Jump to content

hoola

Senior Members
  • Content Count

    746
  • Joined

  • Last visited

Posts posted by hoola


  1. re positioning of the 6th piezo has raised the  frequency of interest to 1.8 mhz,  much higher than I expected. Before the latest change, frequencies above 1 mhz were trivial scope fuzz. I am getting 6V p-p from this sensor arrangement. It seems productive to add more sensor piezos in this way, adding four more for complete coverage. Unless I had four more scopes, I would need to matrix the results. A decrease in the retrace delay was of course needed with this sensor change, but much less than expected.


  2. It has seemed apparent since the beginning that the sixth piezo doing the monitoring of the waveform is a problem in it's placement. I have found that putting another piezo  touching edge to edge of one in the stack offers a strong signal. The placement is like two car tires touching treads instead of sidewalls. To my surprise, the 5.5 mm thicknesses  offer a good enough physical transfer of energy to give a strong signal output, observed from face contacts. My next alteration will be to remove the sixth piezo from the stack and place it outside the stack for monitoring from the edge of the center element of the stack, offering a more linear output of overall energy flows. This way, only active elements are in the loop, and the monitor element will become a negligible factor in stack behavior. This is one more reason not to clamp the assembly too tightly,  and to use slippery poly washers between each element, allowing lateral physical movements. I have also changed the .002 cap in the enable circuit to .0039 to center up the sweet spot on the 10k delay control. Another planned change is to raise the output transistor voltage supply from +150V up to approx +250V.


  3. Using the 7014 chip with a +10V supply,  am using odd numbered outputs, 1,3,5,7,9 to drive the stack as this allows an equal time gap between pulses. The neg. feedback ckt. needs to be activated in an equal time to the total forward scan, so I have output 10 hooked to the enable pin with a .002 capacitor in series with a control set approx. at 2.7k ohms. This gives a controllable pause till you want the pulse order to begin again. I find it convenient to have all outputs hooked to LEDs, as with a fast scan one can easily tell  pulse duration of each output by relative brightness.  Individual switches to each output transistor allow base drive  to go to the transistor, or to be shunted to ground through a 1.8k ohm resistor. I have found that through adding and subtracting piezos, that a clear overlap of pulses occur at a drive frequency of 340 khz. The  stack  is one and a half inch, center to center, including 4 poly washers approx 2 mm thick and 10 thin electrode attachments of stainless steel. There is a sixth piezo at the end only used to scope the waveforms, and so not included in the length measurement but is the same 5.5 mm element. Although the sixth piezo  is passive, it does absorb and reflect the pulse, so does contribute to overall pulse speed calculations. As the neg/ feedback circuit is switched off, then back on, a clear display of removal of most harmonics is observed. The  neg. feedback circuitry is normally on only between scans. The next step is to build a non-inverting op amp twin tee circuit to insert into the signal path, which will be active during both the scan and retrace modes, with a 340 khz  notch. This hopefully will  remove  harmonics as they are being produced, without overly attenuating the 340 khz. This might make the overall trace more clear and perhaps add to pulse amplitudes by the additional removal of "noise" in the system. A possibly unavoidable source of noise is that the drive is square wave and the Woodward team says piezos like sinewaves better, but it may not make much difference at a drive frequency so much higher than the 25khz resonance. 


  4. I ordered ten 7014 ICs from Newark Electronics (formerly MCM) and all were defective.  Under close examination the logo is blurry and indistinct. I have ordered most of the parts for this project from them with no other problems.  Last week I re-ordered ten more  4017s online  from Amazon, got them today with a Texas Instrument logo  that is clear, and the first three I have tried work correctly both in the solderless breadboard and the prototype board.


  5. early mechanical experiments indicated the possibility of scavenging the return energy by dumping the reverse shock wave into a dummy load resistor.  I did get some interesting waveforms  across this load that were trapezoidal (sloping square wave) and very regular and that didn't change waveform when slowing down the stimulation.  By adjusting tensioner nut on the center pin thus adjusting mechanical pressure on each element, a sweet spot was found indicated  by a moderate compression that produced maximum voltage output on the scavenged signal.  (The woodward crowd glues and clamps each element very solidly and I think that is a problem. The elements must be allowed to move, or the shock wave is largely converted into useless harmonics). But this dummy load was only a passive load to the unwanted shock wave, so I have the active neg feedback system which should be more effective in nulling the retrace wave.  A possible way of upping the efficiency might be to try to hit each piezo, then hold the volatage on each one to the end of forward scan, then drop the voltage serially, as the shock wave travels back, thus absorbing it as much as possible within each piezo, instead of neutralizing it with the neg feedback electostriction. As the  reverse wave hits each piezo, it's loss of voltage will not only shrink in the needed direction, but the wave may compress the element slightly as it passes, thus generating a voltage that could be recycled into the next forward scan sequence. This form of retrace period might require a higher scan rate, as the piezos will collapse even if the voltage is held steady and physically self-compress at the 25khz time constant (resonance) and so require a doubly  accurate pulse timing management. The first electronic experiments will drive the stack until the temperature stabilizes,  then turning on the neg feedback system. At that point an increase in temp would seem to indicate that the return wave is being converted to heat through electrostriction...thus the possibility of thrust in the direction of reverse scan.  Still waiting for the 4017 parts, hope the corona thing doesn't significantly delay delivery. 


  6. Actually the pan balance test isn't quite so simple. A laser pointer is aimed at a mirror placed on the scale with an acute angle, and the beam is reflected onto a distant surface to display amplified small movements.


  7. I have abandoned the arduino as a trigger for the pulse delivery system due to it's apparent inability to deliver pulsed output in a microsecond range serially over the pwm ports. It does seem apparent that each one millisecond time division can be divided more finely with a hack I found online, but that seems unhelpful. I have been given a 4017 chip based design that could be capable of the needed output. It may prove easier to build what I need than to find something off the shelf.  I have also decided to skip the pendulum  idea of detection for the moment which has proven unwieldy, and will static mount the stack to start powered experiments with the goal of merging 5 small pulses into 1 large pulse, while keeping overall input power to a minimum. I have also had difficulty in the 25khz trap idea, but have found a circuit called the twin tee that does not use an inductor, only R and C components, that can be incorporated with a non inverting op amp to deliver accurate and deep rejection of a specific frequency. That is an option that can be easily added later and not necessary for the static mount tests. If the static tests prove positive, a simple pan balance setup to see if weight differences occur on a vertically mounted stack will be tried.


  8. I need to know the fastest switching speed an arduino can produce. After numerous utube tutorials and asking around, no one knows what that is. The reason I need to know is that the shock wave travelling through the stack will have to be " chased" in the manner previously described, and it seems likely that since the stack is on the order of 2" long and having a far faster speed of sound being a dense ceramic,  will need microsecond gradations, and not the millisecond pulse rates that the arduino might only be capable of.  If  the arduino speed is limited to a millisecond range,  a recommendation of a laptop controlled microcontoller with a microsecond control speed would be  very much appreciated.


  9. The drive order at each limit of swing is switched in either instance. The stack will be suspended from the ceiling with two parallel fishing lines spaced equally to the distance between stack end attachment points to keep the assembly parallel to the proposed thrust vector.


  10. the question of how to detect micro newtons of thrust is going to be a tough one for a table top experiment in the kitchen. I am going to try swinging the stack as a long pendulum of approx 55" of length,  suspended from the ceiling with fishing line. I will time the duration of the swinging without power until the mass comes to rest. Then I will power up the stack and measure swing duration with the proposed thrust direction positive to the pendulum directions. Then thrust direction will be reversed to counter the pendulum motions and that will be timed. These 3 tests averaged over many trials might offer some evidence of thrust or lack of it.


  11. a purely mechanical system is what I am experimenting with now, using a double row of 24 contacts rotary switch spinning at 1800 rpm , sweep pulsing the piezos and scoping results with a 6th piezo at the end of the stack.  I am  in the process of assembling a purely electronic setup using an arduino  microcontoller to manage timing of the 5 power amps that will pulse each element individually, with the next pulse timed precisely to reinforce the previous one in the forward direction, or hit it at the next element's  "TDC". This hopefully will result in amplification of the pulse that after 5 repeated steps hits the end of the stack, and due to mechanical impedance mismatch, is reflected back in a way similar to a transmission line or an audio amp that has lost it's load. This reflected wave is the problem. It prevents thrust by equalizing forces. The driver schematic I am  drawing up has a full time negative feedback system, but with a hi Q 25khz trap in series, which is the resonant frequency of the piezos I am using.  This will suppress  the normal sideband noise but not the desired signal.  This could clean up the carrier signal and maybe even offer some added amplification due to reduced internal losses. At the end of the cycle, when the return wave is heading back through the stack, all feedback circuits remain on, but the 25khz trap is bypassed and all signals are suppressed  maximally within each element. This hopefully will cancel a portion of the  reflected wave energy within each element. So, the overall goal is to amplify kinetic forces in one direction and actively suppress it in the other. 


  12. substances don't absorb force?  Wouldn't an absorbed force show up (at least)as heat within the material? The domed spring idea is interesting if it produces a diode like appearance to the system. The "thing" the spring is set against in this instance would be the inherent mass of the ring, but even then it seems the dome would couple as much energy overall in one direction than the other, although I see it might have a differing directional profile. If you had maxwell demons to do the job, such as tiny trap doors that all open in one direction allowing force through and close in the other, blocking such efforts with compressive release of heat from the stopped wave .


  13. does anyone know of a rubberlike substance with a tailored characteristic that passes a mechanical force in one direction, and absorbs force from the opposite direction? In effect a non linear stiffness profile, or  "smart rubber". A material of this nature could act as a rectifier of physical forces, and this directionality might offer a thrust potential when placed between each piezo instead of a single conventional damper used in the woodward mechanism.


  14. If a quantum gravity theory  contains or implies a mechanism for wormhole  structures, then we might be able to ascertain wormhole behavior and how often averaged remote entanglements might occur if the effect is global,  and if the effect is local, variations in G, or rule out such possibilities.


  15. I am working with piezo ceramics, 5.5 mm thick. I need to know the rate of a shock wave as it travels through the material.  James Woodward, et al are developing a piezoelectric Mach thruster device they are claiming develops propellantless thrust as a physical analog to the Shawyer engine. The materials to do a few simple tests are cheaply available so I figure it could be an interesting side project. Thanks for any help if you know that detail about ceramic piezos or have an interest in mach thrusters in general.


  16. if there is an entanglement field (wormholes), caused by random  disparate particles "coasting" in and out of momentary entanglements all over the universe, and this field creates a  constant average scalar pressure, could this be related to or be a component of the gravitational mechanism?


  17. can entanglement ever be "incidental", in that with all the particles in the universe,  out of mere chance could entanglement occur between  disparate particles without human intervention ?


  18. possibly a premature action to close this thread..only a few years ago the Tegmark team had a hint of G waves embedded in the CMB which might have offered the first glimpse before the bang. Unfortunately, intergalactic dust foiled the test. There is also the primal neutrino relic which may offer some results. Since there is another possible test, and a possible retesting of the CMB with improved measures, please leave this thread open. Thanks

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.