Usb power Teensy 3.6 and small WS2812b strip

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MrGeen

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Hi everyone,

I am planning to build a midi usb sequencer and I want to use 16x WS2812b LED's as indicators.
Since a single usb can only supply up to 500mA, the LED will have a low brightness so that the total device should need around 400mA.

To power the Teensy and LED's (and getting data), I am thinking to use a y-cable where the data+power connections will go from PC to Teensy and then to use the power-only connection to feed current to the LED's.

Could something like this work? Because I'm not sure if the LED's will get power in this way.

Thanks in advance.
 
Not sure whether I understand you correctly. Do you mean to say that the MIDI USB sequencer will consume ~400mA so that only ~100mA is left over for the 16x WS2812B LED's?

Anyway, powering 16x WS2812B LED's from a single 500mA port will definitely be bright. If you use the FastLED library for driving the LEDs and use the "FastLED.setMaxPowerInVoltsAndMilliamps(5, 500);" function then you don't have to worry about calculating the correct brightness.

A USB Y-cable [the one with 2pcs type A connector] will allow you to get power out of 2 USB ports and hence give you 1000mA.

Paul
 
Sorry, I reread my message and it was indeed not clear what I want to do.

So, the 16x WS2812B LED strip needs around 300-400mA to be bright enough but the Teensy can only supply up to 250mA (because of heat I assume). Because of that, I thought to directly use the USB voltage that also goes to the Teensy.
Im not sure if I can use the vusb pad to get that desired current (300-400mA) or that I must use a wire that is split of from the powerline of the USB cable (thats where the y-cable comes in).

The rest of the sequencer is basically just a couple of buttons and potentiometers so I guessed that this would be around 100mA max.
 
The Teensy on the Vin pin provides the full USB power that comes via the USB connection. So you can draw up to 500mA for USB 2.0 (minus what the Teensy and other components need).

The issue you will find is that even though you might "theoretically" only need a total power budget of less than 500mA, but while developing you potentially will have code bugs that will have your LED strip draw maximum power at full brightness way above the 500mA (you might damage your Teensy, or even worse your laptop / PC assuming they do not have proper safety fuses built in).

I had a similar question on a project I am working on (see here) and in the end I decided to power the LEDs via a separate power supply even though the total power budget needed would be within the 500mA USB 2.0 offers. Once my code is stable 99.7%, I might switch over to USB power only.
 
Thanks all, so I can use the Vin pin to power the LED strip. But in the mean time, I will just use an external power source until I am certain that my code is stable.
 
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