Sense Electrical Currents with Your Finger

The Thunder Finger by Zack Freedman lets users see electrical currents in real-time and feel them with a Neosensory Buzz haptic wristband.

The Idea

Some animals have the ability to perceive electric currents (also called electroreception), including sharks, cockroaches, and bees. Sadly, humans are unable to sense these invisible fields because we lack the necessary organs, at least until now. Over on YouTube, maker Zack Freedman was able to create a wearable device that allows humans to interact with the world around them in a much deeper way by displaying electric fields on a screen.

This project was born from, in Freedman's own words, "Because I slammed too many cocktails and entered Hackster.io's contest to Expand the Human Experience." If you also wish to enter the contest and use the Neosensory Buzz haptic wristband to "expand your senses," then you can join here.

Electronic Components

The most important part of this project is the sensor for picking up electrical fields and converting them into a machine-readable format. This is accomplished by using a fluxgate magnetometer to sense these fields, which then sends the values to an Adafruit nRF52832 Bluefruit Feather board via an analog pin.

This particular development board was chosen because it has both the onboard battery-management circuitry (required for making it a wearable) and can act as a Bluetooth Low Energy master device, allowing it to connect to the star of the show- the Neosensory Buzz haptic wristband.

Because this is for expanding one's own sensing capabilities, using the Wristband lets people feel the current, rather than just seeing it. And for the display, Freedman went with a simple Adafruit DotStar FeatherWing, which has a 6 x 12 array of RGB LEDs and easily mounts onto the Feather.

How It Works

Sensing electrical currents might seem complicated at first, especially when it comes to sending that data to the microcontroller. Freedman tried to tackle this issue at first by using a magnetometer, which is able to sense magnetic fields, but this didn't yield the correct results. This is where the fluxgate magnetometer is useful, because its specialized design enables it to sense electric currents with great precision. It works by wrapping a ferromagnetic core with a piece of wire and then running current through it to generate a magnetic field. Reversing the direction of the current also reverses the polarity of the magnetic field, so quickly alternating the two directions generates a pulse that cancels itself out if no other fields are present.

But if there is an external force acting upon it, then another wrapped wire or the same drive wire can be used to detect that imbalance. When used in conjunction with an analog input pin and a voltage reference (1.8V in this case), the microcontroller can tell when an electrical current is present and how strong it is.

Design and Fabrication

To make this device wearable, Freedman designed a simple enclosure in Fusion 360 that is comprised of three pieces.

At the bottom is the LiPo battery, then the Feather is stacked on top, and finally the display rests on the Feather. This whole assembly is placed onto a glove which has a wire running to the fluxgate sensor at the tip of his finger. The Wristband is worn further up on the wrist (of course) and it buzzes whenever the Feather sends it the right signals via Bluetooth low energy.

Seeing the Device in Action

As seen in the video below, being able to both see and feel the otherwise invisible electrical fields around us can be a cool experience. Combined with the fact it can be worn on a single hand and carried anywhere, there are many possibilities to further develop this device in the future.

If you want to see the code for this project, along with other documentation, then you can check out Freedman's GitHub repository.

Arduino “having11” Guy
19 year-old IoT and embedded systems enthusiast. Also produce content for Hackster.io and love working on projects and sharing knowledge.
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