Soundcard oscilloscope, voltage limiter

Bobafett

Joined Jan 21, 2020
6
Hello. I want to build this sound card oscilloscope: https://makezine.com/projects/sound-card-oscilloscope/

However my sound card has 1.3V inputs and the circuit in the example is made to limit the voltage to the soundcard to 0.7V (because most soundcard inputs are 0.7V).

I want to modify the circuit to allow more voltage. Can anyone suggest what components I can use to replace the diodes? The original uses 1N4148 which is a common switching diode.

I'm an electronics newbie and I'm assuming that the switching diodes in the schematic allow voltage to pass between the + and - side if the voltage goes over 0.7V. I could very well be wrong and that is the reason I ask here before making the circuit because I don't want to blow something up or start a fire. If I'm correct I need to find diodes that pass 1.3V in stead of the 0.7V.

Thanks in advance for any help.

ElectricSpidey

Joined Dec 2, 2017
1,160
Use 2 diodes in series instead of a single one.

Bobafett

Joined Jan 21, 2020
6
Use 2 diodes in series instead of a single one.

Can you explain what that does? Or maybe you have a link where I can read about it if you don't want to explain.

ElectricSpidey

Joined Dec 2, 2017
1,160
One single diode clamps to .7 volts so two in series will clamp to 1.4 volts. (aprox)

ElectricSpidey

Joined Dec 2, 2017
1,160
Like this...

Bobafett

Joined Jan 21, 2020
6
Wow, didn't know that. That means I can just use the same components. Good thing I bought extras. Thank you, much appreciated

ElectricSpidey

Joined Dec 2, 2017
1,160
You're welcome

DarthVolta

Joined Jan 27, 2015
454
What are soundcard Oscope's like compared to the $10-20 scopes on ebay ? Actually I can find out someday, I have an old soundcard, and those cheap DSO's Thread Starter Bobafett Joined Jan 21, 2020 6 What are soundcard Oscope's like compared to the$10-20 scopes on ebay ? Actually I can find out someday, I have an old soundcard, and those cheap DSO's
No clue but supposedly they are not that great. Better to get a 200-300 dollar regular scope according to some reviewers on youtube.

DarthVolta

Joined Jan 27, 2015
454
What if you take an old scope front end, and CRT, and try to make a new scope, with off the shelf chips? Does anyone try that for fun ?

For that matter I have a vaccum tube scope without a working transformer. I should examine it in more detail, and hook it up to the sig gen.

Then add on the soundcard. and see what happens on computer screen.