I worked at a test facility in New Mexico that used those to mounter electric field. We had antenna's that we did not want lightning to hit. When the field went up we put up grounds. Except in a dust storm. A dust storm generates a bunch of high fields but no lightning. Nice project.
Nice work! I was wondering whether a mechanical shutter is the only way? Could you electronically shutter the sensing plate using a variable impedance to ground?
This was very informative and very well explained how an Electrostatic Field Mill works as well as your design. My brother and I grew up with a father who held a patient several years ago for an Electrostatic Field Mill. We also had a VDG that he designed and built that was used with his testing on a NASA project.
How did this thinking happen to you? Its not just building these "things" , but the thinking behind them. You have pushed the erector set beyond its limit, now incorporating juice cans and other loose gear. Splended!
Hi Leo, really great explanation. I think this could be interesting for weather forecast, to find out how the electric charge in the atmosphere is chained with thunderstorms and so on. Outside datalogging and comparison with the actual weather could give some interesting correlations. Excuse me for my possible bad englisch.
As an engineer, one of my greatest interest is making instruments for measuring lightning storm charges. You can measure rain drop charges, potentials off clouds and corona current from sensing antennas.
I’m a strictly a hardware guy… I can fix and re-calibrate anything as long as I don’t have to write code. or read it, or copy and paste it. 😂 But man that thing looks soooooo cool!!! And kind of complex. Reminds me of radiation detecting equipment and specifically scintillating detectors. One of my hobbies is building probes and detectors, for long range radiation detection… And specifically monitoring/logging. Scintillation detectors and probes are my favorite to build! Combining esoteric and exotic crystals, with electronics and radiation… What could be cooler!? Absolutely love your channel. If I could understand software and code like you do… I could take over the world! I just don’t have the bandwidth… After all I got into electronics completely by accident. My original business was building violins and guitars for studio musicians, using all handtools. So after a decade and a half of that… Electronics was kind of a smack in the face that I stumbled into by complete accident. Your channel kicks sooooo much ass
Wow! This is super cool! I came here from EEVBlog's channel. I still don't understand exactly how it works, but I have a better idea now. This is way beyond my knowledge of EE, I'm still a beginner, but it was interesting nonetheless!
This is incredible. Definitely earned my subscription! I'm a mechanical engineer by schooling with a love for learning electronics...I've been trying to wrap my head around these field mills for quite some time, and your "theory of operation" section finally made everything click into place. I love your chain of op-amps to measure different amplitudes. Could you possibly share which components you used for the op amps and resistance/capacitance values for the low pass filter? I'm looking to build my own with an arduino for signal processing....Looks like it might be time to finally invest in an oscilloscope as well! Anyways, thanks so much for the in depth video, and congrats on making such a beautiful field mill!
Props on such a unique device! It would be awesome to see this thing placed near a van de graaf generator or similarly large source of static potential
Awesome! I've heard about these before from some atmospheric scientists but I've never actually seen one built. Try pointing it up toward the sky and see if you can measure the voltage potential of clouds (you might need a larger device). You can predict lightning and hunt for the elusive positively charged thunderclouds.
Great stuff! Are the copper plates cut from PCB material? What to do next? Publish schematics and code... ;-) Also, waterproofing the unit and recording its response during the approach of a thunderstorm, during it, and as it recedes or dies would be interesting.
That a very good explanation on how a field mill works. I made one many years ago to measure charges of clouds during a lightning storm in Michigan. Your device could do the same. To use it in rainy and damp conditions, flip it upside down with a cover over it. It will measure the charge off the ground in reverse polarity. Such devices are used on launch pads around rockets to monitor atmospheric electrical conditions and warn of impending strikes. Corona current sensors are also used to detect lightning. I built ammeters that measure corona current using a similar circuit like your pre-amp. Very good job. Glad you shared it.
Thanks! - maybe you can help me understand this application? I understand that there is a charge gradient from the open sky, the instrument is connected to a power source at ground potential, so it's reference is ground, I just don't get how it can measure the field when pointing down at the earth? I have never seen anything used to cover the front of a mill, anything conductive obviously intercepts the field lines, any insulator can accumulate surface charges that corrupt the measurement?
@@leosbagoftricks3732 In this application, the field mill is grounded and pointed down, but it is mounted well-above the surface of the ground. Thus, some of the field lines from the sky above wrap around and enter the sensing face of the field mill. Since the measurement is indirect, a multiplying factor must be applied to convert the field strength measured by the mill into the field strength that would impinge on flat ground.
This is really cool! I am going to be building one for a senior research project for my meteorology degree. I will be using it to test the atmospheric charge during weather events. Thank you for some really good info. I'm really excited to build and test my own!
Great video, wish I'd found it sooner ;) If you want to combine it with a range measuring device (the laser thingy) you should also consider elongating the can so that you have smaller angle of incoming fields. Hope I'm clear in what I mean by that (my English vocabulary isn't that great). Just compare it to a camera and how light falls into it. You not only have a lens, but also a shroud. That shroud prevents stray light falling in from the sides. Kind a like an aperture size. That makes it more directional. Keep up the good work. Love to see more. And I found you watching the Sterling Engine --> Cool/Hot stuff ;)
Really cool build - i think i would probably code it differently though. Sample, say, 2kS per rotation for all 3 ADCs, and take the 100 or so samples closest to the antinodes (either with code or your timing trick), discard any outliers/digital filter and average them. Take whichever one of 3 the results is valid, digital filter/long term average again and use that as your output. Its a hell of a lot more processing, but well within an average MC's capability should be more reliable and accurate.
Extremely interesting, I truly appreciate your palpable passion, and all your effort and time into all such projects, Thanks very much, was already subscribed.
Wow, this is pretty cool stuff. One more remote sensing trick in the bag. I'm used to acoustic stuff (SFAI in particular), but always appreciate anything involving high voltages and HV measurements.
Really interesting project. I would love one of these gadgets to play around with. I am an ex TV man and make most things but age is against me and microprocessor I am out of touch. Cheers from old George in the UK.
Yes! Adding a distance gauge would be useful. Just add the distance gauge in a separate housing on the side of the original can - like the scope-sight they add to rifles or other weapons. 🔭
Sticking a whole bunch of tiny ones of these together to make a voltage camera would be incredibly useful. Even if the range is not great it would be increadibly valuable in quality screening of electronics, repair, or even defuising of bombs.
Plastic parts run the risk of surface charge buildup. Perhaps with conductive filament. It doesn't have to be a very good conductor. Cans are pretty cheap, though. Basically free.
Great videos, thanks! What are those clear tubes in the background with the light-saber like bases? I can make lots of guesses -- a color organ or spectrum analyzer (or those ping-pong balls or light bulbs?).. Or some other sort of measuring device? Or maybe a fun game? It sure is a mystery!
I would like to get the schematic and program you used on your AD. This would make a cool instrument to have as I re-build my old VDG. This instrument very helpful checking the static voltage level while assembling sensitive IC's.
Good design: the synchronous sanpling technique drastically reduces the effects of noise . It would be interresting if you could introduce a spoiling signal that was not effected by the rotating ground: to see to what degree the spoiling signal was rejected.
I love how you simplify complex information, could you do a resonant LLC, and break down the bonkers fractional/PEMDAS math, along with impedance matching? all while explaining it? I already love your channel, i'd love it even more if you could make a video regarding whats mentioned above!
@@leosbagoftricks3732 I'll elaborate, I am sure you know what it is, i just explained it badly. First you have a half bridge of n channel mosfets, then a series resonant tank of Lr, Cr, Lm on the primary and it is tuned specifically to the SRF of the secondary which in turn negates the reactance impedance. I want to learn more about it, I get the gist of it, it's basically making an LC resonant tank with the frequency of the secondary, I think. Every time I try to put it into practice it just doesn't seem to work, and the math is overwhelming. I am actually enrolled in college as a Biomedical engineering tech, and I'm still waiting for them to get to the portion of the course that explains more elaborate electrical math, my hobby is high voltage related stuff and making high q low intrawinding capacitance pi coils. I think you'd get a kick out of the pi coils, you should give my channel a look, or my pi coil project hackaday.io/project/184012-pi-coil-winder
Looks like something the ghostbusters would use. In your signal chain, you use inverting amps, no? So, the phase (and sign) inverts for each a2d reading?
This was a great video! Interesting subject and perfect execution. Thank you! On another note, am I going crazy or is this TheBackyardScientist's dad? 😂
Very nice build! What would be interesting is measuring a known voltage, e.g. charge a large conductive plate to a known high voltage (e.g. a few 100s of volts), hold the device a known distance apart and see if the field strength matches the theoretical value. And if you get very close, how small a surface voltage can it measure? Down to a few volts?
I checked it with a DC power supply, it reads about 936 Volts/Meter per LED. If you place the electrodes really close, it can easily detect the charge from a 9V battery.
This is an extremely cool project! I had no idea that electric field sensors like this were even a thing. I am curious why you bothered with the Hall effect sensor. You could just as easily take the derivative of the input signal and use the zero crossings to find the peaks. Also, if you could put all the gain into a single op-amp stage without clipping at higher voltages then you could use resistor divider network in place of the second and third op-amps.
Without a clean angular position reference signal, the processing of small voltage signals would fail miserably. There is significant noise on the signals, synchronous demodulation is the key to recovering the signal from the mess. If all the gain was in one stage, the output of that one stage would need to match the ADC's dynamic range. (so there is no clipping with the largest signal) Adding a resistive divider would accomplish nothing but reducing the measurement resolution. The point of auto-ranging is to make the best use of the ADC's resolution, so the dynamic range of the instrument can be very large.
Are your analog inputs to the MCU bipolar? Did you get the gains wrong? I would think that AD0 is gain -1, AD1 is gain 10, and AD2 is gain -100. Which op-amp did you use?
I always wanted to build a kind of static voltage meter that could measure the atmosphere Voltage/Height . This project triggered my imagination again. Perhaps the principles in this project could be utilized to somehow build this measuring apparatus.
I was thinking about such a device to be able to measure the voltage output of my Wimshurst generator. I may be able to use the generator to charge my workpiece for powder coating :-)
Very interesting. Take it outside, point it up at the sky, especially during a thunderstorm: Could you use it to predict or at least give some warning for lightning strikes? Should try flying it on a drone, pointed down, and log the results vs altitude... (Look up how spiders fly... there's supposed to be about 5.7x10^5 Coulombs on Earth. And, Earth is negative relative to the atmosphere at least).
Indeed, commercial versions of the field mill are used to sense the electrostatic field in the atmosphere, and very high readings (such as in excess of 10,000 volts per meter, if I remember correctly) do indicate the imminent possibility of a lightning strike somewhere nearby. Instead of pointing up, the field mill is mounted on a stand above the ground and points down so that precipitation, which would otherwise mess up the sensing, does not get inside. Even though the field mill is pointed down, some of the electrostatic field wraps around and enters the sensor. The field mill is calibrated to read out the value of the field that would be present at ground level in an open area. If the field mill is in a drone, it would need a wire to the ground to give it a known voltage reference against which to make the measurements. Flying objects can generate or accumulate a large electrical potential due to their interaction with the surrounding air. Military folks on the ground will often make contact to a helicopter, or to a payload being lowered from a hovering helicopter, with a grounding stick prior to touching the airborne object itself so as to avoid receiving a nasty shock.
This project has been revisited a few times, the first go was all-analog, producing a simple voltage output. That was a little boring, so I decided to upgrade it with a bar graph display and convert it to a digital/software architecture. It represents quite a bit of fiddling around, maybe 80 hours total?
@@leosbagoftricks3732 Do you have a list of parts you used? Currently designing the transimpedance op-amp stage and trying to decide which op amp to use with such small currents. By how much did you have to amplify the signal?
I was going to suggest to the UAP detection and documenting project GALILEO that they use field mills. Do you know of a way to make a directional array of these?
Using the counter-timer module in the CPU. Measure the period of one revolution then divide the period by 4, load that value into a counter that creates an interrupt when it expires.
Take two sheets of plywood covered in metal foil, space them a known distance. Cut a hole in the middle of one piece. Mount the meter in the hole and apply a known voltage across the plates.
I was confused about the op-amps in the schematic. Doesn't the + input need to be connected to 2.048V to center the signal? I assume you used a quad op-amp and used one to amplify the reference with a 1/2 voltage divider. So ground is really +2V.
You are right! "Ground" is centered at 1/2 the reference voltage to keep the signal centered in the ADC input range. Tried to keep this more conceptual, didn't want to drown people in details.
I had absolutely no idea that this was even possible! The thought emporium built a Wifi sensing camera that scanned across an environment and built up a picture: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-g3LT_b6K0Mc.html . That made sense to me, but to do it with this thing would be even more incredible! Question; is this an electromagnetic beam or something else? Is the voltage reading reflected like light? So many questions.
