Hello I'm NEW with Arduino and I've been struggeling for few weeks trying to figure out how to plan this first project of mine.
I want to make an RGB macro keyboard using an arduino pro micro, which consists of 9 arcade buttons that have a Neopixel ws2812 LED inside of each one them.
It will be connected to my computer executing commands triggered by the buttons, and also showing some lighting effects by the neopixels which are chained to each other (shown here)
The 9 neopixels draw a little bit more current than the pro micro can supply, thus requiring an external
power supply. Here's a similar project I'm learning from. They've managed to avoid using any cables running from outside powering it. However I don't want to constantly recharge a battery or use bluetooth. I wish that I could have only one USB Cable from the computer powering both pro micro and the neopixels, also sending the signals from the buttons to the computer. Maybe it is possible if involving a battery somehow. Do you have any ideas ? VERY MUCH APPRECHIATE YOUR ANSWERS!! AND AGAIN I'M A BEGINNER!! 
You can draw 500mA from a basic USB port without any special work. Assume the Micro takes 40mA or so (remove its power LED, or remove R5 to save 20mA). Can you manage your RGB LED's to stay under that total power consumption?
I would imagine the answer is "yes". So then you can power the LED's from the Arduino's 5V pin when on USB power.
How much power to run the neopixels at 1/2 brightness or less?
Looks interesting. Just watching the thread.
MorganS:
You can draw 500mA from a basic USB port without any special work. Assume the Micro takes 40mA or so (remove its power LED, or remove R5 to save 20mA). Can you manage your RGB LED's to stay under that total power consumption?I would imagine the answer is "yes". So then you can power the LED's from the Arduino's 5V pin when on USB power.
GoForSmoke:
How much power to run the neopixels at 1/2 brightness or less?
Well I guess cutting down the brightness to half would be OK. But... That's such a simple, though effective, solution. XD
For example let's say I'd like to have 20 neopixels. What's then? I can try to throw some theoretical ideas:
A battery that is being charged all the time from the USB, powering the neopixels. Or just actually using bluetooth to communicate with the computer as well as an external PSU, so you'll only have that one cable and not the USB. Just trying to find the best overall idea and only then getting down to the details.
Sorry but the half power for neopixels won't be so easy. With ordinary leds you can use more resistor to truly use half power but WS28xx leds use PWM so when they're ON they are all the way ON.
You would have to light at most half the pixels at any one instant so the total would be at most half.
The datasheet for your neopixels (come in different sizes) should tell you the maximum current (mA) the use.
GoForSmoke:
Sorry but the half power for neopixels won't be so easy. With ordinary leds you can use more resistor to truly use half power but WS28xx leds use PWM so when they're ON they are all the way ON.
Really? With the recommended capacitance, the PWM cycles will be averaged. Half brightness is half current (well, not quite, due to the human eye's response curve.)
SpookyHeaD:
Well I guess cutting down the brightness to half would be OK. But... That's such a simple, though effective, solution. XD
For example let's say I'd like to have 20 neopixels. What's then? I can try to throw some theoretical ideas:
A battery that is being charged all the time from the USB, powering the neopixels. Or just actually using bluetooth to communicate with the computer as well as an external PSU, so you'll only have that one cable and not the USB. Just trying to find the best overall idea and only then getting down to the details.
20 Neopixels is just fine, so long as you do the calculation to limit the current. The FastLed library can even help you out there, with an automatic current limit.
I have one project with 412 LEDs. Theoretically they can draw up to 18A. But I only have an 8A power supply. All of them on max-white will overload the supply. But 90%-all-white is just fine.
Can you plug in two USB cables? Then you can draw 500mA from each of them.
Unless you are outdoors, 9 LEDs on max brightness is going to be too bright. That would be like staring directly into your desk lamp. For practical uses, you will have very low brightness settings and you can run many, many LEDs in your keyboard.
MorganS:
Really? With the recommended capacitance, the PWM cycles will be averaged.
I will take your word on that given your 412 led project results that I never would have guessed.
Can you plug in two USB cables? Then you can draw 500mA from each of them.
Or use a 1A or 2A USB turbo phone charger. I have a 3A USB supply for my RPi, never see the low power symbol, it ran me about $15 through Amazon.
Run 5V and GND directly to the led strip and the Arduino with a source that will not be drained enough for the 5V to lower and cause problems with the AVR. If you need 1A then get 2A or 3A, the more the PS loafs the longer it will give nice clean power.
I have bought and gotten from an eBay seller some use out of OEM adjustable switching power supplies in the 30W range that do work well. They can be adjusted to higher V than desired then regulated or converted down to 5V if there's any concern about adjusted PS voltage varying with load.
I tested a buck converter with one, fed it metered 5.1V and 5.0V came out of the converter but I did not run a full set of tests that most any EE would likely do.