D. I. Y. Watch Timing Machine.

[LittleWatchShop]

4 minutes ago, CWRNH said:

This circuit supposedly is proven to work, I found it way back in this thread.

I used the schematic to create a new schematic ( below ) using TINA so I could simulate it

I then created this board based on the new schematic using express PCB

I then made the board.  It didn't work. 

It was pointed out several replies back that there was a short.  I fixed it right away and tested the board again.  Still didn't work (may have blown an IC or all of them).

So considering the original schematic was a working circuit, and I basically just copied it, it should work if I wired everything correctly.  So that being said, I must have failed miserably somewhere in translation.

Yes I do have, and have read all the tech sheets for the components, a lot of which is a bit over my head but I thought I had a decent enough grasp on it to build this simple project.  Apparently I was wrong (nothing new).  I very carefully read up on the rail splitter and thought I had it correct.

I looked over the entire board for more shorts, I found no others. 

Eventually I will learn this stuff and get proficient like you all but it takes time.  So far every new endeavor I have started has turned out successful, this one my not... LOL!  I have plenty of working timing machines, this is a project for which I hope to learn valuable skills from more than build another machine.  I have several ideas that, if I can make work, will be very useful to watchmakers like myself that actually are building watch escapements from scratch.  I appreciate all your help, and thank you all very, very, much.

LOL.  In my Junior year in college, I failed a test.  Decided that I would never be an engineer.  Woke up the next day and continued the journey.  Now I have a Ph.D., co-authored an engineering textbook now in third edition...founded a company, sold it and retired...40 US Patents...so...what am I saying?  Never give up!  OH...and I have TWO watch benches!!!

You may have blown out the first chip.  Kinda unlikely because these are pretty robust.  Remove all of the chips except the ground generator and the first opamp.  Ignore everything else.  Validate the dc voltages on the first stage before moving on.

[CWRNH]

1 minute ago, LittleWatchShop said:

LOL.  In my Junior year in college, I failed a test.  Decided that I would never be an engineer.  Woke up the next day and continued the journey.  Now I have a Ph.D., co-authored an engineering textbook now in third edition...founded a company, sold it and retired...40 US Patents...so...what am I saying?  Never give up!  OH...and I have TWO watch benches!!!

You may have blown out the first chip.  Kinda unlikely because these are pretty robust.  Remove all of the chips except the ground generator and the first opamp.  Ignore everything else.  Validate the dc voltages on the first stage before moving on.

Thank you, I will do so.

You can never have too many benches!  Or tools for that matter.  You would enjoy my shop for sure.  I have been in the business for almost 30 years.  I am lucky to have a very well equipped repair and manufacturing facility.  Tons of fun.  I also teach advanced manufacturing and CNC programming at our local Community college so I am trying to do what you are doing... teach others...

[LittleWatchShop]

2 minutes ago, CWRNH said:

Thank you, I will do so.

You can never have too many benches!  Or tools for that matter.  You would enjoy my shop for sure.  I have been in the business for almost 30 years.  I am lucky to have a very well equipped repair and manufacturing facility.  Tons of fun.  I also teach advanced manufacturing and CNC programming at our local Community college so I am trying to do what you are doing... teach others...

post your expresspcb file here.  I will make the companion schematic to validate...perhaps even send for boards.

[LittleWatchShop]

I chose a different solution and rolled my own sense amplifier.  Here is the schematic and board layout.  Boards came in last week and it is working.  I don't get quite the filtering of the opamp version, but it seems good enough.

[LittleWatchShop]

Yup...its a mess

[CWRNH]

7 hours ago, LittleWatchShop said:

post your expresspcb file here.  I will make the companion schematic to validate...perhaps even send for boards.

Components are all just generic, I didn't try to hunt down All of the exact matches for this version.

WOSUpdated on BreadBoard.rrb

[CWRNH]

7 hours ago, LittleWatchShop said:

Yup...its a mess

Pretty much the same situation here. 

[CWRNH]

7 hours ago, LittleWatchShop said:

I chose a different solution and rolled my own sense amplifier.  Here is the schematic and board layout.  Boards came in last week and it is working.  I don't get quite the filtering of the opamp version, but it seems good enough.

Very cool, can you post the files?

[CWRNH]

Here is the schematic and another version of the board. 

UpdatedOpAmp.TSC Complete board.rrb

[CWRNH]

Here is what I am getting for voltages at the Rail splitter and at the Op Amp power/Ground pins.

_________________________________________________________________

Tested without amps installed

Op amp pins between 4 and 7 show 9v - All op amps same

Op amp pins between 3 and 7 show 1.6v - All op amps same

Op amp pin from Batt + to pin 3 show 1.6 - All op amps same

Op amp pin from Batt - to pin 3 show 7.3v - All op amps same except U5 (buffer stage) shows 6.9

_______________________________________________________________________

With Rail splitter TLE2426 installed

Rail splitter pins between pins 2 and 3 show 9v

Rail splitter pins between pins 1 and 3 show 2.29

Rail splitter pins between pins 1 and 2 show 7.57v

[LittleWatchShop]

These numbers are not good.  Maybe the rail splitter is bad.

Do this.  Remove the jumper indicated in this picture.  Remove all opamps.  Only the rail splitter plugged in.

Apply power and measure between pins 1 and 2.

[LittleWatchShop]

6 hours ago, CWRNH said:

Here is the schematic and another version of the board

I dont recognize this file format.  Perhaps you are using ExpressPCBplus.  I only use their ´classic´ tool.

[JohnR725]

I'm looking at only Virtual ground wiring I would recheck all the connections. Just make sure they're going where there supposed to be. I have a hard time following part of it and it almost looks like solder bridges.

The noise reduction capacitor goes between pin 8  and pin 2.  If you look at your circuit board layout it's wired between pin 8 and 3. Then according to the image it's 1000 µF Versus the data sheet and your schematic of 1uf.

So it looks like noise reduction capacitor is the wrong physical size  wired incorrectly but it probably it's not what upsetting the voltage although it is a really big capacitor. Then because it's so much bigger than the input capacitor I'm guessing you swapped those perhaps? I would probably use a ceramic capacitor for the noise reduction rather than electrolytic.

[CWRNH]

57 minutes ago, JohnR725 said:

I'm looking at only Virtual ground wiring I would recheck all the connections. Just make sure they're going where there supposed to be. I have a hard time following part of it and it almost looks like solder bridges.

The noise reduction capacitor goes between pin 8  and pin 2.  If you look at your circuit board layout it's wired between pin 8 and 3. Then according to the image it's 1000 µF Versus the data sheet and your schematic of 1uf.

So it looks like noise reduction capacitor is the wrong physical size  wired incorrectly but it probably it's not what upsetting the voltage although it is a really big capacitor. Then because it's so much bigger than the input capacitor I'm guessing you swapped those perhaps? I would probably use a ceramic capacitor for the noise reduction rather than electrolytic.

I don't have any other shorts that I can find.  Yes the capacitor is wrong...  I have no idea how I managed that.   The via under the c19 is just a leftover I forgot to remove from the print.  It is not on the actual board.  The capacitor of 220u goes between 2 and 3, the other one is suggested on the data sheet from TI.

[CWRNH]

IT IS WORKING!  VERY NICELY!  It was the 1000u capacitor that was the problem!!  THANK YOU for all the help!  I will post more info later when I get back to the shop.

[LittleWatchShop]

Yay!

[guidovelasquez]

Thank you all for helping to resolve this issue. It is an important lesson for me.
I know the excitement when an electronics project doesn't work, but in the end it works.

[wlysenko]

I was recovering from my second covid shot and did not participate in the recent activity on this thread.

I am sorry about CWRNH's problems with the preamp he built, which are now resolved it appears. Thanks to those who helped to solve the problems.  CWRNH's circuit is based on my circuit, which is based on svorkoetter's original design. My circuit is described in the preamp noise article  at wlysenko.blogspot.com (click on link at the bottom of the page).

The schematic in my article is for my version 15 of the preamp. The latest version (no. 16) is the same except that C3 and C5 are now 0.1 uF instead of 0.47 uF and C7 is now 0.03 uF instead of 0.1 uF. These changes improve the frequency response and lower the noise a bit.

Question for CWRNH: Why are you using an LT1115 for the buffer stage? The data sheet says this part  has the lowest voltage noise, which is good, of course, but this device is not recommended for use as a voltage follower.

LittleWatchShop questioned the need for the 680 ohm resistor in the buffer stage (the data sheet uses 600 ohm in their example). It seems the AD797 opamp, which is what I used, likes to run at a high current. At high current, the voltage noise is lower, which is what we want, at the expense of some current noise.

I hope people continue to look at improving the microphone. My microphone is nearly identical to the original svorkoetter design. I found that it picks up sounds in the room  all too well. If I listen to the output with headphones, I can hear my own breathing! I think we want something that is sensitive to watch vibrations but not to sounds in the air.

[CWRNH]

4 hours ago, wlysenko said:

I was recovering from my second covid shot and did not participate in the recent activity on this thread.

I am sorry about CWRNH's problems with the preamp he built, which are now resolved it appears. Thanks to those who helped to solve the problems.  CWRNH's circuit is based on my circuit, which is based on svorkoetter's original design. My circuit is described in the preamp noise article  at wlysenko.blogspot.com (click on link at the bottom of the page).

The schematic in my article is for my version 15 of the preamp. The latest version (no. 16) is the same except that C3 and C5 are now 0.1 uF instead of 0.47 uF and C7 is now 0.03 uF instead of 0.1 uF. These changes improve the frequency response and lower the noise a bit.

Question for CWRNH: Why are you using an LT1115 for the buffer stage? The data sheet says this part  has the lowest voltage noise, which is good, of course, but this device is not recommended for use as a voltage follower.

LittleWatchShop questioned the need for the 680 ohm resistor in the buffer stage (the data sheet uses 600 ohm in their example). It seems the AD797 opamp, which is what I used, likes to run at a high current. At high current, the voltage noise is lower, which is what we want, at the expense of some current noise.

I hope people continue to look at improving the microphone. My microphone is nearly identical to the original svorkoetter design. I found that it picks up sounds in the room  all too well. If I listen to the output with headphones, I can hear my own breathing! I think we want something that is sensitive to watch vibrations but not to sounds in the air.

wlysenko, I am very thankful for your work and your schematic.  Also for all the help you and others have given.  I read your article and very much enjoyed it. 

I will try the AD797 in place of the LT1115 and see what change it makes, I will also change the capacitors as you stated above.

This amp I built from your schematic is not much noisier than my factory built machine.  I am using a vibrograf pickup instead of just a piezo disc and it works FAR better with much less background noise, it also has a much cleaner signal.  I didn't think it would work based on what I have read but to my surprise it works very well. 

As I have stated I am new to all this, but I am learning though.  I am sure I will be building several more amplifiers as time passes.  My quest for a good amp is the first step in building a special purpose machine with a few specific capabilities that will make diagnosing and building escapements much easier as well as preforming the typical timing functions. 

As I go along and learn I will incorporate the knowledge gained into a design all my own.  I am trying to design a better microphone also, and a couple other pickup devices that do not involve a traditional microphone to produce a signal.  These will be for use with some of my other manufacturing and testing machines.  Many of the machines and tools I use in my shop are purpose built by me, to solve various problems and limitations. I enjoy the process and am able to get my work done quicker with higher quality and better repeatability.  I need to create several types of triggering devices and associated peripherals.  It will be a long process for sure.

Being able to both hear and see various mechanisms in action during testing, design, and manufacturing is very helpful.  Being able to incorporate electronics, optics, and mechanics into usable devices, for my shop is my aim.

With the knowledge I have gained I have been able to build a few devices and repair some of my equipment.  My laser welder, heat treat oven, CNC mill, and CNC lathe all had issues that needed attention, all are working great now and have better reliability.  So this new dive into electronics has brought some successes for which I am grateful.......

[praezis]

Congratulations for a now working circuit!

But I still wonder, what the heck might be the reason for adding a cap C10?

Frank

[wlysenko]

41 minutes ago, praezis said:

Congratulations for a now working circuit!

But I still wonder, what the heck might be the reason for adding a cap C10?

Frank

The datasheet for the AD797 recommends a small (<33 pF) capacitor to be placed across the 100 ohm resistor to flatten frequency response. I was having a problem with a large (factor of two or three) increase in noise when the supply voltage happened to be about 8.3 V. I don't understand this behavior but the datasheet note implies a small capacitor in this part of the circuit makes a difference.  By experimentation, I found adding C10 as shown solved my problem. Maybe CWRNH can make some sense out of this if he tries an AD797.

[praezis]

Ok, I see.
But what do you expect if you run the chip below its specified supply voltage range. Even 9 V is outside (specified +/- 5 V).

I am surprised that an advanced chip like AD797 is used merely as voltage follower here, when it has the potential to replace almost the whole rest of OPs in this circuit.

Frank

[wlysenko]

4 hours ago, praezis said:

Ok, I see.
But what do you expect if you run the chip below its specified supply voltage range. Even 9 V is outside (specified +/- 5 V).

I am surprised that an advanced chip like AD797 is used merely as voltage follower here, when it has the potential to replace almost the whole rest of OPs in this circuit.

Frank

You may have a point about the voltage. No specifications are provided for supply voltages below +/- 5 V. Maybe I should be using a 12 V battery such as an A23 and forget about getting it to work at 8.2 V. I wonder if it is possible to solder wires directly to an A23.

[LittleWatchShop]

5 hours ago, praezis said:

I am surprised that an advanced chip like AD797 is used merely as voltage follower here, when it has the potential to replace almost the whole rest of OPs in this circuit.

Valid point.  My comments here are not to take away from the great work of Vorketter et al., who have contributed to this fun thread.

The additional opamps are needed for achieving the filter function.  The low-noise aspect of the design seems overstated to me.  There is about 70dB of gain at the peak (my simulation results).  If the sensor used produced an ouput of several volts p-p, let me just say that is 1Vrms to make this easy.  That means that the input signal level is on the order of 300uV.  That is a long way from the low-noise capability of these amps.  The larger concern in terms of noise, is unwanted vibration, and 60/50Hz leakage.  The circuit I posted is running here in my lab.  When I squeak my chair (as I lean back), I see the response on the scope...and I am 3-4 ft away from the sensor.  I am running closer to 50dB gain at the peak.

I suspect that replacing all of these amps with 741's would yield a similar result with the supply voltage increased (741 prefers a larger supply).

I like my circuit, but I would like more poles and zeros to get steeper skirts on the high and low sides, but nothing is for free.

[guidovelasquez]

On 3/15/2021 at 3:56 PM, CWRNH said:

IT IS WORKING!  VERY NICELY! 

Thank you very much for everyone's contributions. And how great that the preamplifier that @CWRNH built is already working. I wish to make a request: I would like to hear the output of the amplifier with the sound of a clock. The fellow @CWRNH said that he is using a microphone from an old timegrapher. I am very interested in listening to a recording. So in advance I would appreciate a few seconds of recording.

Edited March 18, 2021 by guidovelasquez
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