Christmas light pixels can be really fun, but one of the most intimidating aspects of using them is power.
While “regular” Christmas lights run a full, high voltage from your standard wall outlets, pixels are a low-voltage product.
They don’t use a lot of power, but they are picky about the characteristics of that power. When we’re working with low voltage, our primary issue is from voltage drop.
What is Voltage Drop?
Voltage drop truly is as simple as it sounds. Because we are working with a low voltage, generally 12v or 5v, at a certain point (about a 20% drop) the voltage gets too low for the pixels to operate properly.
This is a phenomenon that happens with all electricity. As electricity goes through wires over distance, it loses voltage. Because regular Christmas lights run at line voltage (115v here in the US for homes), a drop of a few volts over the length of wire doesn’t generally cause any problems – it’s a small percentage of the total voltage.
But when a few volts drop at 12v, it is too low for the pixels to work properly. So, we need fresh power!
One of the cool things about pixels is that they can be powered via a variety of different ways. The power for your pixels can come from the start of the line of pixels, from the end, or even the middle! The power also can come through the controller, or bypass the controller entirely.
This can make power both simple, but also confusing, especially when you are first getting started with pixels.
There are a few main ways that you can add power to your pixels, starting with…
From The Controller
Many pixel controllers are designed to provide some power to the pixels. After all, the controller needs power, and the pixels need power, so it just makes sense to add it here.
Most controllers also have fuses on board to protect both the controller and the power supply from any electrical issues that may come about – primarily loose connections which heat up or failures of cheap power supplies.
When you’re working with 12v pixels, you’ll find that you can run anywhere from 100-300+ pixels straight from the controller before you need more power. The total number depends on the wattage of your pixels, the size of wire and distance, your power supply’s actual voltage, and what percent you run the pixels at in your show.
Generally, when the voltage gets down around 11.6v, it’s time to re-inject power!
Remember, voltage is going to drop over the distance of wire, so extensions that you use from the controller to your pixels will contribute to voltage drop.
Thicker extensions offer less voltage drop, but the more power you have connected at the end of an extension, the more drop you will see.
You can test this yourself with your pixels to see what your drop looks like in “real life”. And remember, it’s better to stay on the safe side, rather then max out every power supply and run into issues if your voltage drops a hair!
Providing power from the controller can work well, but I generally don’t recommend it, especially on larger controllers.
As you begin to add more and more power through your controller, you increase the risk of the power input on that controller electrically arc-ing – and this can destroy your controller!
No, this shouldn’t happen, but connections get loose over time, and it does happen to folks. Even if the connections are good, cheaper power supplies can fail in a very dangerous way and take out other components as they die.
With a simple difference in wiring (but mostly the same components), we can get the same power to the same pixels, without running through our controller.
This protects the “brains” of our operation and doesn’t require much more in gear, so it’s a “win” in my book!
From a Power Supply
12v power supplies can be used to add in power separately from the controller as well.
This can be done for the purposes of power injection (see below), or as a safety measure to keep less power running through the controller.
It’s really as simple as wiring your pixels from your controller with the DATA wire and the GROUND (-) wire, and then running from the power supply with the Ground (-) wire and the +5v or +12v wire to your pixels. You will want to provide a fuse between your power supply and your pixels as a safeguard against any arc-ing or a power supply failure.
This provides the power separate from the data and keeps the amount of power running through your controller minimal.
As a bonus, you can locate the power supply much closer to the actual pixels if desired, and cut down on the voltage drop. This allows you to run more pixels before re-injecting power.
As I mentioned above, using fuses is important to protect your power supplies and controller boards. Just like your home as circuit breakers, fuses protect your hardware when pixels unexpectedly draw more power than they are supposed to.
This can happen when there is a short in the electrical cable or a loose connection causing arcing. Or, it could be that you just hooked up way too much to one run of power, though with pixels you usually see the effects of voltage drop way before this!
Some folks use automotive-style fuse blocks like this, but I prefer using distro boards designed by the Christmas light community.
The Christmas light style distro boards are much quicker and easier to use with your controllers, and the fuse sizes supplied are generally matched to what we need. Plus, they don’t really cost any more, so you can’t go wrong there!
The 1000-pound bear to tackle here is this: power injection.
As we’ve mentioned before, there will come a point in your pixel strings that your voltage drops too low, and you need to re-inject power. Because there are a lot of options on how to do this, it can get confusing – but it doesn’t have to be confusing.
Like anything in your display, I recommend choosing one method of power injection and then stick with it for all of your power injection within your display. This allows you to more quickly and easily change out components and test for problems later in the process.
At the base level, power injection is no different than adding in power from a power supply, separate from your controller. There are a few, basic rules to follow that will set you up for success.
Power Injection Rule #1 – Don’t Carry the Positive Between Power Supplies!
The cool thing about power is that it doesn’t have to “flow” in any specific direction through your pixels. At any point in your pixel string, you can go forward, backward, or any combination of the 2.
However, you need to be careful and follow the rules. If you’re injecting a run of pixels from your controller with 1 power supply, you can pretty much do whatever you want. You can add power in at the front end, at the back end, and anywhere in-between.
When using a single power supply, always continue the connections between all the wires of your pixels and your power supply. If you add power in the middle of the strand, connect all the +’s together, all the -‘s and all the data will flow through (not touching the power supply directly).
When you use multiple power supplies for longer runs and/or more pixels, you need to disconnect the positive (+) wire when you change power supplies. You also need to keep the negative/ground (-) wire connected through the line of pixels.
You’ll never disconnect the DI/DO (data in / data out) or negative wires down a string of pixels. These deliver the data that the pixels use to change colors, so they’re very important to your lights working 🙂
If all the information in the section above seems confusing, that’s because it is! The truth is, you can power your pixels in many different ways, but one of the very easiest ways is to use “Tees”.
Sold by pretty much all of the holiday light vendors, these adapters pass through the data and negative wires, while disconnecting and adding in your new power wire. Most often they are wired as seen in the photo – the “bottom” wire connects directly to your power, and the “data” flows through across the tee. (See my high-quality marking on this tee).
Tees are typically worth the few dollars they cost because they make it really easy to hook up your power supplies.
Most vendors will supply a wiring diagram to let you know what colored wires attach to which connections.
Any time your voltage is getting too low between strings of pixels, drop a tee in, and your voltage will be back up to full! It’s really that simple, and it makes putting up your display really easy, especially if you take down good notes for future years. 🙂
End of Line Injection
As I mentioned above, when you are using a single power supply, you can simply provide power at both ends of the string of pixels to effectively “double” the number of pixels you can power between breaks.
This can be a good option for you if you’re custom wiring your prop anyways, and perhaps it’s more convenient to where your power supplies are located to do it this way instead of via Tees.
Using A Single Power Supply vs. Multiple
If you’ve read this far, you may be asking the age-old question of “How Many Power Supplies Should I Use?”
Some folks use small power supplies, scattered around for minimum voltage drop, and others use large power supplies with many 12v or 5v cables running around.
The truth is, I could write a whole book on this topic because there are so many variables and so many different ways that you could do things. For most props and Christmas light displays, there are even many different ways that would work well. So, what should you do?
I’ve gotten into the habit of using as few power supplies as possible, when possible.
For me, the first question when I am thinking about sizing power supplies is this (and there will be a whole different post on this topic later!) – “How many props can I power within 25′ of this thing?”.
The shorter the cables are to the props, the less voltage drop.
The less voltage drop, the more pixels we can run before re-injecting power – there is a definite amount of drop that happens as you run through the wire that the pixels are on. We can’t change that. But we can change the path from the power supply to the first pixel, and maximize that for minimum voltage drop.
So, in areas that are very dense with pixels, I like to use larger power supplies. In less dense areas, I use smaller power supplies. On a smaller display, you might be able to get away with a single power supply.
But always remember to keep around some backups! You never know when you’re going to need one!