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9 hours ago, Eland said:

I wanted to post a quick update on my timegrapher. All together I encountered a lot more difficulties then i thought. I screwed up the amplifier assembly kit  by using blunt wire cutter and thereby accidentally ripping the conducting layer of the board as i tried to clip the wire of a resistance.

I also have the hardest time soldering the brass pin onto the piezo element. I broke several piezos by applying to much heat an bringing the ceramic layer to crack .

I'll visit a good friend of mine in January who is a electrical engineer and we'll try to get it done together (using his professional equipment).

Until then I wanted to ask @24h if you have any special techniques u used to establish the connection between the pin and the piezo and also if you could elaborate why you used a rubber casting around the pin. I thought it might rather weaken the vibrations and therefore the signal.

at least I am making a little progress with my timegrapher stand. Here is a picture of my first built (which is not functional because there is no piezo on the end of the pin):

Looks good so far!

1. For the same problem you mentioned, I did not solder the pin onto the piezo. Instead, I used a two part epoxy. I believe it was J-B Weld steel reinforced epoxy.

2. The rubber is to reduce vibrations transferred by the rest of the timing stand to get a cleaner sound. I used a vehicle fuel hose with an inner diameter just big enough for the pin to slide in and out but small enough where there isn't any extra space.

Edited by 24h

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So I managed to get everything together and got my first readings using a standard stereo pre amp I bought for a turntable several years ago. Sadly i still didn't manage to get my diy microphone preamplifer kit  to work (the one i mentiont in one of my earlier posts).

At the moment I think about ordering a already built preamplifier board but I do not have the qualifications to judge with would do the job (or at least would lead to better results then with my current solution.  That's why I am again counting on your help.

There are some pretty cheap options but I don't know how to judge the all over amplification from the specifications given.

My current preamp has the following technical specifications:

Input Impedance 100kOhm, 5mV, Output Impedance 100kOhm, 250 mV, S/N-Ratio: >50 db, 12V DC, 100mA

The options I'm most into at the moment is something like that cause its cheap and and may be an improvement (however I'm not sure about that)

https://www.ebay.de/itm/TDA2030A-Audio-Power-Amplifier-Board-15W-AC-DC-12V-Assembled/292336674126?hash=item44109fa54e:g:nUAAAOSwKrhVZbo1:rk:28:pf:0

or even simpler:

https://www.ebay.de/itm/TDA2030A-Audio-Power-Amplifier-Board-15W-AC-DC-12V-Assembled/292336674126?hash=item44109fa54e:g:nUAAAOSwKrhVZbo1:rk:28:pf:0

There are more fancy options like https://www.gearbest.com/other-accessories/pp_009478010615.html?wid=1433363

or https://www.gearbest.com/other-accessories/pp_009478010615.html?wid=1433363

but I have absolutely no clue if they would be suitable for the task at hand.

The thing is that (as you surely have noticed by now)  do not know the first thing about electronic. But I'm eager to learn, I just don't know where to start. So thank you for your time cleaning my mess.

 

On the bright site as I said, I managed to get my first signals and I'd link to share some pics of that:


20181213-185647.jpg

20181213-202012.jpg

JF-Explorer-V2-Update1.png

Junghasn-Meister-Agenda-4.png

This is my set up at the moment and some readouts from two of my watches (I hope it's okay to post the watch-o-scope screenshots). Today I broke the piezo trying to replace the cabels between it and the jack with shilded ones and now I have to get some more piezos to get my DIY-timegrapher running again.

Let me know what you think and thank you very much!

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Good job Eland. Congratulations, you are doing a good job. And do not despair about the broken discs ... I have already lost count of how many I have destroyed, due to excessive heat, excessive force, etc.
It could be that my response is a bit hasty, but I'm sure you do not need any of the devices that you indicate in the links. they are all POWER AMPLIFIERS. And what you need is a pre-amplifier. And seeing what you used in your project, I would consider that what you need is accurate and nothing more. It is possible that some modifications could be made but they would be minor. I would like to ask you to share an on-screen capture of the waveform to determine the level of the signal you are getting. I send you an example of what I am requesting.

Captura.thumb.JPG.283a421dd31dac3808159c9fe5cd14f8.JPG

 

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Good job so far! I'm interested to hear some recordings of your audio...you can upload to mega.nz.
I have a different type of pre-amp in my possession (after waiting a long time for shipping from China), but haven't had much time to get all the tools out to solder something together.

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So I uploaded 30s of recording with audacity and here is the pic of the scope mode.

https://mega.nz/#!ymwkgSBK!mKWtU5Fb1pkmGIfhzpKqZ8SXCfBZnMbnUjjwrhA7PxM

I also made some little improvements to my telegrapher stand like using a shielded cable for the short  part between the piezo and the 3,5mm jack. Alos I added a copper plate to the back for addition shilling.

 

Junghasn Meister Agenda 7.PNG

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Good job Eland. Excelent sound. I have already done an analysis of the waveform and it is excellent. It's like music to my ears. I think that with that level of sound and editing programs can do a good job. Congratulations.

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I'm analyzing the recording. And I have some observations. The first is that I can think that some buzzing of the 50 hz network is affecting although it is low with respect to the level of the signal. But when analyzing the gradation, in the second 26 drastically disappears a buzz that corresponds to very close to 90 hz. By doing so, the signal is cleaner. If you can determine what causes it, the signal will improve. I get the feeling that the stand of the microphone is not sufficiently padded and the vibration of table or desk that could be the vibration of the fan or the hard disk are transferred to the microphone.

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Thank you for all the commendation and thank you very much for your analysis @guidovelasquez !

What kind of editing would you recomand? At the moment I simply use the "narrow" filtering from watch-o-scope.

I did not completely understand your last post. What do you mean by 50 hz network?

I will try to pad the stand more efficiently! I life close to a very busy road and sometimes the whole table vibrates if a truck passes by. Maybe thats an extra factor apart from HD or Fan noises.

 

 

 

 

 

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If I could chime in on soldering piezo elements.

1) Use plenty of flux.

2) Use leaded solder.

3) Use plenty of flux :D

I have also used solder paste in the past, which has flux built in, but this is not necessary. Search ebay for "mechanic solder paste".

The trick is to prepare everything in advance, work fast, since the element is heat sensitive, and apply some good quality flux (you can never have too much flux). Pick up one of the cheap flux pens (also from ebay) and use that if you don't already have some suitable flux. 

Place the piezo element on some bluetac or rodico.

Tin the end of the wires you are using, and cut the tinned end to about 1 to 1.5mm in length, not any longer.  

Hold the wire in place with another bit of bluetac (not attached to the disk though), and move it till it sits exactly where you want it.

Hold the soldering iron on the wire, just long enough to transfer in enough heat to melt the pre-tinned wire, the pre-applied flux and the solder paste, or solder to get them to melt.

Remove the iron, and let the solder re-solidify. The whole operation should take perhaps a couple of seconds.

Clean any flux residue off with isopropanol or surgical spirit and an old toothbrush.

Job done.

As you might have gathered I've played this game a few times before.

https://stm32duino.com/viewtopic.php?f=3&t=1329&p=17153&hilit=piezo+elements#p17153

BTW the piezo elements also are available pre-wired, so you can save yourself the challenge, by spending a few cents more. Finally, don't pay more than a few cents for the elements. They are cheap as chips on ebay if you search carefully, as are electret, ceramic and magnetic microphone elements.

Edited by AndyHull

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One more observation. Why solder the brass pin to the piezo? If all we are looking for is a mechanical (acoustic) rather than electrical connection, then epoxy or cynoacrylate might be more appropriate (and easier to fabricate).

Perhaps I'll stop talking the talk, and actually walk the walk when I get back from holiday.

A custom watch holder and transducer looks like an interesting project, and a good excuse to play with my underused 3d printer to boot.

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I wonder if these could be pressed in to use as a preamp. They ticks all the right boxes. Frequency filtering (bass and treble), cheap, battery powered, cheap, plated through hole construction, so easy to build.. and err.. cheap, so if you blow it up, it doesn't matter.
 

Preamp.jpg.e22bfd22a80e65ed50041b79495af58e.jpg

You would need a suitable >12V AC supply, a wall wart for an old stand alone analog modem perhaps, (or with a little effort, you could easily modify it to work on a couple of 9V batteries).

 

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An even simpler version.

At that price, you can afford to make a few mistakes. :D

Better still, that design only needs a single supply (but you do loose the balance/treble/bass controls).

You could always mess with the NE5532 amplifier filtering by substituting some of the smd components with wires and variable resistors if you feel the need.

Edited by AndyHull

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I bought this one.

I know it needs a dual supply, but I think it was this that sold it to me..

Quote

Special Note:Since this is a multiple amplification module,Which is a whole multiple of amplification,if in your sourse noise is large,the noise also followd amplification,so you must make sure your sourse is  not noisy

With directions as succinct and precise as those, what could possibly go wrong. When the slow boat brings it from the far east, I'll keep you posted.

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Hi All ... I just wanted to let you know that I've just released Watch-O-Scope 1.3, with the following improvements and new features:

Built-in volume boost, adjustable via scope and manual adjustment modes, requiring less external amplification.

Long term test improvements:

  • Ignore extreme outliers (±4σ) for better immunity to non-timekeeping noises (e.g. the date wheel clicking over at midnight, doors slamming, cars crashing outside).
  • Clip graphs to three standard deviations (±3σ).
  • Highlight one standard deviation (±σ).

Support for manually selected beat rates all the way down to 300 bph.

Report weights for standard positions are remembered and become the defaults for subsequent reports.

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3 hours ago, mecedo said:

Can someone advise me if smaller piezo (15.5mm) will be better than 27mm? Will smaller be more sensitive?

I find a smaller piezo to be a little better.

Here I've attached a .zip file containing two comparisons between 27mm and 12mm piezos from an 18000 bph and 21600 bph movement.

Hope that helps!

27mm_vs_12mm_Piezo.zip

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