the wasted energy.

I can feel that these pixels run warm

5VDC requires more power injection due to both the higher currents and higher % of voltage loss over the same distnace as 12VDC

I got 12v because I know I was going to have to make a long run to the eves, and then the eves would also be long runs.

[edvas69]

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Update

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12v ws2801 pixels using a 30' leader constructed of SPT2 wires does NOT require any NULL Pixels.

I can feel that these pixels run warm

I got 12v because I know I was going to have to make a long run to the eves, and then the eves would also be long runs.

Running warm may actually be a good thing for you guys up in the northern parts of the US, this will help melt the snow/ice away from the LEDs.

But for us in Australia, we want to avoid any exrta heat and wasted energy due to the excessive cost of electricity and the fact that our ambient temps in summer can be up to 30Deg C at night.

[Crazydave]

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Further Update

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I was incorrect about

12v ws2801 pixels using a 30' leader constructed of SPT2 wires does NOT require any NULL Pixels.

The 30' section was TOO long for the pixels to work properly. They would light up and change, however, they would not properly receive the 'OFF' command, so sometime they would turn on to whatever color your assigned, and then they would stay that color, even though the software said to go dark.

I inserted one (1) Null pixel at the 15' mark, and the string now performs flawlessly.

Also where I live it's doesn't snow.. so the extra heat is just wasted. The advantage is definitely in having long runs. I have pixel strings that are 100 pixels, 138 pixels, and 152 pixels long (all have 10cm spacing). Each with 20 or 30' headers. While I did have power injection on the 2 longer strings, I only needed one power injection on each. And even that power injection wasn't necessary.. as the colors were NOT shifting (from white to pink) . When I connected the power injection, the entire string got brighter, which I figured was better, so I did it.

Edited September 4, 2012 by Crazydave