Jump to content

Recommended Posts

@JohnR725 and @RicardoG John kindly posted pictures about old sensors on: Page 6

sensor_1.jpg.0377908d546fcc2474bae76b26cb895b.jpg

sensor_2.jpg.e40fa31d9965a722a5b7591209a09a1f.jpg

What are these sensors? Are these piezo crystals? Or what are they? Is it possible to buy new? I assume it is not thats why we are looking for alternatives?

And one more sentence which grabbed my attention but I dont understand: 

@JohnR725 could you please help me with this, what does it mean? This sentence was also posted along with the pics on page 6:

"Then confusing wires because there are coils on the other side not visible for picking up balance wheel electric watches."

Link to comment
Share on other sites

@jamez361 What kind of glue have you used to attach the BM15015-06HC bimorph in this post: bimorph

Does it matter as where do you attach the sensor to the metal base alongside its length?

Its datasheet says:

Output @ 5mm clamp from lead-end (cantilever action) vibration @ 10μm P-P= 4V P-P

So 5mm from the lead-end, would the reading change drastically if you would move your clamp alongside the sensor? Who knows hahh? 

It's also moisture resistant. No evaporating sensor!!! ?

RS Pro Datasheet.pdf

Edited by luiazazrambo
Link to comment
Share on other sites

Good job @luiazazrambo you have done your homework. I see that you have thoroughly read the blog.
I will try to explain as best I can.
The bimorph sensor is a piezo electric and is not sensitive to humidity, not to the degree of the old salt-based crystals used by the timegraphers of the 40s 50s 60s 70s.
But from my experience, they are not that sensitive.
The glue: It can be a good quality epoxy resin. The idea is that it solidifies very well, as it is the passage of vibratory waves towards the crystal.

877880040_MicElmaMiniTest(1).thumb.JPG.c62e895cb79e3ee95014f2e71ce3d404.JPG
About the coils. Some stands for examining watches, (not the case of yours) had a switch to leave the vibration sensor and use a magnetic sensor. Some watches, very few in the 1970s, used a magnetic balance. For this type of watches the magnetic sensor was needed.

910680759_MicElmaMiniTesttags(5).thumb.jpg.dcc2314b224729ccca110fcf6ab8992a.jpg

About the bimorph sensor, Stefan sent some to Ryder in California. And Ryder shared one with me here in Guatemala for testing. It is not as sensitive as we expected. But what I can tell you is that what you should do with your microphone stand is to place a piezoelectric disc and it will work wonderfully for you.

Magnetic Balance.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

2 hours ago, luiazazrambo said:

Who knows hahh? 

Looking at the technical specifications you get two things the word cantilever which I have a Wikipedia link below. I basically think of a diving board type mounting the sensor has to stick out so it can vibrate. Then the wording of the mounting is interesting @ 5 mm clamp from end cantilever action. So I think there's saying you can mount it anywhere within the first 5 mm from the leads to get a nice diving board affect. 

https://en.wikipedia.org/wiki/Cantilever

sensor technical specifications.JPG

  • Thanks 1
Link to comment
Share on other sites

I think I am saved, woah! ? Not to worry, not even for a second! ?

make-a-mic-from-baking-soda-cream-of-tartar

How to make Rochelle salt piezoelectric crystals

How to test Rochelle salt piezoelectric crystals voltage oscilloscope

Harvesting Crystal for Piezo Microphone - Pure DIY

Homemade Crystal Mic from Chemistry

Crystal Microphone

"Early crystal microphones used Rochelle salt because of its high output, but it was sensitive to moisture and somewhat fragile."

I can confirm the fragile part at least, i placed my crytal on the window sill for photography, the wind caught it and when its landed on the carpet it broke into half. I must add that it is about 70-80 years old as far as I understand.

Edited by luiazazrambo
Link to comment
Share on other sites

8 minutes ago, JohnR725 said:

Looking at the technical specifications you get two things the word cantilever which I have a Wikipedia link below. I basically think of a diving board type mounting the sensor has to stick out so it can vibrate. Then the wording of the mounting is interesting @ 5 mm clamp from end cantilever action. So I think there's saying you can mount it anywhere within the first 5 mm from the leads to get a nice diving board affect. 

https://en.wikipedia.org/wiki/Cantilever

sensor technical specifications.JPG

Yes this sounds like right. This is what we can see on @jamez361 pictures, while on @Mark pictures the bimorph was glued to the base metal in the middle. Yes, I did my homework. ? 

Link to comment
Share on other sites

1 hour ago, guidovelasquez said:

About the bimorph sensor, Stefan sent some to Ryder in California. And Ryder shared one with me here in Guatemala for testing. It is not as sensitive as we expected.

 

Hi @guidovelasquez,

if our assumption is correct, then your way of using the bimorph is incorrect. You glued down two third of the bimorph. This is not a criticism not even sure if this is wrong, just trying to figure out how to use it correctly. 

From the wiki page John posted: "A cantilever is a rigid structural element that extends horizontally and is supported at only one end." 

guido.jpg.9fa6f9d52a7dc9fa6438c0fba7766769.jpg

Best regards,

Lui

Edited by luiazazrambo
  • Like 1
Link to comment
Share on other sites

2 minutes ago, guidovelasquez said:

He's right I didn't know. I will have to repeat the test with that information. Although I do not think it significantly modifies the results.

Yes, that might be the case, however it is always nice to do the experiment and see what happens. It could turn out that it would actually give you a better result. You wont know if you dont try.

2 minutes ago, guidovelasquez said:

Regarding your project, I can assure you that the best thing will be to place a glued piezoelectric disk instead of the crystal.

The reason why i want to go for the bimorph element is because both Mark and Jamez reported that they don't use a pre-amp. As far as understand piezo always require a pre-amp and I am trying to avoid that.

  • Like 1
Link to comment
Share on other sites

1 hour ago, luiazazrambo said:

bimorph was glued to the base metal in the middle

 I haven't looked at the pictures the Chinese microphone in a while but I do remember it was mounted in the center. If you look at a witschi microphone they are mounted in the center. Then on each end appears to be a small block of something soft. I assume that is so that if you drop the microphone the sensor doesn't pop off or break. They may even be there to limit the flex so don't also generate a voltage spike if you whack the thing but these are just guesses.

46 minutes ago, luiazazrambo said:

f our assumption is correct, then your way of using the bimorph is incorrect

I found a couple links for us the first one is interesting. I'm using the word interesting because it didn't exactly have what I was looking for at least in a simplistic way that I would like to have. The second link is better.

We know from the first link that impact or compression of some crystalline materials will produce a voltage. The problem is were trying to pick up something that's not generating very much of a vibration. So what you really want to do is flex your crystalline structure which will generate the compression and the voltage. But as a reminder I'm not a specialist in this field I'm making a wild guess.

If you want to get maximum flexibility or flex of your crystal mounting In a cantilever or mounting it on one corner would allow that to occur. Such as in the image which I snipped out where the crystal is mounted on one corner only. We know from the interesting wording of the instructions for the green sensor that it would ideally like to be mounted on one end if you would like the maximum signal. It probably would still work if you glued it flat providing they signal was large enough which it's not going to be in our application.

It would be nice for experiment if you would glue a new sensor on sticking it out. Unfortunately you're not going to remove the current sensor because they really don't like that kind of flexing they will break. So perhaps gluing another sensor on the work fine it gives you the option of comparing.

It would be nice if you would reposition your sensor and see if you get a better signal. Unfortunately any attempted removing it will break it. You probably just leave that sensor in place glue a new sensor on an move the wires around. I suspect you're going to get a much better signal out of it.

https://en.wikipedia.org/wiki/Piezoelectricity

https://en.wikipedia.org/wiki/Bimorph

 

 

image.png

  • Like 1
Link to comment
Share on other sites

1 minute ago, luiazazrambo said:

The reason why i want to go for the bimorph element is because both Mark and Jamez reported that they don't use a pre-amp. As far as understand piezo always require a pre-amp and I am trying to avoid that.

Unfortunately this statement is incorrect at least as far as Mark. In his video he conveniently does not show the preamp it's hiding. He's not looking for it so he doesn't see it but it's there if you go really carefully in the video you'll see it.

Then it would be nice if you could show me where the posting by Jamez Is so I can see what it has.

  • Haha 1
Link to comment
Share on other sites

32 minutes ago, JohnR725 said:

Unfortunately this statement is incorrect at least as far as Mark. In his video he conveniently does not show the preamp it's hiding. He's not looking for it so he doesn't see it but it's there if you go really carefully in the video you'll see it.

I have not seen a video in this topic. Have I missed that? (Otherwise i think i must have seen 95% of his youtube videos)

My assumption was based on his post where he said: "This just works by plugging into the sound card on my laptop or PC."

Mark's comment

 

Quote

Then it would be nice if you could show me where the posting by Jamez Is so I can see what it has.

James setup is on page 10 and actually Guido made a note that there is no pre-amp and Jamez confirmed it:

Jamez setup.

Edited by luiazazrambo
Link to comment
Share on other sites

10 minutes ago, luiazazrambo said:

James setup is on page 10 and actually Guido made a note that there is no pre-amp and Jamez confirmed it:

Jamez setup.

It looks like I'm only 50% correct. Somewhere in the universe Mark has a video showing the inside of his microphone and the circuit was hiding just not really visible and he went too fast to really show it. 

Looks like you're correct. Jamez Is not using any form of a preamp or anything else other than the pickup. But notice where he mounted the sensor? Definitely a better place to mount it then other places where you could mount it where it wouldn't flex at all.

microphone mounting.JPG

Link to comment
Share on other sites

Yes, I agree. Jamez setup seems to be correct.

As Mark sent his mic for refurbishment and later on you showed a pic how small a circuitry could be I never ruled out that there is some sort of pre-amp what is hidden. However he stated twice that there is no pre-amp. Going to look for that video now. 

Edited by luiazazrambo
Link to comment
Share on other sites

I don't know who James is. But if he explains, I can help.
I already removed the bimorph sensor from the metal part. It's in good condition. And I must take care of it because nowhere in my country do they sell. It's the one Ryder @24h shared with me.

IMG_5849.thumb.JPG.1d0dfc1a6b559e8aaccb735985e16179.JPG

There is one more thing I can assure you. THE BIMORPH SENSOR WILL NOT WORK WITHOUT A PREAMPLIFIER.
Preamp is required.
But there is a simple solution. is to add a transistor and a resistor only.

https://bit.ly/3s2W0jQ

https://bit.ly/2NzhqGn

Edited by guidovelasquez
add link
  • Like 1
Link to comment
Share on other sites

Yes I have seen that solution. I am willing to take any option but the pre-amp. ?

You might be right about that this bimorph needs a pre-amp, but I am still not convinced just yet. Its data sheet states that it will generate a 4V P-P wave if you vibrate the end by 10um. Of coruse we do not know what kind of force would reach this sensor coming from the watch vibration.

bimorph_ouput.jpg.83622a05a0d6689228f9db496aae45fb.jpg

I tried to find something similar for the piezos but only found studies how to harvest energy by walking on them, like this: Walking on piezos.

Edited by luiazazrambo
Link to comment
Share on other sites

22 minutes ago, luiazazrambo said:

bimorph needs a pre-amp

I assume we covered it way back somewhere in the million pages of this discussion. Computers are expecting capacitive microphones. The Impedance is different then these sensors. To get the maximum transfer you need to match the Impedance. You can get sloppy don't have to match I think if you put enough signal that it's not going to matter. Then there is the thing that bothers me that I don't see on the spec sheet which is capacitive microphones have DC voltage applied to them and? It's not on the spec sheet I don't see where it says DC voltages Are bad but I was just wondering if that's an issue with these?

Then there's the other problem computer microphone inputs are not all identical. We've covered that somewhere in the past. This means whatever you have may worked perfect for you but it may not work for somebody else. One of the solutions to this is to go to a USB sound device with microphone input. But even though is can vary you can have identical units and internally they're totally different and the noise level can be dramatically different. Unfortunately were not dealing with an exact science here were going to get variations but the overall concept of all of this does work.

 

 

 

Link to comment
Share on other sites

Here is an example of a recording with a piezo disk and a transistor. There is no preamp circuit (although actually the transistor + resistor is). It is sufficient for most of the watches that you will examine.
And also the screenshot of wos. Note that none of the preamp has been added.20 seg. Transistor Clean.wav

1997277295_mictransistorpiezo.thumb.JPG.b7fcbce448673f1eb07d9e4d76e0725f.JPG

  • Thanks 1
Link to comment
Share on other sites

Amplified from 2:10 Repairing Swatches.Timing Software.Loose Crown.Tools needed to start Watch Repair

Amplified from 3:42: A Seiko 4L25 with a Strange Sound - Timegrapher to the rescue

These videos were published two years later than the pics which were posted here in 2015 though, and I could not find a video where specifically the microphone was featured.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...