Using PC sound card as oscilloscope

[localbuyer]

I found a few free programs that use PC sound card as oscilloscope. I am
interested in using it to check the servo pulse. However, the logic high
is about 5/6 V and is too high for the sound card.

How can I scale down the input so it won't blow up my PC?

Thanks

[rjet]

I use the line level input of my sound card for reading 5 volt waves all the time without any problems my card is a creative soundblaster PCI-128. If you really want to drop the voltage you might just want to use like a 10K ohm resistor in series since the "line in" impedance is probably around 10K ohm already.

[clipclop]

Most soundcards dont give a very acurate signal display, this is a better opption :- http://www.xs4all.nl/~jwasys/old/diy2.html , its a logic analizer program useing the parrallel port 8 ch display.
I would play it safe and use the second interface cct with the buffer.
Stewart

[Eric Brouwer]

The simplest is to make use of a voltage divider.

Input ---/\/\/\/\------|--------------- to soundcard (L or R signal)
47K /
\
|-->/ 10K Multiturn pot
| \
| |
Ground -------------------------------- to soundcard (ground)

Use the pot to calibrate the signal. I have set it up to give out 0.5V reading with a 10V input.