Magnetometer Project

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Magnetometer Project

Post by Carbon60 »

Hopefully this thread will be helpful to anyone considering building, installing and operating their own Earth field magnetometer to measure solar activity and its impact on our magnetic environment.

Over the past couple of years I've created and refined a simple and inexpensive device capable of detecting extremely small magnetic field deviations at the nano-Tesla scale which is more than capable of detecting events such as CME impacts http://solarscience.msfc.nasa.gov/CMEs.shtml , solar wind fluctuations created by coronal holes http://www.exploratorium.edu/spaceweather/holes.html and 'solar sector boundary crossings' http://wso.stanford.edu/gifs/HCS.html

Examples of these events and their effects on our magnetic field can be found among my posts on this site.

Over the next few days/weeks Mike G and I are going to go through and document the process of building a magnetometer step by step which I hope will be of interest.

For anyone in the teaching profession, I'd strongly encourage you to consider this as an educational project for your science classes.

Stu


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Re: Magnetometer Project

Post by marktownley »

Watching with interest :)


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Re: Magnetometer Project

Post by Derek Klepp »

A great addition for this site Stu


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Re: Magnetometer Project

Post by Montana »

I really wish I were clever enough to do this, but also I don't think my garden is well suited either. I have some electric power lines about 10m from my garden, would this render it impossible?

Alexandra


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Re: Magnetometer Project

Post by Carbon60 »

Montana wrote:I really wish I were clever enough to do this, but also I don't think my garden is well suited either. I have some electric power lines about 10m from my garden, would this render it impossible?

Alexandra
Hi Alexandra,

The power lines would make it a challenge, I think. My magnetometer recognizes my car on and off my driveway, which is also about 10m from where the sensor is located. Literally, the presence of my can distorts Earth's field sufficiently to be detected by the device, such is its sensitivity. Power lines would likely do the same although it would depend on the current running through them.

A quiet magnetic environment and good temperature stability (hence the need to bury the sensor under ground) are essential when aiming for reasonable accuracy.

BTW, the set up is really simple and most of the work required has been in refining the excel spreadsheet used for data analysis, which will be made available by me to anyone wanting to build one of these.

Cheers

Stu.


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Re: Magnetometer Project

Post by Carbon60 »

BTW, I found this on the net....
Power line magnetic field.jpg
Power line magnetic field.jpg (50.46 KiB) Viewed 6374 times
I will be helpful to anyone with similar issues with power line proximity. Given that we are speaking about solar induced fluctuations in the region of tens of nano-Tesla, then power lines will certainly be a problem, with their influence depending on the type of line (kV rating) and proximity to the sensor. Underground power cables should also be taken into account.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Magnetometer Project

Post by Montana »

I've had a look and I think it is 25KV line. I certainly can't use my compass on one half of the garden. May be the other side might be possible?

Alexandra


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Re: Magnetometer Project

Post by grimble_cornet »

Thanks Stu, I'm glad I don't have a power line within 100m or so - looks as if it would make a real mess of any attempt to detect solar induced fluctuations :o

I now have the basic parts so will have a read through the documentation before making a start :seesaw


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Re: Magnetometer Project

Post by swisswalter »

Hi Stuart

thank you very much for opening that thread. I'll follow it very closely


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Magnetometer Project

Post by Carbon60 »

Thanks for your interest, everyone.

Alexandra, unfortunately I don't think it will be possible to set one up successfully in your garden, under the circumstances. :cry:

Mike, Glad the parts have arrived. You'll also need to download the frequency analysis software Spectrum Lab http://www.qsl.net/dl4yhf/spectra1.html

First thing should be to connect everything together and demonstrate that everything works. Power up using batteries.

Cheers

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Magnetometer Project

Post by grimble_cornet »

Thanks Stu - I already have Spetrum Lab - I used to use it to detect meteors trails via FM radio tuner etc :?

Just about to post images of the main components - please feel free to correct any mistakes I make when describing them :oops:
Last edited by grimble_cornet on Thu Jan 08, 2015 10:44 pm, edited 1 time in total.


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Re: Magnetometer Project

Post by grimble_cornet »

Firstly, let me state very clearly that I am just an ignorant duffer following instructions from Stu who has 'been there and done that' already :bow


I have been very impressed with Stu's posts over the last few months and had considered having a go at building a magnetometer myself but other things got in the way.
Then, a couple of weeks ago I saw an advertisement for a Bat Detector - a 'toy' I have always wanted to own - and it reminded me that Stu's magnetometer design used exactly the same detector........................ that was justification enough for me so I placed the order and went back to studying Stu's excellent instructions which can be found here: http://solarchat.natca.net/viewtopic.php?f=8&t=10337



OK, so here we have the main components needed to construct the basic magnetometer:

The heart of the project is the FGM-3, a Magnetic Field Sensor.
It comes in a 62mm long and 16mm diameter package with 4 terminals - 5 volt power, ground, output and an internal coil which we don't need at this stage.
This version of the sensor is sold by Speake and Co. in the UK (contact details can be seen on the image) and cost 23 UK Pounds including postage.
IMG_2851.JPG
IMG_2851.JPG (202.43 KiB) Viewed 6335 times
IMG_2853.JPG
The sensor needs a +5 volt supply and eventually this will be from a regulated mains supply but at this stage I will be using 4x1.5v cells in a battery box.
IMG_2870.JPG
IMG_2870.JPG (300.77 KiB) Viewed 6335 times
The output from the FGM-3 is a 5v rectangular pulse which varies in proportion to the magnetic field strength along the main axis of the detector. This version of the sensor is very sensitive so we need to be able to detect very small changes in the output frequency. There are several circuits designs which will do this job available on the internet but Stu has come up with what I think is a very clever alternative:
IMG_2858.JPG
IMG_2858.JPG (370.21 KiB) Viewed 6335 times
IMG_2857.JPG
IMG_2857.JPG (332.06 KiB) Viewed 6335 times
The above images show an Ultrasonic Transducer - a device which converts the output from the FGM-3 into ultrasonic sound.
These transducers are available from electronic hobby suppliers etc. as they are often used in robot control systems.
This one was from Maplin - it has a central frequency of 40 kHz which nicely matches the FMG-3 output and cost just over 6 UK pounds.

We now have an ultrasound signal and Stu has found another inspirational way of dealing with this:
IMG_2860.JPG
This is a Bat Detector which is available from several outlets at a cost of about 90 UK Pounds.
Bats emit ultrasound pulses which are at a frequency which is too high for the human ear to detect - typically 20-108 kHz depending upon the species.
As the output from our Ultrasonic Transmitter is in the same range........... if we place the Ultrasonic Transmitter close to the microphone of the Bat Detector, it will treat the signal in the same way it would a bat call :P

The Bat Detector uses a simple heterodyne circuit - which in simple terms that even I can understand, works like this:
The detector generates a reference signal at a frequency (pitch) which can be varied by turning the dial (see the image above).
This reference signal is compared to the signal picked up by the microphone and a new signal equal to THE DIFFERENCE BETWEEN THEM is generated and output via a microphone.
So ~ if the bat (or our magnetometer) produces a signal of 60 kHz (too high for the ear to detect) and we tune the Bat Detector dial to 62 kHz then we will get a 2 kHz sound from the microphone which can be heard by our ears.
In effect, the high frequency bat calls are replicated at a lower pitch so that we can hear them; but we can do more than that.
The Bat Detector has an earphone socket and this can be used to transfer the audio output signal to a computer sound card where it can be recorded, manipulated and analysed.

Anyway, enough of the theory......... I now need to put the bits together and dee if they actually work :roll:
Last edited by grimble_cornet on Tue Jan 13, 2015 1:23 am, edited 1 time in total.


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Re: Magnetometer Project

Post by swisswalter »

Hi Mike

thank you very much for the details. Please be prepared to be a warehouse to supply at least one full set of the needed stuff to switzerland asp. I do not really understand what you are doing, but it is very, very interesting


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
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Re: Magnetometer Project

Post by Carbon60 »

Looking good there, Mike. It's coming together.

Please send me a PM with your email address and I'll send you the Excel file I've developed to chart the data.

Cheers

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Magnetometer Project

Post by marktownley »

You've described it very clearly there Mike, I look forward to the next chapter!


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Re: Magnetometer Project

Post by Derek Klepp »

Excellent Mike.Stu what about telephone lines?As an aside Mike when I am outside on Summer night I often have Microbats flying through my shed and have even had them snapping insects around my head.They really are a great creature.


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Re: Magnetometer Project

Post by Carbon60 »

Hi Derek,

Telephone lines shouldn't be a problem, although it is best to try to place the sensor in a spot that is furthest away from any form of magnetic interference, within reason. No need to go to the middle of the Outback! :lol:

Stu.


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Radio meteor detector.
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Re: Magnetometer Project

Post by grimble_cornet »

OK, here we go with phase two......


Here is the FGM-3 sensor connected to one end of a 25 m length of wire:
image.jpg
It is soldered and each joint covered with a short length of heat-shrink tubing before the whole area of the pins is protected by a larger diameter length of heat-shrink. The idea is to protect the joints from short circuits and to 'bulk up' the join between the sensor and the fairly fine wires.
The cable is 9-core screened data cable which I had lying around from a previous project. The individual wires are pretty fine and I would go for a 3-core version with heavier guage wires if I was starting from scratch. This type of screened cable helps to prevent signal loss and, as the signal from the sensor is fairly weak this is quite important. I was a bit worried that the fine guage wires might reduce the voltage over 25m but we will see....... I can always replace the cable if needed.

For initial testing I am using a 'breadboard' which is just a circuit board 'look alike' which allows components to be connected temporarily before final assembly - it is the blue rectangular block in the photograph shown below:
image.jpg
The breadboard is not really needed but I had it lying around in my electronics box so decided to use it for a quick play.


In the photograph, you will see the roll of cable with the three connections from the FGM-3 sensor (+5v, ground and output) going into 3 different 'rows' on the breadboard (the holes in each row - across the narrow part of the board - are connected internally).
The battery box is then connected to two of these rows providing the +5v and ground for the sensor.
Finally, the white cable connects the two wires from the ultrasonic tranducer to the ground and output pins on the FMG-3.
It sounds complicated but really only involves making 4 connections.....just make sure that they are THE RIGHT connections!
image.jpg

That completes the wiring and if we have got it right, the FMG-3 should be sending a signal to the transducer which should now be transmitting ultrasound.


As I can't hear ultrasound........... I now need to bring the Bat Detector into play. It is positioned with its microphone close to, and in line with, the ultrasound transducer and switched on.

The moment of truth............
Turn the tuning dial from its lowest frequency upwards and..... We get a loud whistling sound at 77.6 kHz which fades and then peakes again at 84.6 kHz. Tuning upwards again, the sound fades away to nothing.



:movie YES............. WE HAVE A MAGNETOMETER :movie



If you remember...the Bat detector compares the signal it receives with a reference frequency, set on the dial, and then transmits its own signal at a frequency equal to the difference between the input and reference signals. This means that NOTHING is produced when the dial is set to the same frequency as the input BUT a signal will be produced when the dial is set above OR/AND below it. If my understanding is correct (there goes another flying bacon sandwich) then this means that the FGM-3 is sending a signal at about 81 kHz = mid way between the two sound peaks from the Bat Detector.

The next stage is to connect the output from the Bat Detector to my laptop sound card so the signal can be displayed, recorded and analysed.

Watch this space.....


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Re: Magnetometer Project

Post by grimble_cornet »

Quick update.....

I managed to take the output from the Bat Detector headphone socket and feed it into the microphone socket on the soundcard of my old Win 7 laptop.
Opened up Spectrum Lab (more later) and played about until I got a reading on the screen:
image.jpg
The screen scrolls downwards as time passes...
The blue line is the signal from our Magnetomer.....fairly steady trace until....

I pass a small steel nail along a path parallel to the dectector and about 30cm (1 foot) away - you can see the result!

Moving the nail in an arc about 1m (3 feet) away from the detector produces a quite obvious deflection of the trace so we at least have a working metal detector!

All of this is with the Bat Detector on very low output volume and Spectrum Lab in basic display mode.

Turning the sensitivity up a bit results in more activity including several quite dramatic responses NOT caused by anything i am doing:
image.jpg
This thing is certainly very sensitive - might have to build a housing for it so that it can go outside away from central heating and magnetic fields generated by electrical appliances :oops:


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Re: Magnetometer Project

Post by marktownley »

Way cool! I like it! :cool:

Look forward to reading more. I caught myself looking up the bits on the internet last night...


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Re: Magnetometer Project

Post by Carbon60 »

Looking great there, Mike.

You'll find that the second (right hand) microphone on the bat detector (erm..magnetometer) is better than the left one.

Thanks for the email. I'll send you two files in return. One is a configuration file for Spectrum Lab which will set up the screen as mine with time along the horizontal axis and frequency on the vertical with sampling at 2.5 minute cadence. You can use this as a basis for your own particular colour taste etc. ;)

The second file is the Excel file to display the results (lots of number crunching to scale and filter the results). You will be able to paste the frequency/time data from a text file from Lab View for the excel file to work with.

In the meantime, here is a snapshot of one of the display configuration screens with setting used.
Configuration and display control 1.jpg
Configuration and display control 1.jpg (115.42 KiB) Viewed 6276 times
And the second.....
Configuration and display control 2.jpg
Configuration and display control 2.jpg (113.96 KiB) Viewed 6276 times
Displaying the data is one thing. You'll also need to save the data to file so that it can be manipulated in Excel. With Spectrum Lab this is easily done using the 'Export Calculated Data (Continuously) function which is selected from 'File' on the toolbar.
Export Calculated Data.jpg
Export Calculated Data.jpg (87.04 KiB) Viewed 6276 times
This gets you to the 'File Export Format' screen.
File Export Format.jpg
File Export Format.jpg (133.21 KiB) Viewed 6276 times
Click on the 'Filename and Activation' tab and you'll be able to set up a file to which data will be written (continuously at the defined cadence). Click 'Activate' and this will initiate capture.
Filename and activation.jpg
Filename and activation.jpg (139.61 KiB) Viewed 6276 times
Hopefully this will all make sense as you go through it yourself.

I'll send you the files now.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Magnetometer Project

Post by grimble_cornet »

Great stuff Stuart :bow2

I have actually got most of this set up now after an hour working through your original instruction booklet............ data is being saved at 30 second intervals as I type :P

I will use your script to set up Spectrum Lab so that we are both using exactly the same settings as that will obviously simplify any trouble shooting in the future :lol: :roll: :lol:

Got a busy weekend so probably be a couple of days before I get around to Phase 3 - be patient :lol:


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Re: Magnetometer Project

Post by swisswalter »

Hi Mike and Stuart


what a great project. Congratulations to have reached phase #2. Why is the antenna 25m long ? Do you have to burry it unfolded?


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
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Re: Magnetometer Project

Post by Carbon60 »

Hi Walter,

The 'Antenna' is actually just a connection wire to enable the sensor to be placed in a relatively remote position in Mike's garden whilst allowing it to be connected to a stable low voltage power supply and extracting the frequency signal in his house where he will keep his lap-top. All of the magnetic sensing is done by the little FGM-3 'slug' at the end of the wire.

The sensor is very temperature sensitive, so Mike will have to bury it in the garden about 0.5m below the surface or so. Clearly he has to protect it from water ingress, hence the need for a waterproof housing. All details are given in the tutorial ;)

The FGM-3 sensor is also sensitive to voltage fluctuations. It can be driven by a 6V battery supply (i.e. 4XAAs), but for a more permanent set up it is better to use a highly regulated voltage supply. The long length of connection wire to the sensor should be screened to minimise extraneous interference.

Cheers

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Magnetometer Project

Post by Carbon60 »

grimble_cornet wrote:Great stuff Stuart :bow2

I have actually got most of this set up now after an hour working through your original instruction booklet............ data is being saved at 30 second intervals as I type :P

I will use your script to set up Spectrum Lab so that we are both using exactly the same settings as that will obviously simplify any trouble shooting in the future :lol: :roll: :lol:

Got a busy weekend so probably be a couple of days before I get around to Phase 3 - be patient :lol:
No problem, Mike. We'll carry on when you are ready. I'll just set out the routine I use to transfer the recorded data from Spectrum Lab to Excel for you when you come back to it.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Magnetometer Project

Post by swisswalter »

Hi Mike and Stuart

I guess that was a stupid question from me. If I understand right. The cable is not the antenna , it is just the wirered power and signal cable to the FMG-3 sensor coming back into the house to the BAT detecter


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
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Re: Magnetometer Project

Post by swisswalter »

Hi Stuart

thank you very much for your help. While slowly understanding, you have answered my questions and did not noticed that while typing my response to my silly questions :oops:


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Magnetometer Project

Post by Carbon60 »

With Spectrum Lab up and running and data logging set, frequency data should be being written to the predetermined file every time a sample is taken, according to the settings. This will be in the form of text in Notepad.

To clean up the data, scale it and display it as a more user friendly chart I use an Excel spreadsheet (copy available on request) which I've already sent to Mike.

Here is a screenshot extract.
Excel Sheet1.jpg
To transfer the data, open the text file from Spectrum Lab and select (highlight) all date, time and frequency data for the period of interest and copy and paste into cell A8 of the worksheet. This has been written such that the text information is converted into values and column A is populated with date/time whilst column B is populated with frequency.
Excel Sheet2.jpg
Excel will then crunch the numbers and plot the charts. The time scale may require some tinkering using the formatting tool so that the exact period of interest is displayed. The Auto buttons get close, but I always find that I have to do some manual adjustment to get the axes just right.
Excel Sheet3.jpg
Vertical axis scaling of the top chart can be accomplished by changing the values in cells K3 and K4 accordingly. I usually use INTERMAGNET data from the web to fine tune my data with that of the professionals.

(We'll come on to some other refinements when you get this far, Mike).

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Re: Magnetometer Project

Post by Carbon60 »

swisswalter wrote:Hi Stuart

thank you very much for your help. While slowly understanding, you have answered my questions and did not noticed that while typing my response to my silly questions :oops:
Hey, Walter. There are NO such things as silly questions!! Better to ask and get a better understanding. That's how we all learn.

:)

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Re: Magnetometer Project

Post by marktownley »

Very interesting indeed chaps.

I'm wondering if I could do this with a wireless connection - I need to 'do away' with the wire as it is not feasible to have a long wire going from the garden to house (basically our garden is the other side of the road), power etc could be sited nearby to the vacuum flask with the FMG-3 in it, that bits not a problem, so guess it would be a wireless audio signal to a pc from the bat detector?


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Re: Magnetometer Project

Post by Carbon60 »

Hi Mark,

That would make for an interesting project!

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Re: Magnetometer Project

Post by grimble_cornet »

It certainly would be interesting Mark.
I had considered setting up an old laptop (duff battery, low spec junk) in my posh shed/observatory to interface with the sensor and then send the data to my new laptop in the house via wifi?
Left my prototype running overnight but the Bat Detector batteries were on their way out this morning after about 12 hours of use. Only cheapo batteries so Duracell or similar would probably last quite a bit longer but sounds like the power supply might be my next job once I've got the spreadsheet up and running. I've got a couple of old laptop chargers and a 2A 12v telescope power supply lying about somewhere.
I will give some thought to a container for the sensor - Mark's comment reminded me that Stuart had mentioned something about using a vacuum flask......... is this in place of the plumbing tube version in the original pdf?


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Re: Magnetometer Project

Post by swisswalter »

Hi Stuart and Mike

concerning the digging in the garden. Can't the FMG sensor be placed in the cellar of a wodden house. No steel enforced concrete floors nor walls, but of course power cabels running every where.


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Re: Magnetometer Project

Post by Carbon60 »

Hi Guys,

In my original set up I housed the FMG-3 inside a vacuum flask and put this inside a foam filled brick 'bunker' in the garden to try to minimise the effect of temperature fluctuations (to avoid burying the sensor underground with attendant risks from water ingress). However, this DID NOT WORK. The only way of minimising temperature changes I have found is to make a waterproof housing (I used plumbing accessories, but there must be plenty of other ways) and bury the sensor.

The 'bat detector' is itself also temperature sensitive, as I have mentioned, so this too needs to be in a controlled environment. For this I use a vacuum flask inside a food 'cool box', more recently fitted with a heater mat and thermostat.
DSC_0130.JPG
DSC_0129.JPG
DSC_0128.JPG
DSC_0124.JPG
I must stress that this is only because I'm aiming for better and better accuracy and closer matching with professional data. It is not necessary to go to these lengths (with the bat detector) if the objective is to just 'see' what's happening in terms of geomagnetics and look out for aurora.

Stu.
Last edited by Carbon60 on Sun Jan 11, 2015 9:23 am, edited 1 time in total.


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Re: Magnetometer Project

Post by Carbon60 »

swisswalter wrote:Hi Stuart and Mike

concerning the digging in the garden. Can't the FMG sensor be placed in the cellar of a wodden house. No steel enforced concrete floors nor walls, but of course power cabels running every where.
Hi Walter,

So long as there are no cables close by and the cellar temperature is very uniform, then this could work. I have my doubts that this could be the case, though. I initially set my system up in my garage, but the electric (magnetic) environment was way too noisy.

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Re: Magnetometer Project

Post by grimble_cornet »

OK - Phase 3:

I left the beast running over night on Friday and managed to collect some data into a text file - pretty much as described in Stuart's post above.
It all seems to be working but with vast amounts of 'drift' and 'noise' so I suspect the hard part might be getting rid of all the 'dross' :oops:

First stage was to get rid of the battery power for the Bat Detector as the 4xAAA batteries were pretty much exhausted after 24 hours.
I had an old 5v power supply lying about in 'the project box' (polite name for my spare bedroom which is full of 'vital spares' of all kinds) which should be an ideal temporary fix. Not wanting to 'modify' the Bat detector too much, I made a couple of 'dummy' batteries out of wooden dowel which hold the soldered ends of the +ve and -ve wires firmly in place in the 'nipples' of the battery compartment :P
The Bat detector was then placed in a Tupperware box surrounded by insulation material which holds the ultrasound transmitter in place next to the detector's microphone.

Second stage was to put the magnetic sensor inside another insulation filled Tupperware box and place this inside an old cool box. This was then placed outside in my posh shed/observatory. I realise that this will not satisfy the thermal stability criteria but it might improve things enough to allow me to see what is happening.

The Bat detector was re-tuned and the settings in Spectrum Lab adjusted to match what Stuart posted earlier.
Over the next hour, the frequency readings increased steadily.............. probably not a good sign.......... but as it was 1am and I had been up at 6am the previous day, it was time for a bit of sleep. I left the system running with readings been taken and written to a log file every 30 seconds (much faster than Stuart suggests but I want to monitor what is going on).

When I got up this morning I could see from the trace on the screen that the frequency had continued to rise for about 8 hours before it stabilised.
However, as soon as I started to press keys on the laptop.......... the readings started to go up again :o

I transferred the data to Stuart's spreadsheet template and, after a bit of tweaking, got a graph:
Image2.jpg
Image2.jpg (37.65 KiB) Viewed 3229 times
I popped outside for a couple of hours to do a bit of solar imaging (rubbish conditions but a man's gotta do what a man's gotta do) and when I returned the plot was starting the flatten and stabilise again :?: :roll: :?:

Stuart sent me an updated version of his spreadsheet so I set this up and transferred the data to produce 2 nice plots:
Mag Plot 1.jpg
Mag Plot 1.jpg (44.9 KiB) Viewed 3229 times
Not sure what's going on here - something is obviously causing mayhem with readings but I'm not really sure what it is.

Decided to change the batteries supplying power to the sensor - this produced a massive change to the frequency :shock:
Probably not surprising as we know that the sensor is very sensitive to voltage as well as to temperature.

I moved the Bat detector housing and the battery pack well away from the laptop to see if that would help.....
Re-tuned the Bat detector to get a good signal and set it all running and recording.

The frequency is now dropping like a stone - by about 15kHz per minute for 90 minutes so far :o

I have looked on Intermagnet and things are changing quite a bit at the moment BUT........ can't believe that it would produce this much 'one way' change in my data?


So...................

The GOOD NEWS is that the thing seems to be doing something and I have sorted out the recording, logging and analysis software :P

The BAD NEWS is that I am getting some very weird results which I don't really understand but suspect are more to do with problems in the kit than actual changes in the Earth's magnetic field :cry:

I'm still waiting for the induction coil which is supposed to go next to the sensor and reduce noise but.............. I think I will just bite the bullet and build a power supply for the magnetic sensor. If I can get rid of the batteries and have a stabilised power supply next to the sensor, things might improve - I hope :oops:

Sorry that this is turning into a novel but - it might help others who attempt the project :?:
Last edited by grimble_cornet on Tue Jan 13, 2015 1:37 am, edited 1 time in total.


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Re: Magnetometer Project

Post by swisswalter »

Hi Stuart

thank you very much. The temperature is very stable, but I think all the cables running on the ceiling kills the idea


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Re: Magnetometer Project

Post by swisswalter »

Hi Mike

thank you so much for reporting on phase 3. Absolutely great, you got plots, congratulations. Every job needs fine tuning, so don't panic ;)


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Re: Magnetometer Project

Post by marktownley »

It's a very interesting novel Mike, keep going with it.

I particularly like the whole concept as it's something completely different, but I also really like the attention to detail needed and problem solving to make it work. My 'wet weather' interests are high end hifi, and have been for the best part of 25 years now, one of the things that i've worked on with this over the years is the regulation of power supplies and also cabling (for power and audio), and, I see several parallels here that can be applied (I think!). I would dive straight into this project alas work means I don't have the time that I want to devote to it at the moment, but I can see myself starting to accumulate the parts needed with a view to possibly some holiday assembling going on.

Thanks fellas! :)


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Re: Magnetometer Project

Post by swisswalter »

Hi Mark

would you be my supplier of the parts ? All soldered ;)


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Re: Magnetometer Project

Post by grimble_cornet »

Happy to keep reporting guys.
I might be picking your brains at some point Mark if I can't get get my power supplies sorted :lol:

It seems to have stabilised again at the moment so going to let it run for a few hours while I process this morning's meagre solar harvest :oops:


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Re: Magnetometer Project

Post by Carbon60 »

Glad the interest remains, guys.

Mike, it's surprising how long it take for things to really settle down. As the sensor sits in its box it will slowly be equilibrating with its surroundings, so you'll see that the signal drift stabilises over time. It sounds like this is beginning to happen now. Using a stable power supply really is the best option. Batteries are okay to start things off, but for long-term and more accurate running a regulated supply on the sensor will bring more success.

It's looking good, though. Good to see all the elements have come together and are working to plan. Now it really is just a case of voltage regulation, stable temperature and location, location, location.

Stu.


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Re: Magnetometer Project

Post by grimble_cornet »

Thanks Stuart.
I've been having a play and understand far better now what is going on in Spectrum Lab and how you are calculating the plot in Excel.
Part of the problem is that I have several frequencies coming from the Bat 5 - seems to have got a lot worse since I have been using the power supply so I suspect that is a bit noisy. Some of these traces change together over time but a couple of them do not so I guess that they are 'noise' coming from somewhere.
Image5.jpg
Image5.jpg (127.25 KiB) Viewed 3216 times
At one point, the main trace had drifted way outside the specified logging range so Spectrum was recording a different trace altogether!

I'm rather frustrated by the fact that every time I change anything, I get a totally different output frequency which changes dramatically over time. I reset the system a few hours ago and had a nice high pitched peak signal at about 3000kH. Within a couple of hours it had dropped to 1300kH. I simply stopped the trace, changed the logging peak-frequency value and restarted......... and got an output of about 500kH which over a couple hours has climbed to over 1000kH as you can see in the screen grab shown above. Even more confusing is the fact that the trace 'jumps' every time I run my finger over the laptop touch pad :o :lol: :o :lol:

I need to source a 1 micro farad capacitor tomorrow and I can then build a stabilised power source for both the sensor and Bat 5 which will hopefully solve some of the problems. At the moment I just seem to be chasing noise from the power supply to the Bat 5 and changing voltage from the battery pack :roll:


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Re: Magnetometer Project

Post by marktownley »

grimble_cornet wrote:I need to source a 1 micro farad capacitor tomorrow and I can then build a stabilised power source for both the sensor and Bat 5 which will hopefully solve some of the problems. At the moment I just seem to be chasing noise from the power supply to the Bat 5 and changing voltage from the battery pack :roll:
I'll have a look if I have one in my box of bits in the workshop in the morning, i'll let you know...


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Re: Magnetometer Project

Post by Carbon60 »

Hi Mike,

Stabilising the power supply will make a significant difference, although there will still be more than one frequency trace displayed by Spectrum Lab. Once things have stabilised with the new power supply and once everything is in thermal equilibrium you should see things settling down. Tuning the Magenta 5 will enable you to pick out the strongest signal (around 67.7 KHz on my kit, but this will no doubt be different on yours). Spectrum Lab can then be adjusted such that only the strongest signal is displayed (by adjusting bars B and C). On your screen shot above, this would be the white line spectrum. The red lines can be faded out with this adjustment so that you don't see them. You can then set the frequency parameters on the File Export Parameters tab so that only frequencies within the defined range are exported and all other side frequencies are ignored.

Just one other thing, make sure that the sensor is pointed in the East/West (magnetic) direction.

It's all a bit of a faff, but worth the effort getting it set up properly.

Cheers

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Re: Magnetometer Project

Post by marktownley »

marktownley wrote:
grimble_cornet wrote:I need to source a 1 micro farad capacitor tomorrow and I can then build a stabilised power source for both the sensor and Bat 5 which will hopefully solve some of the problems. At the moment I just seem to be chasing noise from the power supply to the Bat 5 and changing voltage from the battery pack :roll:
I'll have a look if I have one in my box of bits in the workshop in the morning, i'll let you know...
I have 0.1uf, 2.2uf, 4.7uf, 10uf, 22uf, 47uf, 100uf - but not 1uf sadly, if any of these are any use then let me know and I will get to you. :)


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Re: Magnetometer Project

Post by grimble_cornet »

Thanks Mark - sounds like the results from raiding my box at the weekend :lol:
I actually tracked down something close and built the power supply this afternoon.

Stuart: I boosted the gain on the screen to show the multiple traces - just to make the point that there was loads of really nasty noise floating about :oops:

My understanding is that the triple-line trace at the bottom is the strongest = largest peak in graph at right of the screen?
It is certainly the last one to fade as the screen gain is turned down.

Anyway, I decided to bite the bullet today and have made quite a bit of progress.


So; on to Phase 4


Firstly, a visit to B&Q produced lots of plumbing bits and some very smelly adhesive - just like building Airfix models again with the smell of styrene cement :D :P :D
After considering a range of other options - your design seemed to offer the best solution as it was relatively cheap, waterproof and pretty easy to build. The only problem was that I couldn't find a cable gland to fit my cable but.......... an LED holder and a dab of styrene glue will do the job :lol:

Second job was to build a stable power supply using using LM7809 and LM7805 voltage regulators as per your design. This converted an old 12v telescope power supply into a regulated 5v one to power the FGM-3. I used pretty much exactly the layout from your instruction leaflet (see here if you are interested: http://solarchat.natca.net/viewtopic.php?f=8&t=10337) so there is little point in going into great detail.

The key point is that with the new power supply the trace is clean and most of the additional traces have gone - there is a second much weaker frequency from the Bat 5 but that is easy to ignore.
This is what I now see with very high screen gain:
Less noise with 5v.jpg
Less noise with 5v.jpg (99.28 KiB) Viewed 3185 times
And with the gain adjusted to show just the main trace:
new 5v trace.jpg
new 5v trace.jpg (91.46 KiB) Viewed 3185 times
As I already have a 5v power supply for the Bat 5 and all seems to be working..... I didn't bother to take another 5v supply from the 12v source but I may do that in the future if only to reduce the number of sockets required :lol:

For the moment the FGM-3, enclosed in it's new housing, is outside in my shed and the frequency trace is dropping steadily - I suspect the 15 degrees C temperature difference between the house (where it was constructed) and the shed is the main reason.
90 minutes on 5v power supply.jpg
90 minutes on 5v power supply.jpg (34.59 KiB) Viewed 3185 times
After about 90 minutes the trace seems to be flattening out so...... we will see what happens overnight.

If things look good, I will then bury the sensor package in the garden; but strong winds and heavy rain make that look rather unattractive at the moment :oops:

Watch this space for an update tomorrow :roll:
Last edited by grimble_cornet on Tue Jan 13, 2015 4:33 pm, edited 1 time in total.


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Re: Magnetometer Project

Post by swisswalter »

Hi Mike

that whole story is like a crime. I love it. May it have 777 pages ;)


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Re: Magnetometer Project

Post by grimble_cornet »

Thank you Walter - like the best crime thrillers, I try to finish each instalment with a 'cliff hanger' ........... what will happen next :?: :roll: :?:


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Re: Magnetometer Project

Post by Carbon60 »

Excellent progress, Mike. You'll see some variation as the temperature dips over night in your shed, but once the sensor is buried you'll have yourself a fully functioning magnetometer :cool: :D :cool:

Remember it has to be straight and level in the East-West direction. A wet mix of cement will give you a flat/level base at the bottom of the hole and attaching the pipework to a paver will give it weight and stability during backfilling to stop it moving out of alignment.

Let's hope the weather cooperates! Good luck.

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