distributed power

[bobschm]

Thinking about next year...

 

I'd like to learn more about distributed DC to my pixels. From auschristmas, I think it involves a huge power supply pumping 20-30 volts or thereabouts down the line. Then a DC convertor drops that to the 12 or 5 volts needed by each string.

 

So my question is what do I use for those convertors. I figure constant voltage and enough watts to run a string. But I'm looking for recommendations for manufacturers, sources, and such. There are a lot out there.

 

So many choices, so little knowledge.

[plasmadrive]

Lover your tag line  

 

"So many choices, so little knowledge. :unsure:"

 

I can tell you who I had the most trouble with.  prodc2dc.  Very high fail rate.  even 50% of the replacements failed before I even opened the package. (yeah, tested them thru the packaging while taking a video because they wouldn't admit they had a problem). Sent them the video and they stopped answering my emails. 

 

One even went high voltage on me and took out about 12 Plasma Icicles in one shot.  

 

I have left a few bad reviews and they refuse to post any bad reviews even though they were very factual...  Not someone I would do business with again.

[plasmadrive]

love.. not lover.. OMG.. LOL 

[aussiephil]

Hi Boston Bob,

 

Yes Constant Voltage is the go, as for wattage, you buy 5A - 10A - 20A versions based on the current draw of the strings you wish to power.

 

After 4 years of playing with distributed power i've learnt a couple lessons.

for 5V....

High concentrations of pixels that can all have short power runs (less than 8 feet) should have a dedicated 5V SMPS with a 100A rating

For more modular setup use 24V -> 5V DC DC convertors at each point with no more than 60% power draw of their rating as they tend to droop in voltage as current goes up.

here's a couple aliexpress links showing the two versions i have used over the last few years with few problems. You will always get some failures from the cheap construction, i've lost two out of twenty in four years.

http://www.aliexpress.com/store/product/20-PCS-LOT-DIY-Converter-DC-12-24V-to-5V-10A-Step-down-Converter-synchronous-rectification/215739_1572947535.html

http://www.aliexpress.com/item/Waterproof-Power-Adapter-DC-15V-55V-to-12V-3A-36W-Buck-Converter-for-LED-Driver-Car/1024976654.html

I haven't used this store, just an example of the product to look for.

 

For 12V.

I don't bother at all with DC/DC and just run semi decentralised AC-DC 12V SMPS - all 350W meanwell clones, as they are standardised they can be easily swapped in the event of failure.

All 12V cable runs are limited to 24 feet max and no more the 20% of the rated current of the cable to limit supply voltage drop. They 24 feet sets the radius for each SMPS placement.

[wbaker4]

This will help to understand voltage drop and how long runs at low voltages (like 5V) with high current (10-20A) is bad!

 

http://www.nooutage.com/vdrop.htm

 

Walt

[bobschm]

I bought 5v pixel strings and one thing I know now is that I should have bought the 12v versions. I think I can get these to run clean with a little more attention to power supply placement and some null pixels. (They ran a little pink, and when the snow and rain really came on, they started glitching.)

 

But I am considering a change to the roof line for next year, so there is where I want to run 24vdc and drop it to 12vdc at each 50 pixels or so.

 

Thanks. This info is very helpful.

 

Unlike the bacon thread, which wasn't much help at all.

[Ken Benedict]

Some of last years posts: http://forums.lightorama.com/index.php?/topic/27760-has-anyone-used-these-dc-dc-converters/

[plasmadrive]

Hey Bob,

 

I ran the Plasma Icicles from DC-DC converters, as I am sure you know by now.. if I can help with any of my garnered info, please ask. 

 

Craig

[bobschm]

In my case DC/DC makes sense. My power supply (probably 24vdc or more) will be in the garage so it doesn't have to be waterproof. I like the idea of a drop at each string so there will be no power issues.

 

And I'll even be able to drop voltage to the null pixels on long runs. I'm hoping this will eliminate the problems I saw this year.

 

Gonna need a lot of Ray Wu connectors.

[plasmadrive]

Well if you do decide you want weather proof supplies I have a bunch I put up for sale here.  I mounted mine under the eves but these are made for outside in the open.  Completely wet location rated.

 

http://forums.lightorama.com/index.php?/topic/30728-24vdc-waterproof-power-supplies/

[bobschm]

Still trying to figure out how much power I need. A pixel string is listed as 50 pieces of ws2811 pixels, like you're buying 50 items, instead of a single string. Then the power need is listed as 0.3w. So is that for the string, or an individual pixel?

[plasmadrive]

For the most part, 5v WS2811s run a bit over 1.5 amps per 30 pixels.  I was drawing about 3.3 amps at 5.0vcd with 60 pixels.  Keeping in mind that I injected power in between the 60 pixels so my Vdrop was quite minimal so my current draw was close to the max for those pixels.

 

So anyway.. 5V x .06A is .3W per pixel

[bobschm]

So conservatively a 24v 15 A supply for 200-250 pixels should be good? And the only real advantage to 12v over 5v pixels is I can get away with fewer injection points with 12v strings?