DIY Osciiloscope & frequency generator

Discussion in 'The Projects Forum' started by MHDS, Aug 8, 2015.

  1. MHDS

    Thread Starter New Member

    May 25, 2015
    20
    1
    Hi everybody. I am trying to create home made oscilloscope & frequency generator. And I will use a LCD to display the waveforms. Being a newbie in electronics, I have got less ideas about how to start & how to make it. The circuits on the internet have max input of 5V, most of them. I wanna create one so that I can use it as a real one... Both oscilloscope & frequency generator. Can u please help me in this regard??
     
  2. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,648
    764
    What is your experience in electronics?
     
  3. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    Are you comfortable with soldering a few smd parts? If so, then the following kits is what I have done a couple of weeks ago.

    http://www.banggood.com/DSO138-DIY-Digital-Oscilloscope-Kit-Electronic-Learning-Kit-p-969762.html

    This scope use an ARM mcu which was pre-soldered on board. The display is a 2.4" color GLCD and max frequency to display is 200 KHz which is good for audio signals.

    http://www.banggood.com/DDS-Function-Signal-Generator-Module-DIY-Kit-Pulse-Sine-Wave-p-958215.html

    This DDS signal generator is good for up to 8MHz.

    Before making the O-scope, I have tried using 12F675 to function as a scope and the output is displayed as NTSC composite video on my home TV. Well, it worked but the display is not as good as I wanted.

    Allen
     
    MHDS, nsaspook and nerdegutta like this.
  4. MHDS

    Thread Starter New Member

    May 25, 2015
    20
    1
    I am a second year student in Electronics engineering. I have just started analysing those circuits available on the net. Particularly power supplies, sensors etc. I don't know the theory behind ICs. But I know how to use some of them. I have soldered some basic circuits like power supplies & radio transmitter.
     
  5. G-ManX

    New Member

    Jan 14, 2014
    9
    4
    I am just getting started on researching DIY O-Scopes myself. Not in any particular order, below are links I've bookmarked just this past week during my research. You have probably already visited these sites in your quest, but I posted them just in case they help.


    In addition to absf’s kit, which I had also researched, my links are primarily PC based solutions which include a myriad of ideas from a soundcard o-scope and pc software to a prebuilt sub $100 PC solution.


    You may be looking for something much more robust, so please do post back and let us know what you went with (links below):


    http://homediyelectronics.com/projects/howtomakeafreesoundcardpcoscilloscope/?p=1


    http://www.amazon.com/gp/product/B0...veASIN=B009H4AYII&linkCode=as2&tag=hdetron-20


    http://makezine.com/projects/sound-card-oscilloscope/


    http://www.zeitnitz.eu/scope_en
     
    MHDS likes this.
  6. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    Everyday Practical Electronics is running a PIC tutorial in monthly instalments, the ongoing topic is developing a LCD scope.

    AFAIK: it won't culminate in a polished design, but it goes through all the theory and tricks of the trade to get a decent sampling rate without a GHz CPU.
     
    MHDS and absf like this.
  7. MHDS

    Thread Starter New Member

    May 25, 2015
    20
    1
    :):)
    I had downloaded the zeitnitz software & in fact had also designed one similar to the simple schematics in the websites mentioned above with the recommendation of a friend. The only blunder was I gave an AC input of around 8V and didn't use the diodes. Soon after plugging to the mains, there was a bang!!!! Later the technician told me that my sound card had been shorted. Now my PC is working fine.
    After that I realised that I should know all the technical formalities before making such sensible ones.
    Hence I asked in the forum. By the way, what's the maximum input I can provide to my PC in sound care O-scope??
     
  8. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    For a PC sound card O'scope, the up limited frequency is 20Khz, that is the audio frequency original design, if you just want measure the audio is ok, if you want to measure some higher frequency then you should choose some other options.
     
    MHDS likes this.
  9. Externet

    AAC Fanatic!

    Nov 29, 2005
    762
    57
    MHDS : Prepare a budget of purchasing all parts to make real performing instruments as you want. Parts list must include cabinets, knobs... everything. Like shown in an oscilloscope service manual parts list.
    For the resulting amount of $, you should be able to buy nearly half a dozen used oscilloscopes in working condition, with schematics on service manuals included.
    Buy only one; dismantle it to pieces: Now you have ALL the exact parts needed to put one together. Then put it back together for a learning experience. Will take you about a year. Or just erase the blackboard and use it as bought... right away.
     
    atferrari likes this.
  10. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    AFAIK: that's about the Nyquist frequency - the sampling frequency must be at least double the highest frequency you want it to handle.

    The cheaper sound cards sample at 44kHz - you can buy faster if you want to.
     
    MHDS likes this.
  11. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    Since I wasn't too fussy about having the latest LCD scope - I got a Tek465 CRO for only the effort to carry it home.

    3 CROs in all - from the "Sunday best", to one I don't mind taking outdoors and using in the garage.
     
  12. MHDS

    Thread Starter New Member

    May 25, 2015
    20
    1
    Thank you. And what's the max input voltage I can provide to it?
     
  13. MHDS

    Thread Starter New Member

    May 25, 2015
    20
    1
    Umm.. Can you explain what are themeanings of Nyquist & sampling frequencies?
     
  14. tom_s

    Member

    Jun 27, 2014
    285
    333
  15. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    That is for audio CD samples rate, if you want to do that, don't you need to do from inside of the computer?

    Buy a new card just for doing O'scope, the price maybe I can buy a second hand 20Mhz.
     
  16. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    About 1 Vrms.
    I have been downloaded the Soundcard Oscilloscope in my computer for a couples years, I just want to try the effect, you can see the Use Your Laptop as Oscilloscope, there is a voltage limiting circuit inside, you can also add two voltage limiting diodes 1N4148 cross on the input of the microphone and gnd, two diodes are one for positive signal and another for negative signal, so they are put in different direction.
     
    absf likes this.
  17. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    I explained Nyquist frequency in the first line of my post.

    Sampling frequency is simply how often the analogue value is sampled and presented to the ADC.

    If the sample rate is exactly the same as the sinewave frequency fed to the converter - it will only display one fixed amplitude. In the real world there would be a little drift causing the converted value to change slowly.
     
  18. G-ManX

    New Member

    Jan 14, 2014
    9
    4
    Since folks read our old posts for learning, I thought I'd add that it is recommended to use an external USB Soundcard for soundcard type oscilloscopes rather than running it through the main internal soundcard of your PC. That way if it does become overloaded, you are only out about $2 U.S. dollars and your PC's soundcard should remain safe since it is not used as the input source.

    You read correctly, these little USB External Sound Card Audio Adapters can be had for as little as $2 US dollars with free shipping. Here is an example for sale on Amazon, but they are all over eBay as well:

    http://www.amazon.com/gp/product/B0027EMHM6?ref_=zg_bs_3015427011_5

    Also here is a complete "Instructable" providing another example of using just such an adapter for an oscilloscope and includes building a return for a test Signal Generator all from the same build (so-to-speak):

    http://www.instructables.com/id/USB-Oscilloscope-with-Signal-generator/
     
    absf likes this.
  19. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    I searched the net and couldn't find it on the EPE site. I have bought the PIC tutorial "Teach in" book but that didn't include the making of scopes.

    May be I have to wait longer for it to become older to get it free online.

    Allen
     
  20. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    Yes, I found them on eBay. Got to order at least 2 to try out the PC scope software.

    Now lots of my MP3 songs are using 3 x 44Kb/s sampling rate. Can this sound card support that?

    Allen
     
Loading...