Sunday, 24 July 2016

Poor student's sound card Oscilloscope

Every electronics enthusiastic feels a need of oscilloscope . Mostly when working on switch mode circuits or the signal circuits.
Oscilloscopes are very costly even most entry level scopes.
So I decided to make my own basic scope.

Here We have used a external USB sound Card and a computer software.
Download the software from this link

How it Works
Our voice signal is an analog signal . a microphone receives it and sends it to the soundcard . The sound card has a built in analog to digital converter. then it sends the digital information to CPU for processing. Here the software processes the information and displays in a graphical user interface .


Make the signal Probe

Sound Card are normally very sensitive to input voltages . Its input voltage must be limited to 0.6 to 0.8 volts for safe operation. there we have used resistors to drop input voltage to a safe limit. the variable resistor is used to vary the input gain. here we have two diodes back to back for safety. If any cycle positive or negative has an output more then 0.7 volts one of the diodes turns on and bypasses the current keeping the soundcard safe. I have used here cheep chinese USB sound card rather than my costly internal card. There is a option of source select. you can use an headphone microphone jack to give input to internal sound card.


 c1 is optional.

Here I have used arduino fed program to generate an pulse width modulated signal.


Here is a video demo.