Jump to content

Recommended Posts

Have you looked at contact mics?

https://www.gear4music.com/PA-DJ-and-Lighting/Korg-CM-200-Clip-On-Contact-Microphone-Black-and-Red/U11?origin=product-ads&utm_campaign=PLA+Shop+-+Korg&utm_medium=vertical_search&network=google&adgroup=1+-+Product+Level+-+Korg&merchant_id=1279443&product_id=38917d1&product_country=GB&product_partition_id=93699991999&gclid=EAIaIQobChMIyLfl36Cc2gIVCp3tCh0OPQgXEAQYAyABEgKh1PD_BwE

 

As for the piezo disk, could you epoxy a brass pin to one? Crude drawing:

Yellow/green : piezo element

Red : Brass pin

Blue : epoxy (unless you could solder it?)

pickup.jpg.8240679f6561f14de880d97ba86c53bd.jpg

 

You could then surround the element with foam or similar to block external sounds - only vibrations trasmitted via the pin would be picked up.

Effectively a piezo stethoscope.

 

 

Share this post


Link to post
Share on other sites

That contact mic is a piezo, and is also known to work. However, it's not very practical for working on an opened watch.

The brass pin idea is sort of what we already use, except we use a pin attached to the watch movement (more commonly referred to as the winding stem and crown). It might be worth trying to cover the piezo disk with foam though, leaving a hole for the crown to go through.

Share this post


Link to post
Share on other sites

The protruding pin idea is not entirely new. If you look at the commercial microphone that comes with watch timing machines it's basically protruding pins isolated from the base with some form of rubber and the sensor. So I have two links below to where the discussion showed pictures of pickup devices you can see the sensor is isolated with a protrusion.

Then images attached of the inside of the pickup disassembled so you can better see how it works. You will notice in my picture though you'll have to refer to the links below as to how the sensor attaches as mine is currently missing. I didn't use enough epoxy and it fell off. So the sensor is inside a metal container grounded and a wire goes to the protruding part so it is also grounded as otherwise it's isolated with the rubber.

https://www.watchrepairtalk.com/topic/3002-d-i-y-watch-timing-machine/?page=21

 


https://www.watchrepairtalk.com/topic/3002-d-i-y-watch-timing-machine/?page=6

 

pin-5.JPG

pin-4.JPG

pin-3.JPG

pin-2.JPG

pin-1.JPG

Share this post


Link to post
Share on other sites
1 hour ago, svorkoetter said:

The brass pin idea is sort of what we already use, except we use a pin attached to the watch movement (more commonly referred to as the winding stem and crown).

Someone said the problem was isolating external sounds and I'm assuming that statement was correct.

So if you put your own pin on the transducer and insulate the transducer leaving your pin as the only conduit for vibration to reach said transducer you've effectively removed almost all background noise. That way the only thing picked up will be what is transmitted via the pin and pins don't pick up air vibrations that well. The assuming your stand is isolated from the surface it's on you should get a nice clean signal. Sure you can use the crown, but you can't isolate the rest of the transducer properly (unless you cover the lot in expansing foam).

 

Share this post


Link to post
Share on other sites
11 minutes ago, p2n said:

Someone said the problem was isolating external sounds and I'm assuming that statement was correct.

So if you put your own pin on the transducer and insulate the transducer leaving your pin as the only conduit for vibration to reach said transducer you've effectively removed almost all background noise. That way the only thing picked up will be what is transmitted via the pin and pins don't pick up air vibrations that well. The assuming your stand is isolated from the surface it's on you should get a nice clean signal. Sure you can use the crown, but you can't isolate the rest of the transducer properly (unless you cover the lot in expansing foam).

 

In fact, the piezo electric disk captures almost nothing of "normal" noise. Only the vibrations by contact. You have to experiment with an electric piezo disk first. Your questions will be answered when you do the test. In fact, I consider that the device should be better called a vibration sensor than a microphone.

 

Share this post


Link to post
Share on other sites
4 hours ago, guidovelasquez said:

Another idea that I have not been able to prove due to our limited access to technology is a piezoelectric "bimorf" sensor. According to the specifications it is much more sensitive than a piezo electric disk, and I can see that it is less prone to pick up the noise from the 60 or 50 Hz electrical network. This is it. I would like if somebody can verify it, that we share here the resusltados, building a microphone from this device.   https://uk.rs-online.com/web/p/vibration-sensors/0285784/

The pricing for this is interesting you get a single price but you have to order five. Then the last time we discussed these they weren't available in the US then their US distributor showed they could get them by special order and yes you had to buy five of them. Now it looks like the price has gone Up a little bit but you can purchase a single one.

https://www.alliedelec.com/rs-pro-285784/70637796/

 

 

Share this post


Link to post
Share on other sites

I was thinking I've seen the inside of the Chinese microphone someplace so I found the image. You notice I circled the sensor. It's not visible but on the other side of the circuit board is a op amp amplifier circuit. Then I'm not going to disassemble the witschi microphone I have I was tempted but it's too expensive to take apart even for a good cause. But I got two pictures and the sensor isn't that far away. It is shielded with metal surrounding most of it. It's the white bar firmly attached in the middle cushioned on the ends. If you look carefully there's actually a wire soldered on the middle.

Then I suspect because the size and if you look carefully at the witschi you can see a line running down the middle. If you read the spec sheet for the bimorph element it indicates that it's two layers.

Share this post


Link to post
Share on other sites

 

9 hours ago, JohnR725 said:

I was thinking I've seen the inside of the Chinese microphone someplace so I found the image. You notice I circled the sensor. It's not visible but on the other side of the circuit board is a op amp amplifier circuit. Then I'm not going to disassemble the witschi microphone I have I was tempted but it's too expensive to take apart even for a good cause. But I got two pictures and the sensor isn't that far away. It is shielded with metal surrounding most of it. It's the white bar firmly attached in the middle cushioned on the ends. If you look carefully there's actually a wire soldered on the middle.

Then I suspect because the size and if you look carefully at the witschi you can see a line running down the middle. If you read the spec sheet for the bimorph element it indicates that it's two layers.

Thanks for the information, I just do not see the pictures. And I would like to see the images of the Wistchi

Share this post


Link to post
Share on other sites
3 hours ago, guidovelasquez said:

Thanks for the information, I just do not see the pictures. And I would like to see the images of the Wistchi

There a new invisible pictures you need special glasses to see them which I forgot to include in the email. Or perhaps I shouldn't do these things late at night.

pin-8.JPG

pin-7.JPG

pin-6.JPG

Share this post


Link to post
Share on other sites

I agree the piece enclosed in the red circle is the bimorph sensor with its two copper wires.

In this photograph of the microphone that I use also enclosed in a blue5ac3f65e429f0_MicElmaMiniTest(3).thumb.JPG.c839dccd3bb1d007d74a95ae1255d79b.JPG circle, it looks bigger, but once again I want to indicate that it is a microphone with about 40 years.

 

Share this post


Link to post
Share on other sites

The red circled rectangle in the picture above, looks like a flexible Piezo Vibration Sensor, such as:

https://www.sparkfun.com/products/9196

Here is the technical manual:

 https://www.sparkfun.com/datasheets/Sensors/Flex/MSI-techman.pdf

I glanced through all 86 pages, no sample amplifier; but maybe its not necessary?

Here is a sample Arduino circuit:

https://learn.sparkfun.com/tutorials/piezo-vibration-sensor-hookup-guide

Here is how to build a knock circuit:

http://www.learningaboutelectronics.com/Articles/Piezo-knock-sensor-circuit.php

 

Now that I see that, it makes sense. We don't want a microphone for all the reasons related in this thread. We want a knock sensor that feels vibrations and responds to them.

Edited by cuevobat

Share this post


Link to post
Share on other sites

Thanks for the contribution CuevoBat. Very good. I think one of the conditions for the efficiency of the sensor in question that serves to capture the sound of a clock, is that the sensor itself does not come into contact with anything but the part that touches the clock.5ac3fdb1546ad_Sensorymoneda.jpg.306ad4d6a69ea2d6ce87d76f5d1bdc89.jpg

Share this post


Link to post
Share on other sites

Here is my Heath-Robison mk 1 watch holder mic assembly. Fully adjustable to any position.

Using:

  • Lapel mic
  • Camera ball mount
  • Elastic band
  • Polystyrene pizza base
  • Chair foam
  • Bit of old watch mainspring

 

But first - here is a trace obtained from this. (Remember no pre-amp, just a lapel mic)

scope2.PNG.7e41b39de06b7c223a148e34e5f36c6f.PNG

 

So here we are:

Components.thumb.jpg.b26db894b81942cb63d03b334b5ca982.jpg

 

P4070014.thumb.JPG.39691b43925bc1d019e8b0bd07be226c.JPG

 

P4070015.thumb.JPG.ef6c4a073c38d7f97f44fb862172cf14.JPG

 

P4070016.thumb.JPG.84e300dfbbcd4e942d4c4a43c7e9e385.JPG

And the chair foam provides vibration isolation.

:)

For the mark two I'm going to replace the gorilla pod with a proper stand with foam feet. Swap the elastic band for a sprung retainer of some form and use a more expensive pizza base - maybe Hawaiian or pepperoni.

 

P4070013.JPG

P4070018.JPG

Share this post


Link to post
Share on other sites

Very good. You see good results. Progressively you can improve any system to make efficient and safe. The trace is very good taking into account that there is no pre-amplification. And with that level of signal I have seen that WOS, works perfectly. I would like you to share a sound file to be able to listen.

Share this post


Link to post
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.   Paste as plain text instead

  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.

Loading...

×
×
  • Create New...