Running Adafruit Feather HUZZAH ESP8266 with external power supply (3.3V / 5V)

Usually you use a usb cable to power and programAdafruit Feather HUZZAH ESP8266 via the mini usb port:

But what if you want to use external 3.3V (or 5V) power supply? To which pin should you connect it?

Connecting an external power to Battery pin or 3V pinwill damage the device (the former is connected to the charging circuit, the latter is connected to voltage regulator’s output).

Another option is to have special mini usb cable with exposed power lines but this is too expensive I think.

So let’s examine other possibilities by looking at the schematic:

AP2112-3v3 is a voltage regulator that converts input voltage to 3.3V. The input voltage can be up to 6V. This IC can be powered by external battery (VBAT) or by the onboard USB connector:

So connecting our external power to VBUS seems to be the solution. But first we need to check two things:

1) Will 3.3V sufficient to drive the board?

According to AP2112 specs if you supply 3.3V to the input, VR will output 3.3V (with very small drop):

So that’s great!

Of course you can supply with anything between 3.3V and 6V.

2) Is VBUS accessible by end users?

Fortunately yes! If you look at JP headers you’ll see that pin 3 is actually VBUS.

But where’s that on the PCB? Well, this pin is labeled USB:

Be sure to disconnect the external power supply when you program the thing.

So the final picture is:

In my case I wanted to use 3.3V AC/DC converter (likeIRM-02-3.3or Hi-link HLK-PM03 AC-DC 220V to 3.3V Step Down Buck Isolated Power).

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