1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Question for the Oscilloscope Experts

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by rsfoto, Oct 10, 2015.

  1. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,916
    Likes:
    1,097
    ONLINE
    CBB: He has the FFT option on his scope and he knows how to use it. In my opinion, it's much more useful. It puts the frequency amplitudes in bins.

    The "birdge" with some smoothing can give you a "single number".

    The "bridge" unfiltered, sort of, does "frequency doubling".

    The "thread" started with a "poorly designed" single supply circuit.

    The "thread" has been a huge learning curve for a "stubborn: OP. I believe his words. He's "learning" and not "regurgitating".

    I influenced the manufacturer to pay a bit more attention to their data sheets (unreadable schematics). They will be migrating to "TE" format just like NS migrated to "TI" format. Personally, I liked the NS format better.

    The "first stage" is important.

    A "lot" was learned from the manufacturer's application note, BUT it was not just duplicated.

    The "thread" itself is a nice demonstration of a "self-taught" learning curve".

    PS: can;t watch wmv files easily. mpeg is better.
     
    • Thanks Thanks x 1
  2. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    Will change the capturing format ;)
     
  3. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    I am trying, I am trying :nailbiting:
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico

    Above came to my mind again and I thought that perhaps for those having an Oscilloscope to integrate in the circuit a connection for a probe but also have a LED bar for those who have no oscilloscope. For these people with no Oscilloscope I can give them a SeismoVID of my column eg. tape the LED bar and then they can compare, but this idea is the second stage when I see that the circuit is more or less what I want. :wideyed:
     
  6. cowboybob

    cowboybob Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2011
    Messages:
    3,023
    Likes:
    477
    Location:
    James Island, SC
    Good idea. Have fun!
     
    • Thanks Thanks x 1
  7. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    I think that the most interesting experience will be to put the current circuit as it is (just for testing) on my columns in the Observatory and compare the reading at the Oscilloscope with the readings I know from here at my apartment in the 4th floor. That will be an eye opener for me and so I will be able to judge if all this has made sense or it was just another experience.

    I will for sure also think about using a direct integration of the Piezo sensor in the whole circuit box or connect it via wires. I do not know how good the cables are from the audio RC connectors or the Stereo cables with 3.5mm connectors. Test test and test. I can not imagine anything else at the moment. o_O

    Let us forget the parasitic 60 Hz frequency for the moment :) perhaps it disappears from itself after having soldered everything together :confused:
     
  8. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,916
    Likes:
    1,097
    ONLINE
    If the sensor is going to be far away use twisted pair shielded. Ground the shield at one end.
     
    • Thanks Thanks x 1
  9. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    936
    Location:
    Canada, of course!
    Some audio cables are shielded and block 60Hz pickup but headphones extension cords or speaker cords are not shielded and look the same.
     
    • Thanks Thanks x 1
  10. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    Next step yesterday was to take off the Antennas and wire it with one strand wires which I get from some old Ethernet cables laying around.

    Finally I saw that the circuit is not really that big as I thought :wideyed: except that HUGE 1μF Film capacitor. It will have nearly the size of the full circuit :banghead:. Is there an alternative for that Monster component ? Will try with Ceramic capacitor and see what happens ... :confused:

    Vibrar_v2_TL082_VR_Amp_FW_03.jpg

    If I go now onto a veroboard, what is better ? Directly sodler the OpAmps into it or use a Socket. I could use a DIP 2x8 socket and accommodate both Op Amp on that one.

    OK I will think it over for a while about how to solder the whole enchilada and then make my first soldered version as small as possible.

    and Surprise I just saw that the FW rectifier is not a TL082CP but it is a Dinosaur called MC34082P :D. After exchanging it to an TL082CP I did not see any difference in the outcome, but exchanging the Piezo amplifier from a TL082CP to a MC24082P there was a huge difference in that way that I have tremendous frequencies so I will leave there the TL082CP.

    Vibrar_v2.0.2_TL082_VR_Amp_FW_01.JPG
     
  11. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    936
    Location:
    Canada, of course!
    The Epcos 1uF/63V film capacitors I use are MUCH smaller that your Oriental high voltage ones. They are 0.25" long, 0.15" wide and 0.35" high with their leads 0.2" apart.
    An old MC34082 dual opamp is high speed so it will probably oscillate when used on a solderless breadboard.

    I soldered thousands of circuits on Veroboard with a very compact layouts. Each copper track was cut with a drill bit at an unused hole to as short a length as possible and only one wire was soldered in each hole.

    A ceramic capacitor picks up, sounds and vibrations.
     

    Attached Files:

    • Thanks Thanks x 1
  12. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    Thanks AG,

    will search for those Film capacitors. Well that is what I found on a specialized store here in Mexico :banghead:

    http://www.agspecinfo.com/pdfs/P/POLISTER.PDF this is what I get
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    936
    Location:
    Canada, of course!
    With C1 as 1uf and R4 as only 10k then the circuit cuts most low vibration frequencies that you want, which is why I said that R4 and R5 should be 470k and the pot should be 4.7M then the circuit will pass low vibration frequencies.
     
    • Thanks Thanks x 1
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    936
    Location:
    Canada, of course!
    • Thanks Thanks x 1
  15. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    Thanks AG,

    Just placed an order to see how it works. Ordered 10 of those caps you mentioned.

    If it works then I will order everything from there ...
     
  16. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    Hi AG,

    I do not have those components but just tested with 200KΩ on R4 and on R5 I put a 1MΩ resistor plus 1M trimpot and no change at all.

    Will keep trying on R4 a ~400KΩ resistor and on R5 a 3.9MΩ plus a 1MΩ trimpot and see what happens then.
     
  17. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    936
    Location:
    Canada, of course!
    Simply calculate the low frequency cutoff yourself: 1 divided by (2 x pi x R x C) where R is Ohms and C is Farads. This is the frequency that is cut -3dB (0.707 times and lower frequencies are half the level for each octave lower.)
    1uF with 400k is a cutoff frequency of 0.4Hz which is 2.5 vibration movements each second. The gain at higher frequencies is 1 + (2M/400K)= 6 times.
     
    • Thanks Thanks x 1
  18. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    Thanks AG,

    Farad value in this case for example when I use a capacitor with 1μF that would be 0.001 in the calculation ¿ Correct ?
     
  19. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,916
    Likes:
    1,097
    ONLINE
    1 uf = 1e-6 F, 1 nf = 1e-9 F 1 pf = 1e-12 F

    It's just easier to use engineering notation. 1 uf = 0.000001 F
     
    • Thanks Thanks x 1
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    936
    Location:
    Canada, of course!
    400k ohms is 0.4M ohms. When multiplying a 1uF capacitor with a 0.4M resistor then the u cancels the M and the answer is simply 0.4, it is that easy.
    I make it even easier. How much is 1/(2pi)? It is 0.159155.... which is very close to 0.16 so I calculate 1 divided by (2 x pi x 0.4M x 1u) as 0.16/(0.4M x 1u) which is 0.16/0.4= 0.4Hz a vibration frequency.
     
    • Thanks Thanks x 1
  21. rsfoto

    rsfoto Member

    Joined:
    Jun 14, 2013
    Messages:
    189
    Likes:
    9
    Location:
    Mexico
    Thanks KISS,

    I somehow missed millifarad :banghead:

    mF = Milli Farad seems to be huge capacitances...
     
    Last edited: Dec 20, 2015

Share This Page