It's Friday and I'm bored waiting for my pizza to arrive :-) - Why not put a ring of solar cells around the center of the disc that supports the coil, with a ring of stationary high intensity LED's above them, to power the coil and on-board preamp, and then put an LED on the axis with a photodiode above it to get the signal out. No moving contacts, no long leads. Put the solar cells on the bottom and the output LED on the top of the disc to minimize any crosstalk.
-- Regards, Carl Ijames
I was thinking of using a supercap to power a diffamp. If the amplified signal comes off the spinning coil via a pair of slip rings or equivalent, the same pair of wires could be used to charge the supercap, probably through the ESD diodes of the diffamp.
A non-contact way to get the signal off would be great, but requires a lot more parts.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
In what context? If you null the capacitor charge, then do a few-seconds experiment, there's both a lower and upper frequency limit to the whole experiment.
Then you can repeat the experiment a few dozen times, and expect a gaussian distribution. Nothing about the 'DC' experiment involves day-long durations which would build up noise. The deceleration/active sensing is a few tenths of a second only.
Every phenomenon IS an artifact, that's what we're looking for.
No, it's making a controlled experiment with minimal noise sensitivity. It's experiment design. The design goal is to produce signal, not noise.
Exploration which is part of a plan, does discover things. You have no plan, except to find noise (or pickup from anbient sources beyond the scope of the investigation).
A place where one controls the circumstances, IS a lab. Every kitchen, for instance. Or darkroom. Yeah, a few oscilloscopes. Neither is relevant information for any known purpose you might have, though. Those are the wrong questions to ask.
What IS relevant, is knowledge-seeking behavior (science); finding ways (experiments) to build data to support a conclusion. Effective q/m ratio for charge carriers in metals, is a quantity to be measured, and the apparatus is a way to do that. Digitizing everything you can, is a fit to your business model, but serves no other purpose.
You pointed to a website with some guy painting boxes differently and collecting data, then talking about all the wiggles he saw. He won't ever reach a conclusion that way, he has NO HYPOTHESIS TO TEST, and all the data in the world won't give him a clue. He also has no theory of his 'noise', nor seems likely ever to generate one. Inconclusive work is... a waste of time. The boxes looked pretty, in the sunlight, though.
On a sunny day (Fri, 7 Jun 2019 11:43:20 -0700 (PDT)) it happened George Herold wrote in :
Yes
On a sunny day (Fri, 07 Jun 2019 16:47:59 -0700) it happened John Larkin wrote in :
1 laser diode in center disc shining up?= photo doide receiver
^ laser diode with simple drive electronicspowered by lithium cell ======== disk === bearing [ | ] break === bearing | [ ] spring or rubber band driving mechanism, no electric motors and fields | \0 / deserted island O experimenter \/ \/drinks O hula girls ///////////////////////////////////////////////////////////////////////////////
On a sunny day (Fri, 07 Jun 2019 12:08:56 -0700) it happened John Larkin wrote in :
Very nice. Yes I have LTspice, it runs OK on an other PC, on this one it crashes the system, probably a Linux windows emulator 'wine' fault. It sometimes makes predictions that are not reality, it predicted a video amplifier I designed would oscillate, ten boards made and no oscillations...
Nice for filters and stuff that take a lot of time to calculate by hand. There are also special filter programs though.
As to 'what spice' I was sort of joking a bit, my apologies, French fries too much mayonnaise, should not have eaten almost the whole jar...
I may have a go at building that circuit I proposed, and use a 10M 10x scope probe as collector resistor. If it turns out the Ic is already too high at room temperature, then I am wrong. Maybe be after the weekend, some other project coming up now, garden fence repair.. We had oops (garden chair flies, goes outside stores stuff), HAVE bad storms here.
I have no idea about any of this, but wonder if a rotary transformer is of any use, and my source would be from a VCR, always thought they were a bit magical. Mikek PS, not sure it won't blow apart stopping 1/2 second.
A serious lowpass filter would take all the HF stuff out; his signal is ballpark 1 Hz. But that won't work if anything rails ahead of the filter.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Are you proposing that we instrument the angular rotation of hula girls? That might require an extended series of field experiments.
I once left a woman in a volcano crater on Maui. We weren't getting along.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Hi all,
I lot of people are suggested putting the measurement circuit directly on t he rotating coil, which is an interesting idea, but has me worried on a cou ple counts. First, the coil is very heavy (2 kg) and spins very quickly (6
000 rpm), and all the mass is at the edges of the disk (20 cm in diameter) so balancing that is critical.Second, the large coils are very sensitive magnetic field detectors (unfort unately -- that's my whole problem!). So I am worried as the current flows in the circuit on the coil I will measure that current and create some sor t of unintended infinite feedback.
We used to have the speed sensor on the shaft below the coils. It was down about 10 cm below the coils. It is a little photodiode and laser that sen ses an alternating black and white strip of paper. But as the current turn s on and off in the photodiode, I could see that signal in the coil clear a s day. We had to move the motor and speed sensor 1 m away from the coils t o make it go away. So, I am worried that even a small current right on top of the coil will create enough magnetic field for my coil to pick it up.
I might have misunderstood, I though he needs to observe a sharp end of some otherwise slow electron effect. If you need only a few Hz BW, yes, then lowpass is the ticket.
At 1e9 current-to-voltage transfer ratio I am afraid that can happen easily. Worst case in spurts and that really messes up any signal.
-- Regards, Joerg http://www.analogconsultants.com/
Old rule in RF engineering: Make the gain in the first stage only as high as needed to overcome non-man-made noise. Follow with filtering immediately, and only then amplify more.
-- Regards, Joerg http://www.analogconsultants.com/
The world divides in to people who love mayonnaise (me and The Brat) and people who are repulsed by it (her sister and my wife.)
When I'm using it I hide the jar behind the toaster so Mo isn't grossed out.
It's hard to get high voltage gain from a single transistor with a resistive collector load. As the resistor goes up, you have to reduce Ic, so that reduces Ib, and Zin goes up, so there less input signal current, etc. A current source helps some.
I think the idealized transistor amplifier has a voltage gain that is
40 times the DC voltage drop in the collector resistor, something like that.We had wonderful storms in New Orleans, but the weather in San Francisco is lame. We don't even get lightning. June 8, 2019, 7AM, the temperature is 58F.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Hi all,
Again, thanks for the conversation. I can't admit I have followed it all. Here is what my current take-aways are.
John Larkin has suggested a differential amplifier for the voltages generat ed by the rotating and compensating coils.
Jan Panteltje has suggested a transistor amplifier to use the transistor as a current amplifier.
Wit3rd has suggested a charge amplifier, but one that uses a switch to keep the feedback shorted to make sure the capacitor does not send the op-amp t o the rails, then open the switch when we make a measurement.
It's not clear if any of these designs will help me with my initial concern of 60 Hz noise. Suggestions for that have included unplugging everything around the measurement system and running it at night (all good ideas), bui lding an electrostatic shielding box around the experiment, adding a 60Hz n otch filter on the input, and finally digitally removing 60Hz, 180 Hz, and
300Hz in the signal after we have collected the data.Have I missed anything vital?
Thanks!
You didn't directly respond to me, but I'm afraid a VCR rotary transformer is more of a high pass filter and wouldn't be much use at 1 HZ. Mikek
On a sunny day (Sat, 08 Jun 2019 07:08:12 -0700) it happened John Larkin wrote in :
Oops, she still there?
Now this.. Take a 74HC4046, center frequency 27 MHz, sweep 1 - 50 MHz for 1 to 5 V makes 10 MHz per volt. take the 200 nV, and put it into VCO in, this cause a frequency shift of 2e-7 * 1e7 = 2 Hz. Small antenna on output 4046.
Tune to 27 MHz with my CB narrow band FM receiver. Has about +- 5 kHz for 1Vpp out to headphone jack?
So 2 / 5000 volt .4 mV....
Maybe you can already hear that! -46dB
If you add the TIA or something with a gain of 100 at the TX side. then you get 40 mV.... Clipping is no problem... This also solves the 'how do I get the signal out' problem. Somehow I think HC4046 can be configured more sensitive? Need to read up on the datasheet and what I did in the past with it, whole lot of those chips in projects.
The CB set runs on battery, no mains needed. It has, on NBFM, very good SNR.
Would also work with my Tecsun PL600 PLL shortwave receiver, pick any frequency not in use.
On a sunny day (Sat, 8 Jun 2019 07:10:39 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in : So, I am worried that even a small current right on top
Circuit in mu-metal box?
On Jun 8, 2019, whit3rd wrote (in article):
This is cancellation, not averaging.
There are lots of schemes to cancel 1/f noise (called _drift_ when the f is low enough), and taking two samples close in time, one with the other without the sought data, and differencing is the foundation.
Here is the grand-daddy of such schemes:
.It is also the ancestor of lock-in amplifiers in general. Dicke founded Princeton Applied Research to commercialize the invention.
.. Which brings me to a thought: If the signal of interest is a few Hertz, and drifts et al are a big deal, this may be a perfect application for a chopper-stabilized amplifier of some sort.
.Not quite. There is always some residual 1/f component, and this component does not average away, and so will come to dominate. So one always has to reduce the 1/f level.
Joe Gwinn
A magnetic or optical coupler would probably need some sort of modulation, which would be a lot of electronics to spin.
One could use mag coupling into the stationary coil which is already there. Then there would only be one signal to digitize.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
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