Making sensors come alive using the drawdio circuit

Key Insight: We took the output of the drawdio circuit and connected it to the mic pin of the headphone jack like so :

This was our key breakthrough. Having interfaced the drawdio with the computer opened a plethora of possibilities for us to play around with.


In this following videos, we have connected the pin -3 of the drawdio circuit (above) to the mic of the headphone jack and in the placeholder of R5, we insert different sensors such as the LDR(Light dependent Resistor). IR led, etc. This allows us to have an audible feedback from the sensors that are connected, making them ‘come alive’.


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:

DIY: Obstacle detector with Audible feedback (IR sensor + Headphone jack + 555 timer)

We were inspired by the buzzer that you find in mobile and laptop showrooms – the ones that produce this annoying high frequency tone if you fiddle a ‘little too much’ with the displayed product.


We use a 555 timer in its Astable mode to produce the frequency tone and couple it with a digital IR sensor module. We do this by connecting the output pin and the ground parallel to R2 in the figure.


And as a result when there are no objects in the vicinity, the system produces a high frequency tone, but when an object is introduced the sound dies out.  This is attributed to the change in resistance value.

Here is another variation of the same:

LiFi using IR sensor and headphone jack

In our previous post, we explored using the Solar panel + Led as a LiFi module. In this post, we shall be using IR sensors in order to transmit data (tones and square wave signals) wireless. The schematics of the setup are given below:


One can use this to send square wave of any frequency independently as well. This has been demonstrated in the video below

Video Demo:
Watch the video demo for a live demonstration of the working of this concept.

This is not limited to tones, one can use it to transmit raw music as well.