Question for the Oscilloscope Experts

KeepItSimpleStupid · Dec 18, 2015

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.

rsfoto · Dec 18, 2015

KeepItSimpleStupid said:
PS: can;t watch wmv files easily. mpeg is better.

Will change the capturing format

rsfoto · Dec 18, 2015

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

I am trying, I am trying

rsfoto · Dec 18, 2015

cowboybob said:
The .WMV file output is a very effective demo and could be used as a comparison SiesmoVID (just made that up ) when testing someone else's site.

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.

cowboybob · Dec 18, 2015

rsfoto said:
Hi ag,

Starting next monday I will be in vacation for 2 weeks ans then take the time to set up everything soldered on a board an test it in the Observatory. I already have a copper mesh with which I will build a Faraday cage and so I will see what comes out.

Good idea. Have fun!

rsfoto · Dec 18, 2015

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.

Let us forget the parasitic 60 Hz frequency for the moment perhaps it disappears from itself after having soldered everything together

KeepItSimpleStupid · Dec 18, 2015

If the sensor is going to be far away use twisted pair shielded. Ground the shield at one end.

audioguru · Dec 18, 2015

Some audio cables are shielded and block 60Hz pickup but headphones extension cords or speaker cords are not shielded and look the same.

rsfoto · Dec 19, 2015

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 except that HUGE 1μF Film capacitor. It will have nearly the size of the full circuit . Is there an alternative for that Monster component ? Will try with Ceramic capacitor and see what happens ...

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 . 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.

audioguru · Dec 19, 2015

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.

rsfoto · Dec 19, 2015

audioguru said:
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.

Thanks AG,

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

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

audioguru · Dec 19, 2015

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.

audioguru · Dec 19, 2015

Farnell (called Newark Element 14 in the Americas) has branches all over the world including here in Canada and in Mexico. They stock everything. If I order online or by phone before 8:00PM then it is delivered to me the next morning.

https://mexico.newark.com/?pffref=h...tid=flag&_ga=1.238796036.501951113.1446840429

rsfoto · Dec 19, 2015

audioguru said:
Farnell (called Newark Element 14 in the Americas) has branches all over the world including here in Canada and in Mexico. They stock everything. If I order online or by phone before 8:00PM then it is delivered to me the next morning.

https://mexico.newark.com/?pffref=h...tid=flag&_ga=1.238796036.501951113.1446840429

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 ...

rsfoto · Dec 19, 2015

audioguru said:
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.

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.

audioguru · Dec 19, 2015

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.

rsfoto · Dec 19, 2015

audioguru said:
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 AG,

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

KeepItSimpleStupid · Dec 19, 2015

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

audioguru · Dec 20, 2015

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.

rsfoto · Dec 20, 2015

KeepItSimpleStupid said:
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 KISS,

I somehow missed millifarad

mF = Milli Farad seems to be huge capacitances...

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