I have recently bought a neopixel stick from modmypi and have read through the Uberguide provided by adafruit and it says that the neopixels can't normally be powered directly off of the Arduino. However, in the picture on modmypi, it seems that it is being powered solely from the Arduino. As it is few neopixels, are you able to control it via the Arduino pins?
I've ran 40 Neopixels from the Arduino's USB-supply. It worked fine. You can get into problems if you are powering the Arduino from 12V or more, as it will generate quite a lot of heat in the voltage regulator.
// Per.
Zapro:
I've ran 40 Neopixels from the Arduino's USB-supply. It worked fine. You can get into problems if you are powering the Arduino from 12V or more, as it will generate quite a lot of heat in the voltage regulator.// Per.
Are you saying that I don't need to connect it to a separate power supply like this:
mitchK:
Are you saying that I don't need to connect it to a separate power supply like this:
Basic Connections | Adafruit NeoPixel Überguide | Adafruit Learning System
Well you should use an external supply, but for a test it's fine.
It all depends!
// Per.
Yes, it all depends. How many neopixels are lit at a time, what colour, what brightness...
Max current is drawn when all neopixels are on together and showing white at full brightness. If they are all on but showing red at full brightness, that is only one third the current compared to white. All white at half brightness would be, unsurprisingly, half the current, but it would look only somewhat dimmer than full brightness because the eye is not linear. A chasing/flashing pattern might draw much less because only one in three or four neopixels is lit at any instant.
On USB power, you can draw max around 450mA. Best to stay away from that maximum. Powered by an external 7.5V psu connected to the barrel jack, you can go a bit higher, perhaps 800mA or 900mA, but stay away from that limit too.
The ideal is an external 5V regulated or switch-mode supply, like a smartphone or tablet charger, but check its current rating and stay away from the max. You can power the Arduino and the stick from this, but split the power and take one pair of wires to the 5V & ground of the Arduino and separate wires to power the stick. Thay way, the stick's current does not flow through the Arduino board at all.
As a guide, a 10 neopixel stick could draw as much as 600mA on full brightness white. On full brightness red, green or blue it would draw 200mA. On yellow, cyan or magenta, around 400mA. Other colours could be anywhere between. A chasing pattern of red where only one in four pixels is lit at any instant would be only 50mA.
Paul