Imagine if chefs couldn't taste, artists  couldn't see, and musicians couldn't hear.  

Those jobs would be basically impossible,  but that's exactly how things work for  

anyone building electronics. Us humans just  can't perceive electric current, except  

y'know, when we're getting zapped by it. If I  could sense the current traveling through a wire,  

I could literally poke around in my projects  and feel the power flowing and the chips  

chattering. Today, I'm going  to give myself a super power.

...right after I deal with this hangover.

[Jazzy funk tune goes "la la la la la la"]

Huge announcement: I have just  launched my Patreon campaign!  

I'll tell you more at the end, but tl;dr, give  me all your money. Link is in the description.

So check this out. Whenever electricity flows  through a circuit, it creates a magnetic field  

around the conductor. The more current flows  through the wire, the bigger and stronger the  

magnetic field surrounding it. This works the  other way too; when we cut the current through  

the wire, the magnetic field will collapse back  into electricity and send a bit of voltage in  

the opposite direction. All we have to do is  put the right sensor into the magnetic field  

and it'll tell us how powerful it is, which  in turn tells us how much current created it.

So this is a digital compass, which is  a type of magnetometer you'll find in  

smartphones and watches. This thing  detects magnetic fields themselves,  

so we don't have to wait for them to collapse  back into electricity to measure them.

So let's demonstrate. I'm going to hook  this thing up to a Teensy, of course,  

and I'll stream each axis of the compass to  this graph. You can see that as I turn it around,  

it picks up the earth's magnetic field  just fine. Watch as I wave a very,  

very tiny magnet around, and again, it  makes a huge impact on the readings.

So I'll put this wire over it and run some  current through it, and it doesn't make a dent...

...actually it does. The resolution' s not great,  but this thing totally picks up the current  

traveling through the wire. I really should do  the experiments BEFORE I write the episodes.

We're going to need a more sensitive sensor.  Another option would be Hall-effect sensors, like  

the ones I use to detect my fingers in this data  glove. Those won't work either, unfortunately;  

you can absolutely buy Hall sensors that can  detect super-small DC currents, but you have to  

put a ferrite ring around the wire to concentrate  the magnetic field on the sensor. I can't clamp  

a sensor over a wire and a circuit board,  because the wires are... in a circuit board!

[Goofy-style G'HYUCK!]

What we need is a fluxgate magnetometer. That  sounds like some star trek bull[REDACTED] but  

trust me, it's a very real and very precise  magnetic sensor. This is a Texas Instruments  

DRV425 fluxgate magnetic-field sensor.  We just power it here, ground it here,  

this is our reference voltage, and this voltage  is proportional to the strength of-vuvuv the of the  

magnetic field... the strength of the magnetic  field... all right, I'm done with this scene.

You can clearly see that when I turn on the  power through this wire, the fluxgate picks  

up that very faint magnetic field. As I turn up  the juice, the reading increases in proportion.  

The fluxgate itself is just a tiny piece of  magnetizable material wrapped in two coils of  

wire. The drive coil magnetizes the core with  an electric current and then shuts off. That  

magnetic field collapses back into an electric  current, which is picked up by the sense coil,  

and the device measures it. Then the  drive coil magnetizes the core again,  

but in the OPPOSITE DIRECTION. It shuts  off, sense coil measures again. So,  

back and forth it goes, creating a magnetic  field, allowing it to collapse, measuring it,  

creating the opposite magnetic field, allowing  it to collapse, and measuring that too.

So these readings should be symmetrical; in  fact, we should always get the same amount  

of current out of the sense coil as we put in  through the drive coil because, like, y'know,  

where the hell else is it gonna go? But if  we expose the sensor to a magnetic field,  

heh-hey hey! The field helps the drive  coil in one direction, so it charges the  

core faster and returns a higher reading. The  field FIGHTS the coil in the other direction,  

which prevents it from charging the core  all the way, and it reduces the reading.

It's just... a current transformer... in disguise.

[Palpable awkwardness]

...arright...

This thing is sensitive enough to pick up the  faint magnetic field around a current-carrying  

wire with, like, a really high level of accuracy.  By measuring the difference between the readings  

in each direction, we can tell not only how  powerful the magnetic field, is but also which  

direction it's pointing. In this sensor the core  runs from the left side to the right side, so it  

detects current on wires going from the top side  to the bottom side. That's because current follows  

a right hand rule, so if the current is flowing  thiiis way, magnetic field forms thiiis way.

By the way, I usually skip over the theory, but  in this episode I decided to mix it up and dive  

a little deeper. Did you enjoy learning a bit  about electromagnetism, or should I just shut  

up and jump into the project? Did I do a good job  of explaining this stuff? Drop me a comment and  

roast me up real good; I am still trying to find  the perfect blend of education and "education."

So for this project we're NOT using a Teensy!

[Gasps from live studio audience]

We are using the Adafruit NRF52 Feather because  it integrates the battery circuitry that we need  

to turn this into a wearable. This thing also  acts as a Bluetooth Low Energy master device,  

which is important, because it lets us connect  to this Buzz wristband. I am using this vibrating  

wristband instead of, just, you know, adding  vibrating motors to the project, because drunk me  

drunkenly entered a developer contest on Hackster  and if I ghost them one more time, they're gonna  

stop sending me free hardware. I tried to convince  the company that makes this, Neosensory,  

to sponsor this episode, but the CTO called the  hell out of this bluff.

Enjoy the free PR, Scott.

All right, so what the hell is this  thing anyways? Well, out of the box,  

the Neosensory Buzz translates the volume  and pitch of incoming sounds into vibrating  

patterns on these four rumble motors. It lets  you touch sound. If you're hard of hearing,  

this sensory substitution can improve  your lip reading and alert you to cars  

skidding out of control behind you.  If your hearing is fine, it's...  

it's kind of useless. But I guess it makes  your speakers sound like a bass booming rave?

[Tacky 90's trance]

[Oontz oontz oontz]

[Trance still playing in background]

Give this thing to Elon Musk and throw  them in a closet with three tabs of acid,  

he'll get us to Mars in like 20 minutes.

All you have to do is call some functions and  the Feather connects straight to the Buzz,  

overrides the sound-to-vibes functionality, and  directly tells it when it's ready to rumble.  

Somewhere along the way, fun fact, your sketch  has to agree to Neosensory's terms and conditions.  

I Am Not A Lawyer, but I really doubt that you can  sue an embedded device when it breaks an end-user  

license agreement. It does this by literally  saying the word 'agree' over Bluetooth serial.  

Somebody overthought the HELL  out of this and I love it.

This thing's really simple to build. We  just wire the sensor up to power and ground,  

we run the output and reference pins to the  Feather's analog inputs, we tell the thing  

to vibrate when the thing senses the thing, and  there we go! I can now feel electric current.  

I mean, like, you have to trust me on that; uh,  you can't feel anything through YouTube. I wish  

I wish you could, though. I'll tell you  what... uh... put your phone on your wrist,  

and on the count of three, I  will turn on the current and you  

shake your phone around. Desktop and TV  people, like, I don't know. Figure it out.

One... two... three...

[Buzzy mouth noises] [bvvvvvvvvvvvvvvvvv]

Fine. We'll visualize it too. Here's  an LED shield - I mean an Adafruit  

DotStar Matrix FeatherWingâ„¢, all rights reserved.

Ermegerd, merchernical erngernering!

I fired up Fusion 360 and I modeled a nice  three-part enclosure that glues right onto  

this weightlifter's glove. This is actually  the leftover glove from the Somatic project,  

which is why you should never throw anything away,  

ever. This sandwiches the boards and braces the  battery, so we avoid some lithium-splosions.  

I'm going to glue this onto the glove  with some E6000 and screw it all shut.

Now, we gotta make the wearable sensor  wearable. Magnetic fields weaken with distance,  

so I designed this little ring that exposes the  sensor so we can really mash it into the wire  

we're measuring. I printed this in flexible TPU,  which makes it a lot more comfortable to wear,  

but also lets me design a little pocket  to snug the sensor board in there.  

I add a little cable management on the fingernail,  so I can route the wires gracefully over my hand.  

It's important to leave some  slack so I can bend my finger,  

so I printed this little clippy dingus to  keep the wires from snagging on protuberances.

I will just display a simple  linear plot of current over  

time and add some flamboyant color  coding to make it camera-friendly.

[In the manner of an elevated individual]  Now you can, like, see what I feel, man.

Electronic status: Done. The code is also  done, but my analytics show that about 30%  

of you people run away as soon as I put a  line of code on screen. You can download it  

yourself and see what it looks like. Links  to everything are down in the description.  

I will give you the spoiler  though... it looks like code.

[Triumphant music] All that's left is to give this thing  a name! Ladies, gentlemen, and cyborgs,  

say hello...

to the THUNDER FINGER! [Record scratch]

I REALLY suck at naming things.

So we're powered up, linked up, locked, loaded.  there's a chance that I'm currently the only  

homo sapiens capable of feeling direct  current. Let's finger some electrons!

This thing actually works alright for a ten-hour  project. It isn't as sensitive as it should be,  

but that has more to do with the deadline than  the hardware. If I had some time to tweak,  

I could calibrate the DRV425's response  range to better pick up what I'm looking for  

you. I could also feed the output reference  voltages into a differential amplifier,  

which would increase our resolution. Also,  I'm polling the sensor super-slow because  

it makes the code easier to write, but we can  actually read the fluxgate up to 23,000 times  

a second. With the right code, we could decode  PWM pulses, we could pick up audio transmissions,  

we could even sniff 9600-baud serial  traffic. I could convert each one  

to a different tactile texture so I can  debug and hack electronics with my finger.

This finger, in fact. This one.

Of course, the Thunder Finger's vibrating  motor should really be thundering my finger  

but not my... wrist... but come on, the Buzz  was free. It's free hardware. Speaking of,  

I am putting a link to the Hackster Neosensory  contest in the description, because Hackster  

has promoted a bunch of my projects, so it's  about time I return the favor. There's still  

two weeks left in the contest. I'm looking forward  to getting stuffed by each and every one of you.

If you want to build the  Thunder Finger for yourself,  

I'm putting the links in the description.  

I'm pretty sure you can actually buy all the  parts for this project, so knock yourself out!

Big announcement, my Patreon campaign is  live! The super-duper-rad perks include  

a monthly Q&A stream, sneak  peeks at upcoming projects,  

Brooke's trolltastic blooper reel. I need your  support to buy parts and make awesome projects,  

so if you want to see more videos, it would  totally rule if you can kick in a few bucks.  

My glorious Lab Patrons get access to the  top-secret supporter-only channels in the Discord,  

which has 2,600 friendly members and  five jerks. It doesn't make any money,  

but it does make friends, and isn't... isn't the  real money the friends you make along the way?

...No, it's money. You  can't pay rent with friends.

Thanks for watching, and  I'll feel you in the future!