Author Topic: Woodward's effect  (Read 494483 times)

Offline Bob012345

  • Full Member
  • ****
  • Posts: 582
  • Liked: 125
  • Likes Given: 219
Re: Woodward's effect
« Reply #1280 on: 02/14/2018 06:50 pm »
MEGA UPDATE 2/12/18

I got side tracked and purchased a 5kg load cell. I received it over the weekend and built a scale to weigh my MEGA test devices with high precision. The issue I'm having is that the load cell output changes by only ~.24nV per micro-Newton. The Op Amps I had on hand have 22nV/rtHz of input Shot noise and when I amplify the signal, this noise swamps any signal smaller than about 100uN. I have a few more tricks though.

1. I ordered some very low noise Op Amps, 3.8nV/rtHz to test.
2. I also ordered the pressure sensitive resistor for Raspberry Pi that was suggested here, as opposed to the load cell. It can support up to 10kg and has >10Mohm open circuit resistance. It will arrive this week. With that, I hope to increase the sensitivity, but it will depend on how much current the device can withstand without temperature drift.

I've probably given up on the rotary test rig. There is no way to measure forces from it, which I feel I need to do, and the slip-ring wire hub I bought is not very smooth rolling. It takes more force than I expected to make it spin and the slip-ring's drag damps it very quickly. It's also difficult to keep it aligned so that there is only torque on the slip ring and no side-to-side wobbles when I turn it on and off. Lastly, even if I cover and box both devices, I still think it will push air due to the audible vibrations attached to a long flat board. It will not have a valid outcome, regardless if it spins or not. I don't have a huge vacuum chamber to hang it in and to do it right will cost a lot more than I am willing to spend.

2/13/18 - I received the force sensitive resistor, but it does not look promising. It seems to have memory and a large hysteresis. The spec says 10% and it responds so slow I can watch it creep down from 30k, 29.98k, 29.55k... over several minutes. When I remove a mass, it takes time to spring back to higher resistance.

Regarding the noise issue, I found that the majority of noise I was measuring was coming from the power supply, so I switch to 8 "AA" batteries for my 12V supply. The low noise Op Amps will arrive tomorrow, and then I'll solder up a circuit board keeping all the traces tight to avoid noise pickup. I'll be back....

Regarding the rotary test rig, can you use a laser beam deflection, record the beam motion and from that compute the forces? Thanks.
« Last Edit: 02/14/2018 06:50 pm by Bob012345 »

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1281 on: 02/14/2018 09:04 pm »
MEGA UPDATE 2/12/18

I got side tracked and purchased a 5kg load cell. I received it over the weekend and built a scale to weigh my MEGA test devices with high precision. The issue I'm having is that the load cell output changes by only ~.24nV per micro-Newton. The Op Amps I had on hand have 22nV/rtHz of input Shot noise and when I amplify the signal, this noise swamps any signal smaller than about 100uN. I have a few more tricks though.

1. I ordered some very low noise Op Amps, 3.8nV/rtHz to test.
2. I also ordered the pressure sensitive resistor for Raspberry Pi that was suggested here, as opposed to the load cell. It can support up to 10kg and has >10Mohm open circuit resistance. It will arrive this week. With that, I hope to increase the sensitivity, but it will depend on how much current the device can withstand without temperature drift.

I've probably given up on the rotary test rig. There is no way to measure forces from it, which I feel I need to do, and the slip-ring wire hub I bought is not very smooth rolling. It takes more force than I expected to make it spin and the slip-ring's drag damps it very quickly. It's also difficult to keep it aligned so that there is only torque on the slip ring and no side-to-side wobbles when I turn it on and off. Lastly, even if I cover and box both devices, I still think it will push air due to the audible vibrations attached to a long flat board. It will not have a valid outcome, regardless if it spins or not. I don't have a huge vacuum chamber to hang it in and to do it right will cost a lot more than I am willing to spend.

2/13/18 - I received the force sensitive resistor, but it does not look promising. It seems to have memory and a large hysteresis. The spec says 10% and it responds so slow I can watch it creep down from 30k, 29.98k, 29.55k... over several minutes. When I remove a mass, it takes time to spring back to higher resistance.

Regarding the noise issue, I found that the majority of noise I was measuring was coming from the power supply, so I switch to 8 "AA" batteries for my 12V supply. The low noise Op Amps will arrive tomorrow, and then I'll solder up a circuit board keeping all the traces tight to avoid noise pickup. I'll be back....

Regarding the rotary test rig, can you use a laser beam deflection, record the beam motion and from that compute the forces? Thanks.

I considered using video frames with a laser sensor, but... the flat board vibrates like crazy and is very audible. Whatever forces I measure will be mostly from the resulting sound waves. I don't trust wrapping it up in foam and cardboard to make it silent. Besides, fiddling around with a circuit board and the load cell is a lot more my style! Still waiting for my Op amps to arrive. I have a multi-stage differential amplifier simulation complete, whose gain is 1nv to 1V of resolution. I just hope the real circuit isn't swamped by the noise.
« Last Edit: 02/14/2018 09:05 pm by WarpTech »

Offline flux_capacitor

  • Full Member
  • ****
  • Posts: 666
  • France
  • Liked: 806
  • Likes Given: 1059
Re: Woodward's effect
« Reply #1282 on: 02/17/2018 11:47 am »
As a transducer, there is not sufficient power efficiency to overcome thermodynamic limits.

As already explained by Paul March and Ron Stahl : a Mach effect thruster (MET) or Mach-Effect Gravity Assist (MEGA) drive relies on Mach's principle, it is not an electrical to kinetic transducer, i.e. it does not convert the electric energy from the power supply to kinetic energy. Rather, a MEGA drive is a gravitational transistor that develops its kinetic energy from the cosmological gravity/inertial (G/I) field locally in and out of the active mass of the thruster.

The force produced by such a thruster is supposed to grow like the square of the frequency applied to the stack, as well as the fourth power of the input voltage (unfortunately you can't increase the voltage that much because thermal expansion quickly destroys the resonance frequency, and power consumption increases too much, so you have to focus on increasing the resonant frequency). Therefore they have to develop better electronics –and maybe choose a different piezoelectric material than PZT that would have a higher natural resonant frequency– and see if the efficiency is really increasing like theoretical predictions. Precise control of the input AC voltage (shape and power) and resonant frequency determine the efficiency of a MEGA drive. Well, finding how to do this and building the right electronics is one of the goals of the 2017 NIAC contract.
« Last Edit: 02/17/2018 11:50 am by flux_capacitor »

Offline Bob Woods

  • Full Member
  • ***
  • Posts: 307
  • Salem, Oregon USA
  • Liked: 432
  • Likes Given: 1365
Re: Woodward's effect
« Reply #1283 on: 02/17/2018 06:35 pm »
Rather, a MEGA drive is a gravitational transistor that develops its kinetic energy from the cosmological gravity/inertial (G/I) field locally in and out of the active mass of the thruster.
Unqualified as I am, mechanistically any creation of mass at a quantum level requires the absorption of inertia from the universe as a whole for that mass to exist. If a quanta of energy is introduced in a manner that creates some spin, it would be effectively a boson, wouldn't it, and that would mean it has some angular momentum borrowed from the inertia of the  universe as a whole.


Can a piezoelectric lattice structure provide a matrix that imparts spin to energy quanta introduced into that structure? Likewise in the EM drive could a TE resonance contained within a moving magnetic field induce some spin into quanta of the resonant electric field?


... it make my head hurt, but I like dreaming about this stuff.


Bob
« Last Edit: 02/17/2018 06:37 pm by Bob Woods »

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1284 on: 02/17/2018 07:28 pm »
Rather, a MEGA drive is a gravitational transistor that develops its kinetic energy from the cosmological gravity/inertial (G/I) field locally in and out of the active mass of the thruster.
Unqualified as I am, mechanistically any creation of mass at a quantum level requires the absorption of inertia from the universe as a whole for that mass to exist. If a quanta of energy is introduced in a manner that creates some spin, it would be effectively a boson, wouldn't it, and that would mean it has some angular momentum borrowed from the inertia of the  universe as a whole.


Can a piezoelectric lattice structure provide a matrix that imparts spin to energy quanta introduced into that structure? Likewise in the EM drive could a TE resonance contained within a moving magnetic field induce some spin into quanta of the resonant electric field?


... it make my head hurt, but I like dreaming about this stuff.


Bob

Point taken, if the MEGA exchanges a quantum of momentum with the universe as a whole, why should/would that quanta have any more or less momentum than a photon? Photons, gravitons, dilatons are all massless particles that obey p=hbar*k.
« Last Edit: 02/17/2018 07:28 pm by WarpTech »

Offline Bob Woods

  • Full Member
  • ***
  • Posts: 307
  • Salem, Oregon USA
  • Liked: 432
  • Likes Given: 1365
Re: Woodward's effect
« Reply #1285 on: 02/19/2018 03:59 pm »
Rather, a MEGA drive is a gravitational transistor that develops its kinetic energy from the cosmological gravity/inertial (G/I) field locally in and out of the active mass of the thruster.
Unqualified as I am, mechanistically any creation of mass at a quantum level requires the absorption of inertia from the universe as a whole for that mass to exist. If a quanta of energy is introduced in a manner that creates some spin, it would be effectively a boson, wouldn't it, and that would mean it has some angular momentum borrowed from the inertia of the  universe as a whole.


Can a piezoelectric lattice structure provide a matrix that imparts spin to energy quanta introduced into that structure? Likewise in the EM drive could a TE resonance contained within a moving magnetic field induce some spin into quanta of the resonant electric field?


... it make my head hurt, but I like dreaming about this stuff.


Bob

Point taken, if the MEGA exchanges a quantum of momentum with the universe as a whole, why should/would that quanta have any more or less momentum than a photon? Photons, gravitons, dilatons are all massless particles that obey p=hbar*k.
The Higgs field is an energy quanta with spin of 0, and is massless. However, according to Wikipedia, the W and Z bosons have a spin of 1 and can have a mass greater than a proton of 80.04 GeV/c2  and 91.2 GeV/c2 but have a short half-life of 3x10-25 seconds. That would be far greater energy than a photon. In the Wiki it notes that the Z boson is a mediator of momentum transfer in neutrino scattering. Momentum transfer is what we're looking for if we're "stealing" from the universe as a whole.


I wish I understood more. I guess I'll have to keep studying  :)
« Last Edit: 02/19/2018 04:01 pm by Bob Woods »

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1286 on: 02/19/2018 05:34 pm »
...
The Higgs field is an energy quanta with spin of 0, and is massless. However, according to Wikipedia, the W and Z bosons have a spin of 1 and can have a mass greater than a proton of 80.04 GeV/c2  and 91.2 GeV/c2 but have a short half-life of 3x10-25 seconds. That would be far greater energy than a photon. In the Wiki it notes that the Z boson is a mediator of momentum transfer in neutrino scattering. Momentum transfer is what we're looking for if we're "stealing" from the universe as a whole.


I wish I understood more. I guess I'll have to keep studying  :)

I doubt there is any nuclear decay happening in the MEGA that would create W's or Z's.

MEGA Update 2/19/18

My test scale can clearly resolve a ~20mN (2g) (Thanks Monomorphic) of mass, from a calibrated weight. However, when I put the MEGA on the scale, there is over 150mV of output noise at 21kHz modulated by 60Hz. Even with the noise, I can resolve the 2g mass on, and off the scale but the MEGA just appears to be making noise. I need to decrease the noise and increase the resolution to single digits, in order to read an average weight change.

One could interpret what I'm seeing as the weight oscillating at 21kHz, but somehow I doubt it. I need to check for electrical noise getting into the amplifier breadboard.

Also, it appears that the old MEGA has very good electrostriction response at 21kHz, but the new MEGA built using new disks doesn't appear to have any. Next, I'll try applying 2 frequencies directly. I'm documenting everything for the report.


EDIT: I can clearly measure 20mN divided by 2 divisions or more on the O'scope grid. The gain of the circuit is 10^9, so 1uN ~ .24V or 240mV However, there is 120mVp-p noise when it's operating. I'm working on shielding the load cell to try to minimize the noise. twisted wires isn't doing enough.
« Last Edit: 02/20/2018 02:21 am by WarpTech »

Offline Monomorphic

  • Full Member
  • ****
  • Posts: 1435
  • United States
    • /r/QThruster
  • Liked: 3945
  • Likes Given: 1279
Re: Woodward's effect
« Reply #1287 on: 02/19/2018 11:45 pm »
My test scale can clearly resolve a ~20uN (2g) of mass, from a calibrated weight.

Please correct me if I am wrong, but I believe 20uN is 2mg-force (0.002g-force).
« Last Edit: 02/19/2018 11:48 pm by Monomorphic »

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1288 on: 02/20/2018 10:37 pm »
I am getting some very large results ~100mN (10 grams) with my MEGA Drive. However, when I flip it over, the thrust direction does not change. I am measuring weight with a load cell, and the MEGA always gains weight when energized.

The Yellow trace is the output of my differential amplifier. The calibration pulses are included in the attached results. 

Note: 5g = 5 grams, 10g = 10 grams,  “g” is grams not acceleration.

Edit 9:28PM: Turns out, the signal is just pickup-noise. It is there when the MEGA is energized even when it is not on the scale. More work is required to shield the whole setup before I can trust any data.
« Last Edit: 02/21/2018 04:28 am by WarpTech »

Offline dustinthewind

  • Full Member
  • ****
  • Posts: 699
  • U.S. of A.
  • Liked: 269
  • Likes Given: 303
Re: Woodward's effect
« Reply #1289 on: 02/21/2018 02:38 am »
I am getting some very large results ~100mN (10 grams) with my MEGA Drive. However, when I flip it over, the thrust direction does not change. I am measuring weight with a load cell, and the MEGA always gains weight when energized.

The Yellow trace is the output of my differential amplifier. The calibration pulses are included in the attached results. 

Note: 5g = 5 grams, 10g = 10 grams,  “g” is grams not acceleration.

I am curious about the exact mechanical design of your MEGA.  What parts are free to move.  What parts are bolted.  Relative masses.  Damping mechanisms.

Also curious about the load cell design.  It sits underneath I assume.  This can be done with the same material you are using to expand and contract your mega? (Pezio like material).

Is it that the device uses the weight of the table as an anchor and is accelerating the top mass?  Flipping it over still accelerates mainly the top mass?  Would changing the phase of the 2ndary signal by 180 degrees have any effect?  Do you use a 2ndary signal or use electrostriction.

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1290 on: 02/21/2018 04:39 am »
I am getting some very large results ~100mN (10 grams) with my MEGA Drive. However, when I flip it over, the thrust direction does not change. I am measuring weight with a load cell, and the MEGA always gains weight when energized.

The Yellow trace is the output of my differential amplifier. The calibration pulses are included in the attached results. 

Note: 5g = 5 grams, 10g = 10 grams,  “g” is grams not acceleration.

I am curious about the exact mechanical design of your MEGA.  What parts are free to move.  What parts are bolted.  Relative masses.  Damping mechanisms.

Also curious about the load cell design.  It sits underneath I assume.  This can be done with the same material you are using to expand and contract your mega? (Pezio like material).

Is it that the device uses the weight of the table as an anchor and is accelerating the top mass?  Flipping it over still accelerates mainly the top mass?  Would changing the phase of the 2ndary signal by 180 degrees have any effect?  Do you use a 2ndary signal or use electrostriction.

The big copper mass is about .98kg, the whole thing assembled is about 1.7kg. There are 2 pairs driven at 21.3kHz and 2 pairs driven at 42.6kHz and 1 pair used as a displacement sensor. The displacement disks can be compressed by the other stacks. The aluminum end cap is unthreaded, the copper is threaded. There are spring washers under the head of the 4-40 SS screws.

The whole rig is sitting on a 1cm thick slab of granite, on 2 "Isolate It" isolators. I'm also using a piece of foam as a damper. I have everything taped down with copper tape, grounded to the amplifier common. It runs on eight "AA" batteries, center taped for +/- 6V. However, the whole thing is electrically "floating", and is not grounded to Earth except through the O'scope, to prevent any ground loops.

Changing phase by 180 deg does change the results. It gets physically louder when the applied signals are in phase with resonance and electrostriction, and quieter when it is out of phase, but my O'scope results are mostly electrical noise. I think we should wait and see if I can resolve that issue before we trust any data I've gathered.

« Last Edit: 02/21/2018 04:45 am by WarpTech »

Offline dustinthewind

  • Full Member
  • ****
  • Posts: 699
  • U.S. of A.
  • Liked: 269
  • Likes Given: 303
Re: Woodward's effect
« Reply #1291 on: 02/21/2018 06:41 pm »
I am getting some very large results ~100mN (10 grams) with my MEGA Drive. However, when I flip it over, the thrust direction does not change. I am measuring weight with a load cell, and the MEGA always gains weight when energized.

The Yellow trace is the output of my differential amplifier. The calibration pulses are included in the attached results. 

Note: 5g = 5 grams, 10g = 10 grams,  “g” is grams not acceleration.

I am curious about the exact mechanical design of your MEGA.  What parts are free to move.  What parts are bolted.  Relative masses.  Damping mechanisms.

Also curious about the load cell design.  It sits underneath I assume.  This can be done with the same material you are using to expand and contract your mega? (Pezio like material).

Is it that the device uses the weight of the table as an anchor and is accelerating the top mass?  Flipping it over still accelerates mainly the top mass?  Would changing the phase of the 2ndary signal by 180 degrees have any effect?  Do you use a 2ndary signal or use electrostriction.

The big copper mass is about .98kg, the whole thing assembled is about 1.7kg. There are 2 pairs driven at 21.3kHz and 2 pairs driven at 42.6kHz and 1 pair used as a displacement sensor. The displacement disks can be compressed by the other stacks. The aluminum end cap is unthreaded, the copper is threaded. There are spring washers under the head of the 4-40 SS screws.

The whole rig is sitting on a 1cm thick slab of granite, on 2 "Isolate It" isolators. I'm also using a piece of foam as a damper. I have everything taped down with copper tape, grounded to the amplifier common. It runs on eight "AA" batteries, center taped for +/- 6V. However, the whole thing is electrically "floating", and is not grounded to Earth except through the O'scope, to prevent any ground loops.

Changing phase by 180 deg does change the results. It gets physically louder when the applied signals are in phase with resonance and electrostriction, and quieter when it is out of phase, but my O'scope results are mostly electrical noise. I think we should wait and see if I can resolve that issue before we trust any data I've gathered.

I think the secondary signal helps keep the electrostriction signal in the phase it is supposed to be when it overheats right?  Or is the 2nd signal just completely eliminated when hot.  When you reverse the phase of your secondary signal do you get the proper reversal of maximum acceleration or might that need to be adjusted?  It sounds like you might not be able to tell yet because of all the noise. 

Sorry for the confusion.  Fixed my missunderstanding.  So the foam is under the granite slab to damp viberations. The aluminum plate is free to move and the sensing disks and spring washers provide the damping.  The aluminum plate compressing the spring.

I wonder if eliminating Electro striction altogether might not be the easier way to go if using a secondary signal. Sorry about the confusion.  Realized what I said here doesn't make sense.  Am I correct you stated when the expanding disks when hot they lose their second electrostriction signal 2f frequency, or am I remembering this wrong.  If this is right then I guess when they are hot reversing the phase of the 2nd signal should be easy as you have no inherent 2nd signal to combat the phase change. 
« Last Edit: 02/23/2018 04:04 am by dustinthewind »

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1292 on: 03/03/2018 05:58 pm »
MEGA UPDATE 3/3/18

I put the high gain differential amplifier board in a copper shielded box, and also put the 20kHz transformers in a copper shielded box. I reconnected everything together using shielded cables and extended them so that I can put the oscilloscope and amplifier board far from the power equipment. The result is that I no longer see huge false readings at the output of the diff-amplifier. The bad news is, if there is any thrust, it is much less than .2 mN, which is the limit of my resolution right now.

The main issue now is that as the battery discharges, this tiny drop in voltage is amplified to the point where the O'scope trace is dropping at a rate of about 10mV per minute. At 1mV per division, in less than 1 minute the trace moves from the top of the screen, off the bottom of the screen. Then I have to readjust the offset voltage and start over. Hence, I have ordered some voltage regulators so I can build a battery powered, regulated, bi-polar supply for the diff-amplifier circuit to stabilize the output signals.

Readjusting the offset is no easy task either. The gain is so high that a small tweak of the 100-ohm POT causes a relatively large change in the output. I've also noticed there is quite a bit of hysteresis because the impedance of the power supply is not low enough to be unaffected by the output swing. This makes it nearly impossible to get a smooth adjustment range. Again, this is why I am redesigning the power supply to be regulated AND bi-polar, so it's not simply divided by 2 resistors. I know that the lower I make the resistors to stabilize it, the faster the battery will discharge.

The third issue is, the power amplifier seems to radiate a lot of EMI noise, even when there is no output power. As soon as I turn it on I see a haze of noise around the scope trace. (That's what you get for $57.) I'm considering putting the whole power amplifier and transformers inside a large shielded box. All these things I hope will make it so I can actually resolve the thrust the MEGA puts out down to the single-digit uN scale.
« Last Edit: 03/03/2018 06:00 pm by WarpTech »

Offline PotomacNeuron

  • Full Member
  • **
  • Posts: 262
  • Do I look like a neuroscientist?
  • MD
  • Liked: 166
  • Likes Given: 42
Re: Woodward's effect
« Reply #1293 on: 03/05/2018 02:58 pm »
MEGA UPDATE 3/3/18

I put the high gain differential amplifier board in a copper shielded box, and also put the 20kHz transformers in a copper shielded box. I reconnected everything together using shielded cables and extended them so that I can put the oscilloscope and amplifier board far from the power equipment. The result is that I no longer see huge false readings at the output of the diff-amplifier. The bad news is, if there is any thrust, it is much less than .2 mN, which is the limit of my resolution right now.

The main issue now is that as the battery discharges, this tiny drop in voltage is amplified to the point where the O'scope trace is dropping at a rate of about 10mV per minute. At 1mV per division, in less than 1 minute the trace moves from the top of the screen, off the bottom of the screen. Then I have to readjust the offset voltage and start over. Hence, I have ordered some voltage regulators so I can build a battery powered, regulated, bi-polar supply for the diff-amplifier circuit to stabilize the output signals.

Readjusting the offset is no easy task either. The gain is so high that a small tweak of the 100-ohm POT causes a relatively large change in the output. I've also noticed there is quite a bit of hysteresis because the impedance of the power supply is not low enough to be unaffected by the output swing. This makes it nearly impossible to get a smooth adjustment range. Again, this is why I am redesigning the power supply to be regulated AND bi-polar, so it's not simply divided by 2 resistors. I know that the lower I make the resistors to stabilize it, the faster the battery will discharge.

The third issue is, the power amplifier seems to radiate a lot of EMI noise, even when there is no output power. As soon as I turn it on I see a haze of noise around the scope trace. (That's what you get for $57.) I'm considering putting the whole power amplifier and transformers inside a large shielded box. All these things I hope will make it so I can actually resolve the thrust the MEGA puts out down to the single-digit uN scale.

Would you please share your diff-amp design? I happen to be an Electrical Engineer. I think a proper design should reject the common mode drift caused by the battery voltage drop. Also the pot-adjusted voltage can be made insensitive by using two stage adjustment, with a coarse adjustment followed by a fine one. Maybe your regulator should be put here instead of being with the battery.
I am working on the ultimate mission human beings are made for.

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1294 on: 03/05/2018 06:47 pm »

Would you please share your diff-amp design? I happen to be an Electrical Engineer. I think a proper design should reject the common mode drift caused by the battery voltage drop. Also the pot-adjusted voltage can be made insensitive by using two stage adjustment, with a coarse adjustment followed by a fine one. Maybe your regulator should be put here instead of being with the battery.

See attached. It's not just common mode. The load cell is also powered by the battery and so the load cell signal varies too when the battery discharges. This is then amplified by 10^9 and the resulting drift is about 10mV/Minute.  I already have multiple adjustments. Only the 1st two are significant, but the issue is not the range of adjustment. The issue is the high impedance of the ground reference, which shifts when the op-amp outputs change causing hysteresis. Hence, the need for a bipolar regulated supply to fix both of these issues.
« Last Edit: 03/05/2018 06:49 pm by WarpTech »

Offline PotomacNeuron

  • Full Member
  • **
  • Posts: 262
  • Do I look like a neuroscientist?
  • MD
  • Liked: 166
  • Likes Given: 42
Re: Woodward's effect
« Reply #1295 on: 03/05/2018 07:20 pm »

Would you please share your diff-amp design? I happen to be an Electrical Engineer. I think a proper design should reject the common mode drift caused by the battery voltage drop. Also the pot-adjusted voltage can be made insensitive by using two stage adjustment, with a coarse adjustment followed by a fine one. Maybe your regulator should be put here instead of being with the battery.

See attached. It's not just common mode. The load cell is also powered by the battery and so the load cell signal varies too when the battery discharges. This is then amplified by 10^9 and the resulting drift is about 10mV/Minute.  I already have multiple adjustments. Only the 1st two are significant, but the issue is not the range of adjustment. The issue is the high impedance of the ground reference, which shifts when the op-amp outputs change causing hysteresis. Hence, the need for a bipolar regulated supply to fix both of these issues.

I do not quite understand your schematic. It seems your Vin_H (vn_L too) feeds into a low impedance point. This is against my understanding. Also the 4 stages all look like voltage followers. How could they amplify? One thing I can say is that your voltage dividers are taking voltage from the 6V battery. This can cause the drifting. You definitely need regulated voltage to feed those voltage dividers.
I am working on the ultimate mission human beings are made for.

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1296 on: 03/05/2018 07:28 pm »

Would you please share your diff-amp design? I happen to be an Electrical Engineer. I think a proper design should reject the common mode drift caused by the battery voltage drop. Also the pot-adjusted voltage can be made insensitive by using two stage adjustment, with a coarse adjustment followed by a fine one. Maybe your regulator should be put here instead of being with the battery.

See attached. It's not just common mode. The load cell is also powered by the battery and so the load cell signal varies too when the battery discharges. This is then amplified by 10^9 and the resulting drift is about 10mV/Minute.  I already have multiple adjustments. Only the 1st two are significant, but the issue is not the range of adjustment. The issue is the high impedance of the ground reference, which shifts when the op-amp outputs change causing hysteresis. Hence, the need for a bipolar regulated supply to fix both of these issues.

I do not quite understand your schematic. It seems your Vin_H (vn_L too) feeds into a low impedance point. This is against my understanding. Also the 4 stages all look like voltage followers. How could they amplify? One thing I can say is that your voltage dividers are taking voltage from the 6V battery. This can cause the drifting. You definitely need regulated voltage to feed those voltage dividers.

The output of the load cell is a Wheatstone bridge, one corner goes up while the other goes down. The op-amps follow this trend all the way through in stages. This doubles the effective gain and helps to eliminate common mode noise.

See example on page 4, attached.

Offline PotomacNeuron

  • Full Member
  • **
  • Posts: 262
  • Do I look like a neuroscientist?
  • MD
  • Liked: 166
  • Likes Given: 42
Re: Woodward's effect
« Reply #1297 on: 03/06/2018 02:30 am »

Would you please share your diff-amp design? I happen to be an Electrical Engineer. I think a proper design should reject the common mode drift caused by the battery voltage drop. Also the pot-adjusted voltage can be made insensitive by using two stage adjustment, with a coarse adjustment followed by a fine one. Maybe your regulator should be put here instead of being with the battery.

See attached. It's not just common mode. The load cell is also powered by the battery and so the load cell signal varies too when the battery discharges. This is then amplified by 10^9 and the resulting drift is about 10mV/Minute.  I already have multiple adjustments. Only the 1st two are significant, but the issue is not the range of adjustment. The issue is the high impedance of the ground reference, which shifts when the op-amp outputs change causing hysteresis. Hence, the need for a bipolar regulated supply to fix both of these issues.

I do not quite understand your schematic. It seems your Vin_H (vn_L too) feeds into a low impedance point. This is against my understanding. Also the 4 stages all look like voltage followers. How could they amplify? One thing I can say is that your voltage dividers are taking voltage from the 6V battery. This can cause the drifting. You definitely need regulated voltage to feed those voltage dividers.

The output of the load cell is a Wheatstone bridge, one corner goes up while the other goes down. The op-amps follow this trend all the way through in stages. This doubles the effective gain and helps to eliminate common mode noise.

See example on page 4, attached.

I still can't understand your circuit. Maybe other people can shed some light on the issues I am confused with.
I am working on the ultimate mission human beings are made for.

Online WarpTech

  • Full Member
  • ****
  • Posts: 1380
  • Do it!
  • Vista, CA
  • Liked: 1431
  • Likes Given: 1904
Re: Woodward's effect
« Reply #1298 on: 03/06/2018 04:24 am »

I still can't understand your circuit. Maybe other people can shed some light on the issues I am confused with.

Exactly what are you confused with? I provided the circuit diagram on page 4 that includes the gain equation. Instead of changing to a single op-amp output, it amplifies the differential voltage all the way through. It's supposed to be less susceptible to noise.

As soon as I get some free time, I'll solder in the voltage regulators and see what happens. :)



Offline PotomacNeuron

  • Full Member
  • **
  • Posts: 262
  • Do I look like a neuroscientist?
  • MD
  • Liked: 166
  • Likes Given: 42
Re: Woodward's effect
« Reply #1299 on: 03/06/2018 05:12 am »

I still can't understand your circuit. Maybe other people can shed some light on the issues I am confused with.

Exactly what are you confused with? I provided the circuit diagram on page 4 that includes the gain equation. Instead of changing to a single op-amp output, it amplifies the differential voltage all the way through. It's supposed to be less susceptible to noise.

As soon as I get some free time, I'll solder in the voltage regulators and see what happens. :)

I think you talked about fig 5 on page 4. It is an instrumentation amplifier with two input amp in voltage follower mode, followed by a differentiation amp which actually amplifies. You took away the one stage that actually amplifies, replaced it with another pair of voltage followers. There is no amplification happening. Instead, you have  two stages of voltage followers instead. The gain is exactly 1. Even 4 stages will give you only gain = 1. [Update] sorry I misread the schematic. They can amplify. they are not voltage followers. [end Update]

Also your vin_H, vin_L are all low impedance points driven by the two amps OPA288. You can not drive that two low impedance points with your vin_H and vin_L signal.

Also it is not clear to me why the 100Hz signal is used.
« Last Edit: 03/06/2018 05:19 am by PotomacNeuron »
I am working on the ultimate mission human beings are made for.

Tags: