How would you guys wire up RGB pixels that are anywhere between 3 to 20 feet apart? Think of wires hanging from the ceiling with a pixel hanging off of each one. It gets difficult wiring them all in series because you’d have to take the data lines down the wire to the pixel, then back up, then down again to the next pixel, then up again, etc., etc. So really if you have two pixels that are hanging 6 feet down, your data line will travel from the top->down->top->down->top again, or 24 feet (12 feet between pixels). If you have a bunch of them hanging, that becomes a rather long line to transmit down. Would it make more sense to have each pixel wired to say a tiny and have the tinys then wired together?
I had this problem with my Christmas display. I did something similar to the tiny suggestion but without wires, I made small arduino clones and used the nrf24l01+ RF transceivers to avoid the data wires. In cases where I had too many pixels and needed power injection I put the controller in the middle of the string and ran half of it backwards.
LED voltage and current? Wire gauge for power? Twisted pair (Ethernet) cable available for the signal. Do you have to buy the cables or are you reusing existing stuff? What about wiring to multiple pins on a single controller?
Yeah, the nRF modules came to mind but for this potential project it’ll be cost prohibitive. @Michael_Sharnet I’m not too concerned about voltage/current as it’ll be fairly easy to drive each pixel by themselves, it’s the data signal that’s I’m trying to wrap my brain around. And, it would have to be fairly thin wires to make it work (which again, I think I can accomplish, however running them in series is where the problem sits.) That’s why I thought of having each driven separately.
Wiring individual pixels on separate pins could potentially work as well.
I think you can get the signal to work by using twisted pair cables (Ethernet). Make sure to wire up the ground and the signal.
the modules are less than 1$ (cheaper than wire : ) ) … that said are you going to use strips or strings of pixels? If you use pixel Strips with the silicon tube you can always solder a small wire on the data pad at the end of the strip and run it back up the tube behind the pixels to make things nice and neat.
Nope, think of an xmas ball ornament hanging on a thin wire with a single RGB pixel inside … multiplied by 100 or more. Either each one gets wired separately to different pins on a large controller (which seems the more logical way to go) or I find a way to wire them in series … though I suspect that’s just way too much of a headache.
Each pixel would more than likely be a one-wire pixel to cut down on the wire thickness that I’d need to run down for each one (3-cores flat cable versus 4-cores, or if in series, it’s 4 or 5-cores.) Aesthetically, the fewer cores means a thinner cable.
Quite a challenge. and a lot of wires! I would think you could do the cat5 route using 3 pair for pwr and gnd and putting the data on the 4th. Kinda like the holiday coro wiring guide: http://www.holidaycoro.com/kb_results.asp?ID=92
If use cat5. Cheap to buy, simple to lay, and you could ease the process with standard connections and then a custom board.
Yeah but the three wires are still going to be too thick for my liking, however I may not have a choice. I need to get voltage/current down the line to the physical pixel.
I am trying to create a pattern of twinkle lights outside and I am curious how you are hanging the lights. Are the lights supported using only the wiring?
Uh, I haven’t done this project yet, so I don’t know how I’m going to do it yet. And it would be indoors. Originally I was thinking of hanging each ornament from a fishing line and run the wires along that. But, considering the weight and strength of the wires themselves, I may forgo the fishing line. For outside though, I’d suggest something other than just the wires, or use heavier gauge …
I would go for it with just the Ethernet cable perhaps add a loop near the end of the cable and tie a safety line to the actual ornament? Just watching out for the slam dunk wannabes that will try to “touch” anything in reach.
Oh I know … there’s a 4-legged and 2-legged one that would not hesitate at that opportunity … Thinking I may need to add a shock fence around the display. grin
I was thinking back to an escalator ride where the smart guy in front of me jumped up and “touched the ceiling” and ended up covered in plaster dust and crumbs. I guess he didn’t see or care that there was plastic wrap covering construction above.
Ashley,
I’m not sure what you do and don’t want to do with the data. Are you saying you OK with running data from drop point to drop point, but not happy with running it down and up to each of your pixels?
If you are happy running the data from drop to drop, then you could put your driver chip at the top and run 4 very fine wires down to your LED pixel. Assuming it is just the LED, then it is unlikely the you can find a RGB LED heavy enough to break the wires, even if they are couple of meters long. You would be limited to only a short distance between each driver chip at the top, due to signal degradation and capacitance of the cables.
Staying with that premise of the driver at the top, you could use a ATTiny at the top of each drop, with an accurate oscillator and create your own method of linking together. This rather precludes the use of FastSPI, unless you emulate a standard LED strip protocol.
Or you use an LED Pixel with an accepted driver chip to do your single pixel at the bottom of the drop. This would save 1 wire in the drop - not much of a saving. Personally I would put the intelligence at the top and use 4 wires in the drop (R,G,B & 0v) and hide the wiring to the LED inside a small diffuser sphere (e.g. Ping-Pong ball). There are some pretty small 4core cables around and it only needs to carry about 60mA after all for 1 RGB LED. You could even twist together Kynar which is around 0.6mm as an insulated diameter of single core. I have rolls of 4core I acquired many years ago that is only 1mm in diameter.
The intelligence at the top will also work for those ‘drip’ type effects you see around. These use DMX to inter-link the drips. With channels allocated for density, rate and colour.
Helpful?
Yeah I was thinking of that too. Drivers at the top, linked together for FastSPI, with four wires down to each LED. Meh, will need to sit on this on a bit longer.