Let’s first see what we need to build this project. As the center of the project, I used the Adafruit Feather HUZZAH ESP8266 board.

To measure the voltage & current of the measured device, I used an Adafruit breakout board for the INA219 sensor. To display the data, I used the Adafruit featherwing 128×32 OLED add-on, as it is very easy to use with the ESP8266 feather board.

As a test device, I will use a simple LED, along with a 330 Ohm resistor. But this could also be any DC device you are using in your home, for example a strip of LEDs.

Of course, you will need the usual breadboard & jumper wires to make the necessary connections.

Let’s now see how to assemble the hardware for this project. Here is a schematic to help you out:

First, put the ESP8266 board on the breadboard, and mount the featherwing OLED add-on on it.

For the INA219 sensor, you first need to connect the power (VCC & GND) to the ESP8266 power. For convenience, I connected the ESP8266 VCC & GND pins to the two power rails of the breadboard. Then, you need to connect the SCL pin to the ESP8266 SCL pin, and the SDA pin to SDA pin on the ESP8266.

Finally, for the LED, we need to make the current of the LED ‘flow’ through the INA219 sensor, so it can be measured. To do so, first connect pin 12 of the ESP8266 board to the Vin+ pin of the sensor. Then, connect the Vin- pin of the sensor to the resistor, in series with the anode of the LED. Finally, connect the other pin of the LED to the ground.

This is the final result: