# watch timing microphone



## tpd80 (Jun 28, 2011)

I found some software that might suffice for a PC based timing machine.

I'm wondering if anyone can recommend a good Mic for the PC that will work? Or at least maybe provide some information like what to look for that will help me find a decent mic to use?

Thanks


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## The Guvnah (Nov 9, 2011)

Not an audio engineer (more muso) nor a watchmaker but I'd look for the highest sensitivity possible I'd guess. You'd want it to be strongly unidirectional and after that its a matter of good signal conditioning, noise rejection and good clean pre-amplification before being sent into the audio card which is what your software ultimately will be listening to.

Personally, and speaking with my electrical/electronical hat on, if I was undertaking this I'd consider placing the watch on a non resonant surface and using a PZM (pressure Zone Mic) or piezo transducer attached or otherwise accoustically coupled to the watch caseback. Modern transducers should have no problems picking up the tick of a mechanical watch in fact I bet I could record my watch's tick just by holding it against my phone. In fact they're so good that there may well be a requirement for some pre sound card filtering to supress all the extraneous creaks and boings which could trigger a false count from the software!

With either approach there is the question of latency in the audio-digital conversion process which can be from a couple to tens of milliseconds depending on how heavily the processor is being worked. In and of itself the latency between the transducer sending an audio pulse and the sound card receiving and converting it is not important as what you're measuring is a relative quantity, the crucial thing is that any latencies or propogation delays are reliably constant. If you've got other programs kicking their way onto the bus and demanding attention then it may have repurcussions. I'm guessing also that the software help guide would mention this. What are the intervals being timed btw? Again I'll take a guess and say 250ms between ticks/pulses so a variation in latency of even 5ms could render the whole excercise invalid. How is it done professionally?


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## tony1951 (Jan 11, 2012)

I haven't done this, but I was reading about it and from what I have gathered microphones are no good at all, no matter how directional because they pick up loads of sound from outside the watch. 

What you require if you don't buy a purpose made (expensive) device, is an acoustic pick up of the kind used to 'electrify' guitars or mandolins. I am going to do this with the software called Biburo which is free. All the threads I have read on this stress that ordinary microphones are designed to be sensitive to airborne sound which is the last thing you want. An acoustic pick up is designed to detect vibrations in an object (soundboard) and can be clamped onto a watch case. 

You may find that you also need some kind of pre-amp in order to match the input requirements of your sound card. I tried a cheapo peizo electric element from a crystal earpiece. In theory it would have been fine, but the signal level produced by the watch was far too low and was just in the noise.

I believe you can buy clip on transducers for guitar and mandolin 'electrification' for not much money. I've seen them on ebay and Amazon for about £10. When I get around to this, that's the route I will try first, but they come with 1/4 inch jacks so some fiddling and soldering will be required. If you can't knock up a simple audio preamp, you can probably cobble together a pre amp from an old powered PC speaker system. Connect the speaker input system to your transducer / pick up and the speaker output to the soundcard input. Start with the volume turned right down and gradually turn it up until you reach the required threshold for detecting the watch escape sounds.

Good luck and of course - all at your own risk. I doubt you'l damage your soundcard input, but have a care on its input levels.


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## The Guvnah (Nov 9, 2011)

Just had a fish round my parts bins and plucked out a £1:50 piezo transducer, hooked it via a breadboard direct into the input of my practice amp. I put a dot of tape over its solder connections so that the case wouldn't short the output. I placed an old mechanical Timex with a moderately loud tick gently on the transducer. I rolled off all the bass and middle, and turned all amp volumes to ZERO!
I switched on and gently brought up the pre-amp and master vol. controls and... bingo! clear as a bell! The amp's master vol is at 4 and the pre-amp at 3 so there's plenty more gain to come if needed but noise and mains hum starts to intrude but it's nothing that couldn't be cleaned up with some basic signal conditioning. I've got none of that, this is about as rough and ready as you could get so listen to no-one who tells you that you'll need 2 grand's worth of Nuemann Studio condenser mics! In fact if I had one to hand I'd whack a graphic or parametric equaliser into the chain and you could probably tune in to particular parts of the escapement and train. Works a treat so if you'll give me an hour or so I'll snap a few pics and upload an audio file of the results.

T.T.F.N.

The Guv


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## tpd80 (Jun 28, 2011)

Guys this is great info.

Its going to take me awhile to digest all this stuff.

If anyone has a setup completed or could whip one up I'd be more than happy to flip them a few bucks if they want to send it too me.

PM me if so.

Thanks again everyone.


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## The Guvnah (Nov 9, 2011)

Here y' go chaps...

Here's the lash up.










The only "work" involved was stripping and tinning the ends of the transducer wires to fit the breadboard contacts better. Here's a close up of the business end, nowt special at all. If you've got any kids you'll probably find a transducer in one of their more annoying beeping digital toys, open it up and gut it out and there's your transducer, two problems solved in one hit!










Note the tape over one of the solder pads to prevent a short.

Here's some of the lads, all queuing up and dying for a go on it. Even the Aqualands which I can barely hear with my own ears came out strongly and the modded Seiko 6309 sounded particularly fantastic.










...and here's the scope trace of the audio recording...










Unfortunately it won't let me attatch the mp3 recording, sorry fellahs.

What's also interesting is the ability to visibly determine the ticks from the tocks so to speak and with some basic hum and hiss filtering and maybe some compression and gating you'd definitely have a "clockable" signal that can be delivered to your software. It depends of course on the degree of discrimination the software can apply to its input signal. I used nothing at all in the way of signal conditioning apart from the basic bass, mid, treble controls on this monkey amplifier. Housing the whole shebang in an aluminium case would shield it from the mains noise pretty well I would think and reduce that mains hum to very acceptable levels. Beware of feedback and howlround if you turn the amp gains up a tad too high, I had the amp up on the same worktop as the transducer which will aggravate it, solved by placing the watch and transducer on a folded towel to isolate it from the surface.

Oh yes, a further thought ocurrs to me. The recording software is Audacity and you can expand the trace's time axis considerably which might be a useful feature by which to gauge the regularity and duration of the beats?


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## GeneJockey (Oct 7, 2010)

I've had surprising success with just the built-in mic on my laptop. I can hang a watch over the top of the monitor, and after fiddling a bit for maximum S/N, record the ticking. I can also lay the monitor down flat and do dial up/dial down comparisons.



The Guvnah said:


> Oh yes, a further thought ocurrs to me. The recording software is Audacity and you can expand the trace's time axis considerably which might be a useful feature by which to gauge the regularity and duration of the beats?


Exactly! You can also add a 300 bpm 'click track' as a standard, and look at the symmetry of the 'tick' and 'tock'. Record for a minute, align the first reference tick with the first real tick, and if you look out at one minute, you can estimate how fast or slow the watch will run.










And you can use it to check for beat errors. The top track is the reference, the middle track is a watch that's in beat, and and the bottom is out of beat.


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## tpd80 (Jun 28, 2011)

How you apply the piezo sensor to the watch?
Do you just rest the case back on it? do you have to cover the sensor to prevent short circuits?



The Guvnah said:


> Here y' go chaps...
> 
> Here's the lash up.


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## DragonDan (Dec 22, 2009)

I like this idea, using stuff you'd already have around. While I don't have a piezo mic, I've got a few mics for my computer's inputs. I will do some experimenting this weekend.


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## GeneJockey (Oct 7, 2010)

DragonDan said:


> I like this idea, using stuff you'd already have around. While I don't have a piezo mic, I've got a few mics for my computer's inputs. I will do some experimenting this weekend.


I think I'll see what I can do with an old 'gamer mic' my kids no longer use. Holding the laptop with the monitor flat on the table, and the keyboard up in the air for a couple minutes doing dial-up/dial-down is a pain!

It should be pretty straightforward, I think. I think too many folks worry too much about noise - the watch will be the loudest thing the mic hears in a quiet room, if it's on top of it.


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## The Guvnah (Nov 9, 2011)

tpd80 said:


> How you apply the piezo sensor to the watch?
> Do you just rest the case back on it? do you have to cover the sensor to prevent short circuits?


In this instance yep, that's all I did. If doing this seriously I'd figure up a more reliable accoustic coupling, even a few wraps of a thin elastic band round the two of them would probably double the output signal strength from the piezo alone.

More likely I'd make up a spring loaded jig consisting of two opposing plates, one fixed and the other sprung to allow a watch to be interposed between them. I'd cement the back of the transducer to the static plate. As you can see from the photo they're made up on a very thin brass substrate and so it's very easy to bend it and detach the piezo element which pretty much knackers it. Then you just slip the watch and a lightly sprung moving 'jaw' applies just enough pressure to maintain intimate contact between case and transducer. A hard industrial plastic such as Delrin would be preferable to more accoustically 'absorbant' stuff like plywood, hardboard or pressed composite board like M.D.F. (medium density fibreboard in the UK) as it wouldn't dampen the sound transmission so much.
A soft metal like brass might also work but might introduce its own tones into the mix, I dunno, I'm just thinking around the periphery here.

Basically if you allow anything metallic/conductive to connect across the transducer's two output terminals the tiny millivolt signals produced at the positive (red) terminal will take the easiest route home and shoot straight across to the negative wire and back into the crystal element from which they originated thus completing their own circuit. We want that signal to travel all the way up the red wire, into the input pre-amp on the sound card, do it's work in the analogue to digital convertor section and only then can we allow it to return down the negative wire.

I just used electrical tape because I had a roll 4ft from the bench, for real, then I'd probably apply a few drops pf epoxy resin to properly seal and insulate them. Those output wires are very flimsy and easy to work harden at the point were solder meets conductor whereupon they simply drop off. Therefore...

For the Gucci' version I'd place the transducer (with the front smeared with a little vaseline) face down in a plastic project case lined with e.m.i. shielding foil, add a low noise "pre-amp on a chip", bring a 3 or 4core screened cable into the case to bring DC in for the chip and take the amplified signal out. I'd do a test of it and if all's well then I'd seal the whole thing into a solid block with half a pound or so of two-pack epoxy 'potting compond'.
When hardened off I'd carefully machine off the bottom of the case to expose the transducer's non-stick and hopefully resin free face and there y' have it. Seemples!


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## The Guvnah (Nov 9, 2011)

DragonDan said:


> I like this idea, using stuff you'd already have around. While I don't have a piezo mic, I've got a few mics for my computer's inputs. I will do some experimenting this weekend.


Worth a go but mine was hopeless. So much accoustic energy is dissipated in its traverse through even a centimetre or so of air between case and microphone. It's the transitions from one material and into another that are responsible for a lot of the attenuation, by using a contact mic you immediately remove one material-air-material interface from the chain = less energy lost twixt movement and recording element = bigger output signal.

My guess is that laptops with mics built into the top corners of the screen panel might work better because the whole panel acts like a resonator/amplifier for the movement's ticking.


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## spiro13 (Dec 15, 2010)

The Guvnah - Do you have any problems with line noise? I have been trying this with Biburo for a while but no matter what I try I can't eliminate the line noise. Is there a filter or will shielded cables help?

Thanks

Tony


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## The Guvnah (Nov 9, 2011)

GeneJockey said:


> Exactly! You can also add a 300 bpm 'click track' as a standard, and look at the symmetry of the 'tick' and 'tock'. Record for a minute, align the first reference tick with the first real tick, and if you look out at one minute, you can estimate how fast or slow the watch will run.


Aha, nice one.



GeneJockey said:


> And you can use it to check for beat errors. The top track is the reference, the middle track is a watch that's in beat, and and the bottom is out of beat.


1x pic = 1000wrds... and just from those traces I now have a much better visualisation of what "beat error" actually is, thanks for that one Gene.


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## The Guvnah (Nov 9, 2011)

spiro13 said:


> The Guvnah - Do you have any problems with line noise?


Well the bottom line is the miniscule signal levels a piezo electric transducer puts out. Any varying electrostatic or electromagnetic sources near to an unshielded cable will induce a current into that cable's conductor/s. Sometimes the superimposed voltage is of sufficient magnitude to completely swamp the signal that the conductor is supposed to be carrying. Sometimes the induced voltages are very transient such as when an appliance is switched ON/OFF producing 'spikes' of radio energy from the tiny (but still powerful) electric arc that occurs across opening switch contacts that are carrying a heavy load current. In that case the signal won't be swamped as such but the spike voltage might be misinterpreted by the downstream circuit.
For instance; if that signal is carrying say the signal from a temperature sensor controlling an industrial baking oven or even a domestic heating system then the receiving circuit will see that temporary high voltage and think "oh my god this oven/living room is at 9,000 degC! and trigger its shutdown routine, just because someone turned off a motor.
Shielded cable contains an outer sheath of either braided fine copper wire or an aluminised conductive foil wrapping which surrounds all of the cores within the cable. When terminating such a cable the shield braiding or foil has a connection made to it to the circuit's ground/neg/earth/0v line. The function of the sheath is to intercept any stray voltage inducing forces before they reach the signal carrying conductors beneath it. Any RF or magnetic field will dissipate all its energy into the shielding inducing a current which is then led immediately to earth/neg/0v completely bypassing the working part of the cct.

It's a complicated business and when you're dealing with such tiny signal voltages in the order of millivolts then mains voltage induced 60/60Hz hum should be considered omnipresent in the domestic environment and shielded cables are de rigeur. My lash up was just that, a lash up. I wouldn't expect to feed that filthy raw signal into a software in that condition and expect it to clock cleanly. Maybe the program contains its own pre count filtering, gating, limiting and compression algorithms or plugins to help clean up the input but by that time it's too late as it's already in the sound card and i reckon post soundcard processing is just going to add to the cumulative processing and propogation delays or variations. I think that in this case old fashioned outboard analogue signal conditioning is the way to go here as software based, compressors, graphic eq's and such will always introduce extra latency and processor load/drift.



spiro13 said:


> I have been trying this with Biburo for a while but no matter what I try I can't eliminate the line noise. Is there a filter or will shielded cables help?
> 
> Thanks
> 
> Tony


Your welcome Tony,

Not sure what Biburo is actually??? As above really, using unshielded cable is asking for hum and noise problems. Bin it and get some GOOD QUALITY audio grade cable. Also don't rely on twisted connections, if you don't know how to solder, blow $25 bucks on a decent 15 watt Antex soldering iron and the little widgets that go with soldering work and teach yourself in an afternoon. An unsoldered connection can easily lose 3dB of level over a soldered one which equates to half your signal strength! This will help a lot but if the transducer is hanging out in the 'unshielded electromagnetic breeze' even shielded cabling won't eliminate the source of the trouble, consider mounting it all in a conductive enclosure... biscuit tin connected to the cct's 0v rail... that'd do.

There's probably a lot of stuff in your house that's radiating energy besides the mains it's just that we tend to focus on mains hum only because it is so ubiquitous and is within the range of human hearing but electronic kit can put out RFI and EMI at all sorts of frequencies way above audio range so even though you might not be hearing any interference that doesn't mean there isn't any. Piezos can output frequencies up to hundreds of kHz which your ears won't hear but an unshielded high frequency clocking circuit certainly will.


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## The Guvnah (Nov 9, 2011)

tony1951 said:


> In theory it would have been fine, but the signal level produced by the watch was far too low and was just in the noise.


If I'm wearing a quartz then I often have to take it off with some of my guitars otherwise the pickups send a hefty 1Hz clunk into the speakers as it detects the timing pulse from the watch! It's a handy reminder to not be such a klutz and risk banging up the laquer and to take my belt off as well so as not to scratch the backs.


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## EmJot (Feb 2, 2012)

The word “timing” in your thread title suggest, that you want to use your computer to time your watch thus be able to adjust it. It will not be very accurate. Just consider basic conversion from analog signal from microphone to digital data that can be use by PC. It is done at sound card at 44K times a second. Assuming your watch is 4 bps, that is two cycles per second, the conversion alone will give you an error of 3.9 seconds a day. Additional error will be from your computer timer. My PC is some 8 seconds a day off. It appears to be keeping good time but only because it is synchronized often. But for timing your watch it would be useless. To use your PC for timing you need to provide it with already formatted digital data. Then PC can visualize ticking, do all calculations, suggest adjustment and whatever else is needed. To get digitalized data you will need dedicated device that will format analog signal from microphone, as suggested here, convert it to digital at some 1M times a second with a time base for conversion being stable at least 10-6. These are pretty high technical requirements. Could be interesting electronic project thou. Professional watchmakers use devices that are quite expensive.
Michael


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## tpd80 (Jun 28, 2011)

THe idea was to use my PC's sound card. I can set it from 44khz samples per second to 192000hz on my LINE but not my MIC.

Hopefully thats true and that should help with more accurate samples.

My current method of regulating my watch is to tweek the screw and wait a few days and compare it to time.gov. Even if my PC is off im sure it'll be better than my current system.


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## tpd80 (Jun 28, 2011)

Guvnah;

Would something like this make a good amp? if it was used right at the sensor?

Low Voltage Audio Mono Amplifier Module, NJM386D,LM386 | eBay


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## Andrew McGregor (Dec 27, 2011)

EmJot said:


> The word "timing" in your thread title suggest, that you want to use your computer to time your watch thus be able to adjust it. It will not be very accurate. Just consider basic conversion from analog signal from microphone to digital data that can be use by PC. It is done at sound card at 44K times a second. Assuming your watch is 4 bps, that is two cycles per second, the conversion alone will give you an error of 3.9 seconds a day. Additional error will be from your computer timer. My PC is some 8 seconds a day off. It appears to be keeping good time but only because it is synchronized often. But for timing your watch it would be useless. To use your PC for timing you need to provide it with already formatted digital data. Then PC can visualize ticking, do all calculations, suggest adjustment and whatever else is needed. To get digitalized data you will need dedicated device that will format analog signal from microphone, as suggested here, convert it to digital at some 1M times a second with a time base for conversion being stable at least 10-6. These are pretty high technical requirements. Could be interesting electronic project thou. Professional watchmakers use devices that are quite expensive.
> Michael


So, if you use NTP, on a machine that is running Linux or MacOS (because Windows does not do NTP right), you can use the NTP-corrected timebase to measure the sound card's audio clock rate, get that nailed down, and then get a very good measure of the watch's beat.

The point is that, while there are indeed errors there, computer clocks are very consistent. The errors are not random, and you can (with a bit of work, most of which can be automated) calibrate them out.

As for the limited sample rate, that's about interpolation. Many PC sound cards will run at 192 kHz anyway, but even then you don't have to measure only to sample precision. Instead you can average over many intervals, and autocorrelate the ticks against each other to sub-sample precision.

A halfway decent bit of watch-timing software will do all of this. Maybe it doesn't exist, but I wouldn't bet against it.


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## The Guvnah (Nov 9, 2011)

Excellent stuff there from EmJot and Andy McG.



tpd80 said:


> Guvnah;
> 
> Would something like this make a good amp? if it was used right at the sensor?
> 
> Low Voltage Audio Mono Amplifier Module, NJM386D,LM386 | eBay


I'm trying to recall electronic principles lectures from 20+ years ago here lol! The little preamp module on the Bay is not what you'd call hi-fi but that's not what you're after. You just want to count the pulses not spectrally analyse them in minute detail.
My lash up worked (...ish) despite paying no regard to the phenomena of impedance matching and a good many other factors. The mismatch between the electrical impedance of the sending device and the input impedance of the receiving circuit leads to several side effects such as severe loss of signal power/strength and attenuation of frequencies. Moving coil microphone elements and guitar pickups are generally of low impedance (600 ohms is typical) and so guitar amps are designed to match the impedance of the kind of devices the manufacturer expects to be connected to them.
Fortunately the distortion of frequencies is of little import to what you're intending to do, you just want to count the 'blips' not produce library recordings of movements. The loss of signal and eleimination of extraneous electrical noise are what we need here.

A quick read of the specs reveals that the input impedance of the chip is healthily high at 10 kOhms so I reckon you'll have no problems interfacing a piezo to the front end of that pre-amp module and getting a useable signal out of it.

There's a switchable gain between 26dB and 46dB available via a removable jumper link to the left of the chip which is useful but you could probably modify it and bring that facility out to a ptoentiometer for fully variable control of the gain which could help in achieving the optimum balance between getting a useful signal and avoiding hum. The proviso is that it's housed in a shielded case and uses shielded cables throughout. If I'd had one knocking about in the parts drawer I would certainly have hooked it up and expected a big improvement over a 'raw' connection into the amp.
The only control I had over the sound card's input gain was to check the "MICROPHONE BOOST" tick box in Windows. For 8 bucks? yeah I'd go for it.


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## The Guvnah (Nov 9, 2011)

tpd80 said:


> I found some software that might suffice for a PC based timing machine.


For the sake of completeness, which software is it?


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## tpd80 (Jun 28, 2011)

I found 2 packages.

One wont run on my win7 so ill have to try it on XP when i get a chance. Its a free trial which costs 20$ i believe to register it. The installer is named "wtm207.exe". A google search should locate it i dont have the original URL that i found it on.

The one i have working is free. Its a little buggy if you mess with the settings while its running but it seems like it'll do the trick. Its called "WatchMaster". Again i dont have the original URL but if you google for "wm2026.zip" you should be able to find it.

I found these just by digging through fourms and clicking on every link i could find.

If anyone has any other software packages that are good please let me know.

Im also thinking about reading what exact metrics are needed and writing up my own software package if these dont work well enough but my signal generator is good.



The Guvnah said:


> For the sake of completeness, which software is it?


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## tpd80 (Jun 28, 2011)

The Guvnah said:


> There's a switchable gain between 26dB and 46dB available via a removable jumper link to the left of the chip which is useful but you could probably modify it and bring that facility out to a ptoentiometer for fully variable control of the gain which could help in achieving the optimum balance between getting a useful signal and avoiding hum. The proviso is that it's housed in a shielded case and uses shielded cables throughout. If I'd had one knocking about in the parts drawer I would certainly have hooked it up and expected a big improvement over a 'raw' connection into the amp.
> The only control I had over the sound card's input gain was to check the "MICROPHONE BOOST" tick box in Windows. For 8 bucks? yeah I'd go for it.


Thanks for the advice. I purchased one and its already been shipped. Ill be able to give some results in a week or two.

I noticed the jumper for 26dB and 46dB. I figured the 26dB setting would be enough for what I need it to do. You mention adding a ptoentiometer to control gain. Whats the difference between contorling the gain using that or the output using the privided dial? I guess im asking the difference between gain and output voltage.

For a shielded case, i see many nice ones made of aluminum on ebay (search 'aluminum project box') for about 5-10$. Would aluminum box be a good shield? Would i also have to connect the "shield" portion of my sheilded cable to the aluminum of the box to complete the ground?


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## The Guvnah (Nov 9, 2011)

tpd80 said:


> Thanks for the advice. I purchased one and its already been shipped. Ill be able to give some results in a week or two.


I'll be there with the camping chair and bucket o' popcorn, I am as Prince Charles... all ears!



tpd80 said:


> I noticed the jumper for 26dB and 46dB. I figured the 26dB setting would be enough for what I need it to do.


Could well be, gotta try it and see really. The only 'rule' is with EVERY adjustment or change you make whack the controls down to ZERO and then bring them up gently with your hand hovering over the master volume or sound card's input jack just in case things get unstable and start self-oscillating into feedback.



tpd80 said:


> You mention adding a potentiometer to control gain. Whats the difference between controlling the gain using that or the output using the privided dial? I guess im asking the difference between gain and output voltage.


 Searching... analogies... include sub-category... metaphor...

A bit late for the detailed explanation even if I could phrase it after 3 cans of Carlsberg's finest but it's a bit like being able to re-map a car's throttle and engine response, you can make it sensitive to the slightest change in pedal pressure for track work or dial it down for easy urban driving. Having the ability to vary the fundamental gain of the amplifier (as opposed to just the volume control) can help to tune the amplitude of the output signal against hum and extraneous noise and get optimum dynamic range, it's always going to be a trade off at this level of componentry.



tpd80 said:


> For a shielded case, i see many nice ones made of aluminum on ebay (search 'aluminum project box') for about 5-10$. Would aluminum box be a good shield? Would i also have to connect the "shield" portion of my sheilded cable to the aluminum of the box to complete the ground?


Yes and yes. Common up the cable shields to the -ve DC supply terminal on the pcb. You might possibly have to 'lift' the ground connection at the jack conector into the PC in the unlikely event of persistent "hum loop". Basically you connect the shield at one end only rather than both which breaks the hum loop. Old American made instrument valve amps had a frightening habit of fitting 'ground lift' switches to the backs of their kit to 'solve' the problem... bloody lethal devices! It cut the hum alright but left the whole amp and the connected instrument (and therefore the musician/roadie holding it) 'floating' with respect to earth potential! Just thinking of remote possibilities here you understand.

You'll also need to score a handfull of cheapo pcb spacers to stand the conductive tracks on the underside of the circuit board away from the aluminium casing otherwise it'll short out the cct board. Also a few cable entry glands to protect the flying leads as they enter the case. Bon chance!

Guv


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## tony1951 (Jan 11, 2012)

Great stuff here in this thread. And excellent advice about screening against electromagnetic noise. Unscreened leads on audio amps will easily pick up AM radio stations well enough for them to be heard on the output.

I'm wondering if this might be the way to go regarding transducers. I expect it is a piezo electric pick up like Guvner and I have used.

Clip On Microphone / Pickup for Guitars, violin, mandolin etc: Amazon.co.uk: Musical Instruments

It has the advantage that it is already soldered to a screened cable. The pity is it will terminate in a quarter inch jack. No problem if your pre amp has that fitting on the input.

It will also clip onto the watch in a near perfect arrangement.








For the non - soldering beginner, you can also buy adaptor plugs quite cheaply that would convert the 1/4 inch jack size to smaller ones for soundcard inputs etc, though I suspect the input level from the transducer would be too low for direct connection to the soundcard input.


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## Andrew McGregor (Dec 27, 2011)

That's exactly what you want. For another $40 or so, you can probably find a USB sound card with a quarter inch adaptor that should have enough gain. Or if you want, something like my Alesis io2 will take that directly and has a ton of gain with full adjustment plus 24-bit 192kHz input and ridiculously low noise levels, for about $80. Bonus is, it's also a fantastic headphone output for listening to music (and recording it, for that matter, which is what it was built for).


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## tpd80 (Jun 28, 2011)

I think ill just wire it upto a 9v battery, that way its less wires entering the box and possibly less noise.

Also thinking about just using a plastic project box now and lining the inside with foil. Might cause less head aches then having all conductive aluminum on the outside.

So the shielded audio cables shield wire will connect to the foil shielding inside and the foil should connect to the (-) terminal on the battery (since im not using a power supply)? Im not sure what you mean by "lifting ground".

I took a few electrical engineering classes in university but I haven't practiced this stuff since i graduated.



The Guvnah said:


> Yes and yes. Common up the cable shields to the -ve DC supply terminal on the pcb. You might possibly have to 'lift' the ground connection at the jack conector into the PC in the unlikely event of persistent "hum loop". Basically you connect the shield at one end only rather than both which breaks the hum loop. Old American made instrument valve amps had a frightening habit of fitting 'ground lift' switches to the backs of their kit to 'solve' the problem... bloody lethal devices! It cut the hum alright but left the whole amp and the connected instrument (and therefore the musician/roadie holding it) 'floating' with respect to earth potential! Just thinking of remote possibilities here you understand
> Guv


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## tony1951 (Jan 11, 2012)

Andrew McGregor said:


> That's exactly what you want. For another $40 or so, you can probably find a USB sound card with a quarter inch adaptor that should have enough gain.


Or for $1.25 you can buy one of these from Amazon.








You'd want a mono one though since the guitar / mandolin pickup will be a mono jack.The mono ones can be had for a dollar.


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## tony1951 (Jan 11, 2012)

tpd80 said:


> Also thinking about just using a plastic project box now and lining the inside with foil. Might cause less head aches then having all conductive aluminum on the outside.


You'd be better using a metal box. So much easier to make a reliable connection where the plugs enter, or if it is hard wired to connect the screens on the cables to the ground on the amp board. Also, if you mount the circuit board sensibly, you are far less likely to end up with short circuits when random bits of foil deform and contact parts of the amp board. The difference in price between a small metal project box and a plastic one is tiny and they are easily drilled and worked for access holes for cables or mounting plugs.


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## Andrew McGregor (Dec 27, 2011)

tpd80 said:


> Also thinking about just using a plastic project box now and lining the inside with foil. Might cause less head aches then having all conductive aluminum on the outside.


Don't use foil. Seriously, just don't. That technique works, kind of, for electric guitars where you glue it to the inside of the box, but for anything where you don't have to fit in to a weird space, it's far easier just to use a metal box. The level of pain involved in getting a decent connection to foil just isn't worth it.


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## The Guvnah (Nov 9, 2011)

tpd80 said:


> I think ill just wire it upto a 9v battery, that way its less wires entering the box and possibly less noise.


Why not mount the battery inside the case? Any Radio Shack/Maplins hobby electronics store will have a cheap little inj. moulded battery carrier for a PP3 battery and most likely it'll come with a handy sticky pad on the back, More than adequate to hold it in place and one less cable entry to make and gland off.



tpd80 said:


> Also thinking about just using a plastic project box now and lining the inside with foil. Might cause less head aches then having all conductive aluminum on the outside.


I'd echo Tony's recommendation to go with a little aluminium project case. Shielding foil ain't the cheapest stuff and is a faff to apply and ensure complete electrical continuity of the shield. With ally, it's all done for you so that'll save you maybe $8 for the tape and an hour out of your life.



tpd80 said:


> So the shielded audio cables shield wire will connect to the foil shielding inside and the foil should connect to the (-) terminal on the battery (since im not using a power supply)? Im not sure what you mean by "lifting ground".


Aye that's the idea, the shields will connect to battery *-ve*.

As for "Ground lift" switches. Cable shields (and the conductors underneath) are in fact pretty efficient receiving aerials when you think about it, they can pick up magnetic fields from any mains frequency conductor in the vicinity. Those fields will induce a corresponding current in both the braid strands and the conductors. By connecting the braid to chassis ground you offer a path of low resistance and for those induced currents which will effectively intercept and "drain" all induced currents to earth before they can impinge on the conductors we want to protect. The better the earth therefore the better it's ability to 'clamp' the shield at an unvarying 0 volts. No variation in voltage = no varying magnetic field = no induced current = no hum. However, In some circumstances where perhaps the building's fixed wiring contains high resistance earths or inadequately 'bonded' parallel earth paths the high resistance of the system earth means that the hum currents are never fully clamped to 0volts and will thus 'float' at some voltage above ground potential depending on the resistance/impedance of the earth path in question.

With me so far?

So we have this floating 50/60Hz voltage/potential now sitting there on the cable braid just looking for somewhere to flow. It can't directly flow to the supply neutral directly because it's totally insulated from it, there is no circuit or loop within which it can flow and thus induce hum currents into the signal cores therefore it can't cause audible hum. But if it can find a parallel path through the braid of another connected lead somewhere in the rig then the standing potential will cause hum current will flow, that's then re-radiated into the conductors below and you will hear an audible hum that defies all attempts to supress it.

It's that earth 'loop' that is the facilitator (but not the cause!) of mains hum and so the easy fix is to break that earth loop at some convenient (?) point and the laziest way to do that is to completely disconnect (ie 'lift') the earth/ground conductor of the affected equipment either in the back of the equipment or at the plug. Bingo no more hum but also no protection whatsoever in the event of a fault to earth within the equipment. If the amp throws a wobbler and the chassis becomes live through an internal short to chassis there is now no direct low resistance path to earth down which the fault current can safely be dissipated to the general mass of Earth (hopefully with sufficient energy to bring out the circuit fuse / breaker on its way). So it looks for the next lowest path and that is usually the instrument lead and the soles of the musician's feet! Unfortunately even the most alcohol soaked muso is rarely very conductive electrically speaking (human resistance = a few thousand ohms) so he will now find himself connected to full effects 230v AV mains conducting more than enough current to earth to stop the heart but unable to pass the 50 or so amps of current required to blow the 13A fuse in the plug. He'll be stood there dancing until somebody figures out it's not a flashback and spots what's going on.

This is generally only an issue with mains fed audio kit with their own on board transformer/P.S.U. It's the voltage difference between the building or system earth and the appliance earth that roadies used to address by disconnecting the humming 'rougue' amp's earth wire and why audio/stage equipment manufacturers recklessly used to make it even easier by factory fitting the means to kill musicians.



tpd80 said:


> I took a few electrical engineering classes in university but I haven't practiced this stuff since i graduated.


Yeah it's very easy to lose the edge if not continually sharpened. :-!


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## tpd80 (Jun 28, 2011)

wow its going to take me a few more reads to digest all that.

Yes i was planning on keeping the 9v inside the shielded case. I think its better that way then drilling more holes for power lines to enter - and noise.

I purchased an aluminum case for 8$. 

Just need to think of a nice way of mounting the piezo so its very functional but looks nice. Having the big ugly solder point on top of the disc kind of takes away from its aesthetics and makes it harder to rest a flat watch case back on it. Might layer something that's hard/stiff on top of it to place the watch on top of. Ill have a better idea once the project box is in my hands.


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## The Guvnah (Nov 9, 2011)

tpd80 said:


> wow its going to take me a few more reads to digest all that.


The trick to electrical understanding is to get the sequence of events in order with respect to voltage, current and resistance. A voltage (more correctly, a difference in potential) causes a current to flow through a resistance. It's the voltage that is the originator, if you apply that voltage across a resistance then current willl flow in direct proportion to the magnitude of that voltage (i.e. more voltage produces greater current flow through the same given resistance) The relationship between current and resistance is inverse so greater resistance results in less current given the same applied voltage.

Remember your V=I x R an' all that?


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## tpd80 (Jun 28, 2011)

Yep, i remember most of the fundamentals. I took a lot of digital logic and RLC circuit design. My hang ups are the terminology and nomenclature used im not exactly familiar with or remember.

Cant wait to get my parts so i can put all this to work.

I know beat rate, but im doing some reading on exactly what amplitude/beat error are in case my software doesn't work and i have to write something up my self.



The Guvnah said:


> Remember your V=I x R an' all that?


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## tpd80 (Jun 28, 2011)

I cut open this buzzer from radio shack and i found this piezo. I wasnt expecting 3 leads and a circuit board. What is all the extra hardware for?

Will this still work or should i look for a piezo with 2 leads and no circuit board?


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## The Guvnah (Nov 9, 2011)

Ah right, that is what's called a self oscillating type piezo and they're designed with sound generation in mind. The extra element (I think) is tapped off and fed back to the drive circuit which allows the drive circuitry to optimise its sound pressure level at the resonant frequency of the element. Basically it's designed to be a noise maker (smoke alarms that sort of thing) not a microphone.
Having said that you'd still probably get some sort of signal out of it by picking up the connections to the brass backing disc and the main element area i.e. the left-most connection in the photo.

From Radio Shack? Haven't they got a shelving peg with just single bare 2 wire elements in a poly bag? Bit of card stapled to it? $2 tops? I'll have a squint at their online catalogue if I get a spare 15.

This might be a useful read -

http://www.ryston.cz/pdf/avx/piezo.pdf

or take your pick from this lot...

http://educypedia.karadimov.info/electronics/buzzers.htm


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## tpd80 (Jun 28, 2011)

Thanks again.

I got this from radio shack ('the source' in canada). Ill check tomorrow for what you suggested. This might work well enough for tonights test with the amp that arrived.


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## The Guvnah (Nov 9, 2011)

Hmmm. Just had a quick butcher's hook at the Radio Shack Components - Buzzers, speakers and mics webpage and I'm not seeing any bare elements. There might be a member of the sales team who is sufficiently up to speed to be able to direct you to what you need but I'd guess the cheaper ones with the lower output levels will be the non self-oscillating type and the one to go for.

Ah yes; found the following pic of a piece of kit called the TimeGrapher, I'm sure it was on this forum as well... TYMC timegrapher - watch timing machine - home









What's the amplifier?


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## The Guvnah (Nov 9, 2011)

Hang on a minute - "skeletonized Vostok Amphibia" rings a bell.


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## tpd80 (Jun 28, 2011)

After wiring up the preamp it seemed to work, it diffidently amplified the signal but the signal was still very weak.

It was either my 9v was low on juice or possibly the 3 lead buzzer peizo isn't intended to work very well in reverse (vibration to signal). Apparently the 3'rd lead is an inverse of the signal so it may be canceling out much of my signal in the circuity.

I ordered a few 2 lead piezo's and ill test them out. I couldn't find any sellers local unfortunately so ill have to wait a few more days.


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## Guest (Mar 24, 2012)

Maybe stating the obvious, but 80$ here, adding 20$ there, a couple of 10$ on top of that etc...
A cheap Timegrapher set is a bit less than 200$ and works well, so if you set aside the joy of the DIY (that I can understand), what's the point ? 
This could sound silly, but I may miss something here.


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## tpd80 (Jun 28, 2011)

I've got a pretty good home made mic now. Only in about 20$ max. Did it mostly just to be able to say I did.

The issue now is finding software. I thought I had a few options but they didn't plan out well. One other ideal option the developer wants what a timegrapher would cost. So I'm still hunting for software or ill write my own up soon if nothing comes up.



Misterpeter said:


> Maybe stating the obvious, but 80$ here, adding 20$ there, a couple of 10$ on top of that etc...
> A cheap Timegrapher set is a bit less than 200$ and works well, so if you set aside the joy of the DIY (that I can understand), what's the point ?
> This could sound silly, but I may miss something here.


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## cooma (Mar 14, 2014)

This thread has helped me to make my own "timegrapher". Thanks, this was useful topic! This is my version 1.0 :










The mic is piezo element fo buzzers ( around 2 $ ) with universal preamplifier made by Kemo (around 15 $). Well ok, the signal is quite noisy without any filtering. Here is example of nonfiltering signal:










And the same signal after filtering:










My filtering method is pretty simple. I just cut off frequencies that I don't need. This is frequency distribution of the signal:










Low frequency parts is just noise and I need just freguencies between 10 - 15 kHz. After cutting other frequensies off the signal is noise free enough.

Closer look of the signal:










It's clear enough to pick up the timing, amplitude and beat error with any good software. I'm using my own sofware wich contains filtering and calculations.

This mic is useful for tuning fork watches too! For timing purpose the only thing what you have to do is look the frequency distribution and pick up the higest peak:










This is taken from Bulova Accutron cal. 214 watch. Frequency is 360 Hz as you can see.


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## Halda (Oct 15, 2013)

That's a neat project Cooma. I'm especially interested in the software; is it open source? I'm toying with the idea of building my own Arduino-based timegrapher, and having reference code would be quite useful.

No hardware filtering then, just the mic and amp, the rest in software?


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## cooma (Mar 14, 2014)

I did use Java language. It could be messy to copy it here. On the other hand my program is little bit clumsy. The results are not shown in real time. The program is runned after the sample is saved completely. 

Methods are quite commonly used, so I think it will help if I just describe those here.

For the filtering I'm using Fourier transform. Algorithm for calculating FFT (Fast Fourier Transform) should be found easily. A frequency distribution can be calculated very straightforwardly from it. Band-pass filter can be done by setting other frequency components of the FFT to 0 (or just smaller). Then the more clean signal is simply inverse transformation of this modified FFT. Unfortunately this method is quite slow to calculate. Electrical filter at least saves a calculating time. 

Picking up ticking times is done by simply setting a trigger which pick the time when signal level rises higher than trigger level. It must be the first one of the three peaks, because it is only sharp peak enough. Others are useless even if they are bigger. It is easy to believe when thinking of what causes those peaks. Then jump over "tic" more close to the next "toc" etc. If there is any disruption, there must be algorithm to reject too wrong results.

For estimating ticking frequency the program just fit a line for the previous times (vs. where they should be). This is easy to calculate by the method called linear regression (or linear least squares). Algorithm should be found easily as well.

I can answer more spesifically if needed, or send parts via email.


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## pithy (Aug 22, 2010)

cooma said:


> . . . . . . . It must be the first one of the three peaks, because it is only sharp peak enough. Others are useless even if they are bigger. It is easy to believe when thinking of what causes those peaks. Then jump over "tic" more close to the next "toc" etc. . . . . .


You may find the following interesting. If you are going to attempt to ascertain the amplitude of the balance wheel oscillation you will need the third sound. Some on the forum have have been performing wave file analysis for several years. Many use Audacity, others WaveSurfer which has various filtering algorithms. If a movement is uncased and a high quality crystal is utilized there is often enough gain to passively detect (without aid of preamplification) strong signals. Having utilized low gain amplified piezos and filtering and better crystals - I find the latter of the three most effective for my purposes.

As you are reinventing the wheel you may wish to review this link: http://delphelectronics.magix.net/etimerdemo/setup.zip


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## sidmind (Sep 30, 2013)

after spending a fair amount of time and 30 here 20 there, and so on, I never had the results I wanted trying the DIY route, I have an electronics, audio and computer background so I would have thought I would have been suited for the job.
I broke down and purchased the Acetimer for 185 and very glad I did wishing I had just listened in the first place to the guys telling me that in the first place.


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## cooma (Mar 14, 2014)

pithy said:


> You may find the following interesting. If you are going to attempt to ascertain the amplitude of the balance wheel oscillation you will need the third sound.


Yes indeed that is the case. I have amplitude estimating part too, which needs the third sound. I did mean just that it is useless for timing.



pithy said:


> As you are reinventing the wheel you may wish to review this link: http://delphelectronics.magix.net/etimerdemo/setup.zip


I have to look at that.

sidmind:

Perhaps I'm just lucky, but this my ~20 $ mic-preamplifier combination has been worked so well, that I have used it over year without actually need for better device.


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## dmmartindale (Mar 26, 2010)

Andrew McGregor said:


> So, if you use NTP, on a machine that is running Linux or MacOS (because Windows does not do NTP right), you can use the NTP-corrected timebase to measure the sound card's audio clock rate, get that nailed down, and then get a very good measure of the watch's beat.
> 
> The point is that, while there are indeed errors there, computer clocks are very consistent. The errors are not random, and you can (with a bit of work, most of which can be automated) calibrate them out.


Another method of calibration: Start with an OEM GPS receiver that has a 1 PPS (one pulse per second output). Receivers that are really designed for navigation but happen to have a 1 PPS output will produce a signal that is accurate to less than 1 microsecond most of the time. Timing-grade receivers should be accurate to a few nanoseconds most of the time. Feed the 1 PPS into the other input channel of your sound card, and digitize it along with the sound from the piezo pickup. Then, by analyzing the number of sound samples between 1 PPS pulses, you can determine the actual sound card clock rate.

If you count samples between two pulses 1 second apart, the accuracy is only one part in 48000, not very good. But count for 100 seconds and you're already under 1 PPM error in estimating the sound card clock.

Essentially, you're really comparing the watch escapement rate against GPS time, which has zero error in the long term (it's synchronized to the same sources that *define* the UTC time scale). The sound card sampling clock needs to be stable enough over a 1 second period that you can make sensible measurements of things like beat error and velocity (to calculate amplitude). But its long term accuracy and stability doesn't matter if you're actually using GPS (or NTP) as your long-term timing reference.

- Dave


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## MikeTheWatchGuy (May 23, 2009)

Now that these awesome microphones are built or being built, you may want to try the Android software Tickoprint. It's not perfect by any means, but it is cheap and does a pretty good job. Note - I have no affiliation with them and not drumming up business... merely suggesting you take a look. A user wrote that he had good experience working with an acoustic guitar pickup as mentioned here. I'm sure there are several threads here on the forum about it.


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