Vibration motor meets the Headphone jack


Although vibration motors are common in Mobile phones, procuring button sized vibration motors were the ultimate challenge. (There were a couple of good ones on ebay, but couldn’t find one at this point of time)

But once that was resolved, one of the leads of the vibration motor was connected to the headphone jack and the ground of the headphone jack to the other lead.

Now square wave signals are played through the headphone jack using Audacity. Although one can feel the motors vibrating, using an operational amplifier such as LM324 helps to intensify the vibrations. ( Power source to LM324 – Battery/Arduino )





One of the weirdest but yet satisfying experience with the vibration motor is when you connect the vibration motor through the audio jack without any amplifier. You can hear the music being played through the vibration motor. The motors seems to be dancing to the music being played. We tried so hard to capture the phenomenon but the sound was too feeble to be picked up. That shouldn’t stop you from giving it a shot.

The ultimate guide to using LEDs with headphone jack


Lighting up an LED using the headphone jack is probably one of most easiest tasks. Take the mic of the TRRS pin ( or left in a TRS ) and connect it to the shorter end of the LED. Take the ground and connect it to the longer end of the led and you are good to go !

A potential difference of ~3V exists between the two pins that is sufficient to light up a LED. Why is there a potential difference in the first place ? Well, this will answered in great detail in one of our post on the Anatomy of a headphone jack.

Now no one wants to stop with just lightning up a LED, so let’s improvise..


Controlling LED brightness

Like we said: A potential difference of ~3V exists between the two pins that is sufficient to light up a LED.  By controlling the volume, we can reduce this potential difference and thereby dim the LED.


You can control 2 LEDs (min.) with a single headphone jack

With a simple headphone jack, one is capable of controlling 2 LEDs at the very minimum. Take 2 LEDs and connect them both to the Left/Right in the configuration shown below:


If one plays a square wave through the Left/Right then the first LED would light during the positive half of the cycle and the second one during the negative half. This is because LEDs are conductive only in one direction.

You can watch a demonstration of this in the following video.

And as a bonus, we did a frequency sweep  from 1 – 30 Hz (Square Wave) and here is how that looks:

Hang on a second!

If you can do that, then you play songs and also visually witness Beats phenomenon right? Absolutely!

Visualizing songs using LED

Beats phenomenon

Headphone jack as a switch

In all our above setups, we connected the jack directly to the LED. But one might need the LED to be brighter. So, to do that we had to bring in a operational amplifier ( LM324 ). This can be powered using a OTG (On-the-go) cable or using an Arduino.


Now using this we can use the headphone to perform switching operations. And this is what we demonstrate in the following series of videos:

Schematics/Circuit diagrams will be uploaded soon! Thank you.




LED as light sensor !!?

Sometime ago there was a post on reddit which claimed that you can use your LED as a light sensor to detect the intensity of light. We decided to try it out and oh boy! it completely changed our perspective on the LED.

We just took a LED and performed an AnalogRead on the Arduino. Check this out:

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


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

Now in our previous post, we established that the headphone jack can be used to successfully detect electromagnetic disturbances ( Sparks and Lightning ). In this post, we explore the interaction of the tube light with the headphone jack.


Here is a close up of the peak that you saw in the video:


Nowadays of course, we have moved on Non-flickering tubelights and it is highly unlikely that we might be able to detect the peculiar peaks that you see on this. But to be sure we are currently working on this and we will keep you guys posted on the results.

Also if we could incorporate this into a IoT network, things will go crazy!!!


*   Image Source

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 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

Testing basic headphone jack functions (Android)

In this post we will be trying to emulate basic functions as prescribed in the Android Documentation.  In order to understand the functions we first need to understand the circuit layout of the headphone jack which is as follows:

Screenshot from 2017-05-22 11:11:21

Now with this circuit in hand you can perform a series of tasks. This has been summarized in the table below.

Screenshot from 2017-05-22 11:03:00

This post will primarily focus on the Function A since that is the one that is commonplace in all mobile phones with a headphone jack. In the following video, we demonstrate how to emulate the following functions using a headphone jack

  • Play/Pause
  • Open Google Voice
  • Next song
  • Radio
  • Emulating Google voice

Every speaker is also a microphone!

Sometimes it comes as a surprise as a people to people when I tell them that every speaker is also a microphone. This is true because in a speaker you send in electrical signals to change the way a speaker cone moves. This in turn produces various sounds.


With the same setup, if one provides a mechanical vibration to the diaphragm, this will generate audio signals corresponding to that mechanical vibration.



We have made a video demonstrating this using a headphone jack and a phone. In order to loop the sound from the mic to the speaker in the video, we use the following command on Linux:

pactl load-module module-loopback latency_msec=1