Using buck converters and RS485-TTL modules

I am still in the planning stages of my project to add permanent holiday lights at my house but I’m trying to work out some logistics. I wish to have my controller in one of my attic spaces (I have two insulated attic spaces) and will likely have to run power and data lines up to 100 feet from the controller to the start of a channel’s first LED. The LEDs that I am thinking of going with are WS2811 string lights at 12VDC. I am thinking of getting a 24V 1200 Watt power supply to power the LEDs and run 12 AWG wire from the power source fuse block to 24V->12V buck converters at the start and end of each channel of LEDs, and if needed at mid-span power injectors. My thought process in this design is to overcome line losses and ensure full 12VDC at each injection point.

I’m thinking that I will likely need to boost the data too but that would likely require converting the TTL signal to RS485 and back. These converters look to require between 3.3VDC and 5VDC. If this is the way to go, I’m guessing that I will need either a 5VDC power supply near my 24VDC supply or possibly just a 24VDC->5VDC buck converter near the 24VDC fuse block. For running the RS485 signals, I was thinking of running some CAT6A cable that I already have. Would I be able to run the RS485 signals over say the orange pair and run the 5VDC and ground over the green pair of the CAT6A to power the other converter? Should I double up on either the signal or power on the blue or brown pair?

You don’t mention what total LED count you’re anticipating?

1200W of PS should be able to take you up to 3500+ LEDs.

As far as the RS485 boards, you’ll want them at 5V for best compatibility.
A buck converter on the 24V line should work just fine.
Cat6A is suitable for the RS485 lines and can support the meager power they require as well.
Even at 100’ runs, the 5V supply for the RS485 boards is < 100mA so you can probably use a single 5V source without issue.

Your idea of using 12V converters is a good one, if you post a rough diagram of your layout and LED counts (and distances), we can give you some idea of the actual wire gauges you may be able to use.

Thanks for the reply. I am not exactly sure what my final LED count will be but I’m GUESSING that the linear feet will be around 400 feet. With pixels placed every 2 inches, that will be around 2400 LEDs. There are several segments that will be a pain to first measure and then finally install because they exceed any ladders I currently own. I’m trying to figure out if I can find a way to measure from the ground using some trigonometry. :nerd_face:

The reason I mentioned I’d use 12 AWG for power is that I already have a HUGE spool of 12 AWG DC zipline I purchased for another project; I also have a few boxes of CAT6A.

I have not yet purchased the 24VDC power supply but I was wanting to make sure I wasn’t taxing it if adding more. I am the type that likes to do a bunch of research before actually putting the knowledge to practice. I want to make sure that I have plenty of power where it is needed and make sure the lights are properly responsive. I am giving myself a time frame of 10 months to build this system.

You’re in good shape so far.

As far as measuring impossible things, I’ve actually had good success with Google Maps and their distance measuring tool. Won’t be perfect, but better than a ladder. Trigonometry can be more accurate, but it’s highly susceptible to errors in positioning on the ground. A laser distance tool and/or string lines can make this doable. The other thing I’ve done in the past is obtain actual drawings of the building construction and measure from that.

If you’ve got a surplus of 12AWG - have at it! I’d start looking for terminal blocks that will easily connect with 12AWG and let you down grade to 18AWG around the injection points. Much easier to do attachments with lighter gauge wire.

If you haven’t got the PS yet, you might think about splitting the project and use 2 supplies. That can reduce the longest run(s) of power lines. Even with good heavy gauge power, shorter is better.

Keep us posted, love to see new things go up (especially with pics)! :grinning: