For larger projects — hundreds or thousands of pixels, or even with smaller numbers but with bright, power-hungry animation — powering through the SCORPIO board isn’t practical and the NeoPixels must be powered externally. The power source might be a 5V DC power brick, or a larger battery that can deliver ample current.
Here’s a schematic diagram of how the parts connect. It’s laid out to make all the connections clear, though the actual physical wiring will likely take a different shape…and might have JST plugs on the strips, etc.:
Again this example shows NeoPixel strips, but any NeoPixel-compatible part could be used.
The ground pins at the end of the board are no longer used for power distribution. As current needs increase, NeoPixels should tap directly into a 5V source and ground. A single ground connection between board and pixels ensures a common point of reference, but isn’t for delivering power.
The 5V DC power source for the NeoPixels might be a power brick, bench power supply, or large battery (the nominal 3.7V from a LiPoly cell is sufficient, it doesn’t really need to be a full 5 Volts). Something like a barrel jack connector might be used here for convenience.
Power to the SCORPIO board can be provided one of three ways:
- (A) above: Through the USB port, either from a USB hub, phone charger, or cutting up a USB cable to tap into the same 5V supply as the NeoPixels. This is usually simplest.
- (B): a LiPoly battery plugged into the JST connector. Perhaps for portable projects, if you don’t want to tap into the same power source as the NeoPixels.
- (C): connect USB and GND to the same 5V supply as the NeoPixels. If you go this route, unplug the power supply when connecting USB to program the board. The extra wire between NeoPixel ground and edge-of-board ground isn’t needed in this case, since everything’s in the same domain.
If it’s your first time building a large NeoPixel project, please familiarize yourself with the Power Topology page of the 1,500 NeoPixel LED Curtain with Raspberry Pi and Fadecandy guide. The key point here is to use adequate conductors for carrying power. Wires that are hot to the touch are a fire hazard and a sure indication of inadequate gauge.