Shop OBEX P1 Docs P2 Docs Learn Events
Freebie: Soundcard Oscilloscope — Parallax Forums

Freebie: Soundcard Oscilloscope

Comments

  • NWCCTVNWCCTV Posts: 3,629
    edited 2012-11-09 16:21
    I think I heard about this a year or so ago. Some of the problems that were popping up was people were frying their motherboards due to either shorting something out or shooting to much voltage through the sound card connection. Not sure if that was resolved or not.
  • ercoerco Posts: 20,260
    edited 2012-11-09 17:05
    It states that you must keep the input signal under 0.7V to avoid potential damage, so a zener diode or two should be the first components in your input circuit, perhaps followed by a hair-thin fast blow fuse just for fun.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-11-10 03:34
    There are several ways to use this software safely.

    1. opto-isolated inputs
    2. opamp preamp front ends with limited peak output voltage.

    I actually have built an opto-isolated version of the 'sound card oscilloscope' interface powered via a 9 volt cell and used it for decoding IR remote controls. There is actually quite a bit one can do with a scope that is limited to about 30Khz. Rs232 serial is not problem.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-11-10 06:02
    Here is an interesting DIY front-end that will protect your computer.

    http://www.sciencetronics.com/greenphotons/?p=459
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-11-10 08:34
    Loopy Byteloose wrote: »
    There are several ways to use this software safely.

    I actually have built an opto-isolated version of the 'sound card oscilloscope' interface powered via a 9 volt cell and used it for decoding IR remote controls. There is actually quite a bit one can do with a scope that is limited to about 30Khz. Rs232 serial is not problem.

    Would you mind sharing your circuit for this? I think I'd like to give it a go.

    Jeff
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-11-10 09:15
    USB cheap-O sound card and and a USB isolatpr .....

    Peter..
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-11-10 10:29
    Oldbitcollector (Jeff) wrote: »
    Would you mind sharing your circuit for this? I think I'd like to give it a go.

    Jeff

    Darn! I knew someone was going to ask, but I have yet to locate a link for the opto-isolated version yet. I do have a printout of the schematic that I used to build it .... somewhere around here.

    I actually would prefer the better accuracy of the op amp version now. But with the opto-isolated version you can be absolutely sure nothing bad will reach the sound card or the computer internals.

    I'll have to dig a bit further. Ham Radio enthusiast are using 1:1 600ohm transformers to fully isolate the auto signals from their other equipment. If isolation is the primary issue this may be as good or better than the opto-isolators.

    Here is another op-amp solution that looks good to me.
    http://www.infinitespectra.com/howtos/soundcardtips/soundcardtips.htm
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-11-11 00:58
    Here are two more links for sound card scope protection.

    I am finding lots of solutions - op amps, zener diodes, isolation transformers, resistor networks.... but nothing about my opto-isolators. I build this back in 2005 and haven't a clue to where the plans went. Web sites come and go.

    It may not have been the best of solutions anyway because it was dependent on what the LEDs did and that pretty much restricted it to DC logic inputs of certain levels.

    http://xoscope.sourceforge.net/hardware/hardware.html

    http://www.ledametrix.com/oscope/index.html
Sign In or Register to comment.