As previously discussed on Bits & Pieces, the Yún – designed in collaboration with Dog Hunter – is based on Atmel’s popular ATMega32u4 microcontroller (MCU) and also features the Atheros AR9331, an SoC running Linino, a customized version of OpenWRT. The Yún is somewhat unique in the Arduino lineup, as it boasts a lightweight Linux distribution to complement the traditional microcontroller (MCU) interface.
Key features of Akellyirl’s project include a WiFi connection to facilitate continuous monitoring, TEMBOO for cloud support (with Google APIs), as well as automatic recording and writing of power consumption to a Google Drive Spreadsheet (+ analysis).
“A nice feature of this project is that the monitoring is flexible and completely wireless (except for the current transformer of course),” Akellyirl wrote in a detailed Instructables post. “This allows continuous monitoring from a PC or phone and permanent storage on the Cloud.”
To build the above-mentioned electricity monitor, Makers will require the following components:
- Arduino Yún (ATmega32u4)
- Current transformer (e.g. SCT-013-030)
- 2 x 10kOhm resistors
- 1x 47uF capacitor
- Some wires, breadboard
- 5V power supply for the Yún (smartphone charger)
“The circuit is actually very simple. It consists of a voltage divider to bias the ADC of the Arduino to a DC voltage, [with a] voltage output current transformer adding an AC voltage proportional to the AC current flowing in the cable. The capacitor forms a low pass filter with the resistors to remove noise,” Akellyirl explained.
“[Meanwhile], the current transformer produces a current proportional to the current flowing though it’s magnetic circuit. The proportion of the current in the cable that you get in the transformer is equal to the turns ratio. [For example], 30A corresponds to an output voltage of 16.67mA x 62 Ohms = 1V (rms).”
Interested in learning more about building an Arduino Yún-powered electricity monitor? You can check out Akellyirl’s detailed tutorial over on Instructables.