Wireless Drawdio circuit

                           Humans as elements of a circuit


Humans are amazing antennas!

Humans as antennas is an established paradigm and the works on Body Coupled Communications(BCC) and Personal Area Netwok (PAN) from the MIT media lab are at the frontiers of innovation based on this concept. Their works get into the technicalities of such a communication such as protocols, circuit design, etc. The only down side being that, the technology is inaccessible to the common man. If you still want to experiment with it, we have something that could get you started.


In this post, we connected the headphone jack’s mic wire to the human body and used it to transmit and receive signals through space – Wireless!

Why the headphone jack ?  Why not? Not only is it something that is readily accessible, it also does not require additional hardware.



In this post, we demonstrate this idea by turning the drawdio circuit made by Jay Silver using the 555 timer ‘wireless’ by using the human as an antenna.

In order to make the drawdio circuit (see diagram below) wireless, take out R5 and place your hand instead to complete the circuit.



Hook up a headphone jack to your computer and listen to the signals received on your mic. Your body will act as an antenna and you will be able to receive the signal on your computer. Make sure to adjust the gain of the microphone accordingly.

(see our post – Preparing a headphone jack for hacking to know how to set up your headphone jack in order for this to work)

Now if you are aware about common grounds then the above video might not seem as appealing because the drawdio in the above case by powered by an Arduino connected to the computer which is receiving the audio signal. The same concept does work with different grounds as well as we demonstrate in the following video where the drawdio is powered externally through an OTG cable.

If you would like to transmit the drawdio output in the RF range instead, one can hook up the output of the drawdio to a crystal oscillator and touch the output wire of the crystal oscillator instead.  In this video, a 32 MHz crystal oscillator is used and a FM radio app tuned at 96MHz is used to pick up the drawdio signal. This would be another way to demonstrate the idea of using the human body as an antenna.*

Instead of the drawdio, if you would like to transmit serial data from the USB port wireless, we can play the same game. Just place your hand on the TX pin of the USB-TTL and listen on the mic of the headphone.


What can you do with this ?


There are obvious limitations of using a headphone jack for BCC rather than something more dedicated as explored by the folks at the MIT media lab,  this post is an exploration on how one can intuitively achieve this using the headphone jack.


*There is a great chance that many of you might have already tried this out in your car at some point.

** More explorations on the drawdio circuit click here

** More explorations on the headphone jack click here.







The headphone jack meets an actual spark gap!

So, we had the opportunity to test out the headphone jack with an actual spark gap and it was absolutely wonderful. Check it out:

With the data we can actualy find out the frequency of the spark occurrence. In our case it turned out to be ~ 34 – 36 Hz. And since this is in the Audible range we can actually hear this (somehow we missed this when making the video)

Screenshot from 2017-06-10 20:01:07

Audio file : GoogleDrive


Part – I – Lightning detector with a simple headphone jack

Part – II – Detecting switching ON/OFF of Tube Light using headphone jack

Part – III – Cigarette lighter spark detection using headphone jack


Lightning detector with a simple headphone jack

Okay, this probably one of those posts that is ecstatic to draft because of the shear wonder that it encapsulates. We captured lightning using nothing more than just a mere headphone jack and its so simple that anyone around the world with an access to an old headphone jack can do it too!



Take an old headphone jack and strip off the mic part and you are good to go OR if you have a dedicated USB sound card you can use that!



Sparks of any kind produce electromagnetic disturbances and it is these disturbances made by lightning that we will be detecting. That is the reason we are stripping off the microphone from the headphone jack and keeping only the wire.  The wire will act as an antenna to pick up the signal.

Just to be clear, this is NOT related to the sound of the thunder by any means.

Test with Gas Lighter

Before we test the headphone jack with lightning, we needed to know how the headphone jack reacted to sparks and how a spark looks like when recorded with a headphone jack.

Since gas lighters are capable of producing sparks, we thought that it would be a great place to start. Here’s what we observed:

** Although we use a USB sound card in our videos, this works with an ordinary TRS/TRRS headphone jack as well.

Capturing lightning

Now that we have a good idea of what is going on with a gas lighter, we can predict a similar pattern with a lightning as well. Why ? Well, because lightning is the same phenomenon but, at a much bigger scale.

How do you do it ? First things first, to state the obvious one needs lightning. But besides that the setup is similar to the previous one except that unlike the gas lighter, we have to use the human body as an antenna by holding the wire coming from the mic pin of the headphone jack in our hand

Processing the recording

The audio file that we acquired has been uploaded to Google Drive (links below) but we strongly suggest that you try it out yourself to get a feel for this powerful technology that many people disregard as quotidian.

This is how the raw audio file might look (recorded with Audacity):

Now we amplify this signal on Audacity. (Effect –> Amplify)



Now you see these three prominent peaks, now these are for sure caused by the lightning. How are we so sure? Well, we were able to visually validate the data. What are those other peaks ? They are lightning too (!!!), but ones that are happening at a distance (probably many kilometers away).

Now in order to be completely sure, we repeated the same experiment another evening.. And here’s what we got:

Screenshot from 2017-05-18 10:05:53

This was a much more dramatic day with lots of lightning! ( as is evident from the numerous peaks )

How cool is that you can something as simple as a headphone jack to procure information about lightning that is probably happens kilometers away. This was absolutely ecstatic!

What does one peak look like ?

Here is a close up of one peak that was recorded:


Sampling rate: 44100 Hz

Screenshot from 2017-05-24 12:43:23

Sampling rate: 384000 Hz

This resembles very closely to a Guassian Wave packet . ( In physics, a wave packet (or wave train) is a short “burst” or “envelope” of localized wave action that travels as a unit )


We believe that the electromagnetic disturbance that is detected during a lightning / spark is a Gaussian wave packet.  (If you believe otherwise let us know why by pinging us at 153armstrong@gmail.com or in the comments section)


Video Demo:

Will be uploaded soon! (subject to environmental weather conditions ;P)

If you found this post interesting, check out

Part- II-  Detect switching ON/OFF of Tube-light with a simple headphone jack

Part – III – Cigarette lighter spark detection using headphone jack

Part – IV –  The Headphone jack meets an actual spark gap!!!!!!

Thunder Audio file (44100 Hz): GoogleDrive link

Thunder Audio file (384000 Hz): GoogleDrive link

Simple Mobile Phone Detector using headphone jack

Mobile phones send wireless signals to the nearby station in order to help you send your message or connect with another phone.

But the best part about this is that these signals can be captured whether or not you have a mobile phone or not.  And the even cooler part about this is that this can be accomplished with nothing more than just a simple headphone jack connected to your laptop/phone.


There is nothing at all you need to do besides sticking a headphone into your jack and placing a mobile phone nearby.  Then open Audacity and record it at the maximum sampling rate possible on your soundcard. That’s about it !

Video Demo:


This works remarkably well with older phones (that still use the 2G spectrum), but unfortunately we are still unable to crack into smartphones (that use 3G or 4G spectrum. Argg.. ) using this technique.

But that being said, we are trying our best to crack in. Would highly appreciate any input on this whatsoever. Have a good one!


More interesting stuff:

Sound of the dialup modem