1
\$\begingroup\$

I'm trying to build a LED panel around my living room, using 10 strips of ~10m packed with WS2812. A rough estimation of the power required with all LEDs at full brightness would be 700 W.

The flexible PCB of the LED strips of course cannot carry that amount of power, so I need to feed power at least once every meter. I'm looking for the sanest way to do that.

My current approach would be two metal pipes along the wall (that would also provide the support), and having individual panels clip onto those, and simple connectors for the signal lines. I'd directly distribute the 5V from the PSUs.

Questions:

  • is this a good approach, or is there a better way?
  • if I have two PSUs, each for 350W max, does it make sense to connect one to each end of the rail?
  • if I assume that most of the time, I'll have a load of ~20W (because brain surgery is my hobby, not my job), is there a way I could make this more efficient?
  • if I assume that I won't ever need all LEDs on at the same time, can I somehow enforce this (e.g. use three rails, if rail 1 uses more than 175W, power down rail 2 so the entire power consumption will not exceed 350W)?
\$\endgroup\$
9
  • \$\begingroup\$ can't you go up in voltage with your power system? That's a lot of A going around... \$\endgroup\$ May 12 '14 at 9:22
  • \$\begingroup\$ I can, but then I need to step down. If I use 12->5V converters with 1A output, I'd have to buy and solder an entire reel of them. \$\endgroup\$ May 12 '14 at 10:17
  • \$\begingroup\$ just wire the strips in series, that's the point of going up in voltage. \$\endgroup\$ May 12 '14 at 10:26
  • \$\begingroup\$ That would only work if the strips used the same amount of power each, which isn't given. \$\endgroup\$ May 12 '14 at 10:39
  • \$\begingroup\$ Have you considered the heat output of this LED array? \$\endgroup\$
    – Emyr
    May 12 '14 at 10:44
1
\$\begingroup\$

750W of LEDs is a lot. You'd probably need a welding mask to do anything in that room. Bear that in mind - perhaps consider setting the software to never get anywhere near maximum brightness.

It's not a good idea to connect 2 power supplies in parallel to the same rail. The voltages they output won't be exactly the same and, depending on the exact topology of the power supplies, unwanted and potentially damaging things could happen.

I assume that you're proposing using the pipe as the main conductor, much like the cable track lighting shown on that page? You should break the pipe and provide an independent piece of pipe for each power supply you have. The 0V can (and should) be in common.

Monitoring of the power use could be done in a number of ways. The simplest would be a fuse or circuit breaker. It would also be the crudest method. Current monitoring is typically done using a current shunt monitor - essentially a low value resistor and a method of monitoring the voltage drop over it. As the current increases, the voltage drop increases until it's above a threshold, at which point something is done. You can get ICs which do most of it for you, or you can build a current limiting circuit with not much more than an opamp, a handful of resistors and a mosfet. I assume you're actually controlling the LEDs with a microcontroller or similar? An alternative option would be to feed the output of a current monitor into the microcontroller and to take action when the value is over a specified amount - perhaps by uniformly dimming the LEDs.

Without knowing your specific application it's hard to make recommendations. If you can reduce your requirement to a few hundred watts (which is still a huge amount of light to have indoors) then life will be a lot easier. Remember that just because an LED strip can consume a certain amount of power at full brightness doesn't mean you have to command it to.

\$\endgroup\$
3
  • \$\begingroup\$ Yes, using the pipe as the main conductor is the plan. Splitting it in half and feeding from both ends sounds like a good idea then. \$\endgroup\$ May 12 '14 at 10:40
  • \$\begingroup\$ Indeed, the requirement is a lot less than full output power, but as I'm experimenting with the software, I'd like for the system to be able to handle programming errors that activate all LEDs. The easiest way to break these LEDs is to ever have the voltage on the data input (which comes from a RasPi) exceed the supply voltage by more than 0.3V. \$\endgroup\$ May 12 '14 at 10:42
  • \$\begingroup\$ Actually, paralleling two power supplies is not, in general, a terrible idea. Assuming that each supply transitions gracefully from constant voltage to constant current, whichever has the higher voltage will supply all the current up to its current limit, whereupon the other will start supplementing as necessary. This approach is worthless if the supplies use foldback limiting, but that seems to be rare these days. \$\endgroup\$ May 12 '14 at 12:35
0
\$\begingroup\$

Wonderful project. Here is something that would really help from my project.

  1. If you use open metal pipes to supply power, you actually waiting for disaster to happen. At some point, something will touch those two pipes and 70A current will destroy your work.
  2. You must use an appropriate gauge copper core (Single core) cable from the power supply to a connector similar to this. You can use 2 connectors separate for 5V and GND. Then connect the strips to connector.
  3. You must carefully choose the gauge of the wires so that current won't heat your wires.

This is how I implemented my design. I  know my drawing is worst. If it helps you my efforts were worth it.

You are using two power supplies, so you must connect ground pin of both connector together.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.