NeoPixels are usually described as “5 Volt devices,” but the reality is a little more nuanced than that.
Some (not all) NeoPixel products can work with slightly higher voltages. This depends on the additional support components around the chip, based on available space, cost and the most likely application. Refer to the specific product description page for guidance on acceptable voltage limits for each type. When in doubt, aim for 5 Volts.
Lower voltages are always acceptable, with the caveat that the LEDs may be slightly dimmer. There’s a limit below which the LED will fail to light, or will start to show the wrong color.
Before connecting a NeoPixel strip to ANY source of power, a large capacitor (500–1000 µF at 6.3 Volts or higher) across the + and – terminals provides a small power reservoir for abrupt changes in brightness that the power source might not otherwise handle — a common source of NeoPixel “glitching.”
For a polarized electrolytic capacitor as seen here, the negative (–) lead is usually indicated by a stripe and/or may be shorter than the + lead.
This is an item we don’t stock, but they can be found from parts distributors like Digi-Key.
For many wearable projects we recommend a lithium-polymer battery. These deliver 3.7 Volts — perfect for directly feeding low-power microcontrollers such as the Adafruit Flora, yet sufficient for a short length of NeoPixels.
Make sure you only use NiMH cells in this configuration. Four alkaline cells (the disposable type) will output 6V total — that’s too high for some NeoPixels, and definitely too much for the microcontroller!
USB power banks can sometimes be used a couple of ways…
- Powering a microcontroller board through its USB port, tapping power for the NeoPixels from the board’s 5V or VIN pin.
- Dissecting a USB cable to provide 5V directly to the pixels.
Many USB power banks shut off automatically when current draw is low (e.g. few or no pixels lit), so this requires experimentation and isn’t ideal for all situations.
A buck converter can efficiently step a higher DC voltage down to 5V for NeoPixels and microcontrollers … for example if you have a 12V power source, like a car battery.
Different converters have a specific input voltage range and output maximum current, so check specifications carefully.
If you use a bench supply, do not connect NeoPixels directly. Turn on the power supply first, let the voltage stabilize, then connect the pixels (GND first).
Each individual NeoPixel draws up to 60 milliamps at maximum brightness white (red + green + blue). In actual use though, it’s rare for all pixels to be turned on that way. When mixing colors and displaying animations, the current draw will be much less. It’s impossible to estimate a single number for all circumstances, but we’ve been using 1/3 this (20 mA per pixel) as a gross rule of thumb with no ill effects. But if you know for a fact that you need every pixel on at maximum brightness, use the full 60 mA figure.
To estimate power supply needs, multiply the number of pixels by 20, then divide the result by 1,000 for the “rule of thumb” power supply rating in Amps. Or use 60 (instead of 20) if you want to guarantee an absolute margin of safety for all situations. For example:
60 NeoPixels × 20 mA ÷ 1,000 = 1.2 Amps minimum
60 NeoPixels × 60 mA ÷ 1,000 = 3.6 Amps minimum
The choice of “overhead” in your power supply is up to you. Maximum safety and reliability are achieved with a more generously-sized power supply, and this is what we recommend. Most power supplies can briefly push a little extra current for short periods. Many contain a thermal fuse and will simply shut down if overworked. So they may technically work, but this is the electronics equivalent of abusing a rental car.
Keep in mind, 60 mA is a worst case estimate! We’ve written a whole separate tutorial on getting things under control: Sipping Power with NeoPixels.
Excessive voltage, however, will definitely kill your LEDs.
Extra Amps = good. Extra Volts = bad.
If you go this route, the key is to have all of the ground pins among the strips connected in common, but the +5V from each power supply should be connected only to one length of NeoPixels — those should not all be joined. Every power supply is a little different — not precisely 5 Volts — and this keeps some from back-feeding into others.
Adafruit offers 5V DC power supplies up to 10 Amps. This is usually sufficient for a couple hundred NeoPixels or more. For really large installations, you’ll need to look elsewhere.
One possibility is to repurpose an ATX computer power supply. The nice beefy server types often provide up to 30 Amps. Some minor modifications are needed…Google around for “ATX power supply hack.” Note that the ATX 5V rail can be very unstable if there's no load on the 12V rail!
Even larger (and scarier, and much more expensive) are laboratory power supplies with ratings into the hundreds of Amps. Sometimes this is what’s needed for architectural scale projects and large stage productions. And occasionally we get requests for help…
Please note that projects of this scale are potentially very dangerous, and the problems of power distribution are fundamentally different than hobby-scale projects. As much as we enjoy helping our customers in the forums, they are for product technical support and not full-on engineering services. If you’re developing a project of this scope, hire a professional electrician with experience in high-power, low-voltage systems such as photovoltaics or large RVs and boats. This is no charade.
Power for large-scale NeoPixel installations is discussed further in this NeoPixel curtain guide.
The longer a wire is, the more resistance it has. The more resistance, the more voltage drops along its length. If voltage drops too far, the color of NeoPixels can be affected.
Consider a full 4 meter reel of NeoPixels. With 5V applied at one end of the strip, for those pixels closest to this end, power traverses only a few inches of copper. But at the far end of the strip, power traverses 8 meters of copper — 4 meters out on the +5V line, 4 meters back on the ground line. Those furthest pixels will be tinted brown due to the voltage drop (blue and green LEDs require higher voltage than red).
Pro Tip: NeoPixels don’t care what end they receive power from. Though data moves in only one direction, electricity can go either way. You can connect power at the head, the tail, in the middle, or ideally distribute it to several points. For best color consistency, aim for 1 meter or less distance from any pixel to a power connection. With larger NeoPixel setups, think of power distribution as branches of a tree rather than one continuous line.
For wearable electronics we like conductive thread…it’s flexible and withstands hand washing. Downside is that it doesn’t carry much current. Here several strands of conductive thread have been grouped to provide better capacity for the + and – conductors down a pair of suspenders.
(From the Pac Man Pixel Suspenders guide.)
Increasingly, microcontrollers are running at 3.3 Volts instead of 5 Volts. That’s great news for efficiency, but can present a communication problem with 5V NeoPixels. The 3.3V signal from the microcontroller may not be “loud” enough to register with the higher-voltage device. The manufacturer recommends a minimum signal voltage of 70% of the NeoPixel voltage.
There are two ways this can be addressed:
- Lower the voltage to the NeoPixels so it’s closer (or equal) to that of the microcontroller. This is why we recommend LiPo batteries for FLORA projects: 3.7V is enough to run a short length of pixels, and the microcontroller is comfortable at that voltage as well.
- Use a logic level shifter to step up the signal from the microcontroller to the first pixel.
The “Logic Level Shifting” page explains why some projects can work even without thispart.
For more info on using a level shifter with your NeoPixels, have a look at this guide.