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Chapter 7: Staying Current > Energy Monitor Hardware

Energy Monitor Hardware

For our simple energy monitor we will need some hardware both big and small beyond an Arduino-compatible microcontroller. This includes a current sensor, a safe source of alternating current, a display, some sort of extension cord or power strip, and a handful of other smaller components.

Before we get started building our energy monitor, though, let's first take a closer look at each of the main components in more detail and follow that up with a summary parts list for all the components needed to build this project.

Split-Core Current Transformer

At the heart of our energy monitor is the split-core current transformer. Also called a CT sensor, this is a noninvasive sensor that clips on to an AC power line to detect the flow of current through a wire. It does this through a process of induction: as the current passes through the wire it creates a magnetic field in the CT sensor’s ferrite core. A secondary wire winding around this core creates a smaller current proportional to the load on the wire. Remember that the Arduino’s ADC can only measure voltages, resistance, or current, so we need to combine our CT sensor with a small burden resistor to generate a voltage output that can be properly measured. The sensor we’ll be using is shown in Figure 7-1, although you might have something that looks a little different.


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