Raspi-powered seismometer/seismograph


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by pdenton » Mon Jul 09, 2012 12:25 pm
The python based scripts (called miniseis)were written by Jon Gilbert last year as part of his coursework at Edinburgh University. They take data from an SEP digitiser (which just produces a stream of 16 bit numbers 20 times per second onto a serial port). The code was originally written to work with the SHEEVA plug computer (an embedded linux system). The serial data comes into the SHEEVA through a USB-serial convertor. I see no reason why this should not port easily to the RasPi ( do not know whether we would need to use a USB-serial convertor or if the RAspi could read serial data directly on GPIO pins.)

The raw data is stored locally in both raw binary format (as read by Amaseis software) and also as a compressed format called miniseed (as used by seismologists all over the world). The code also broadcasts data live over a TCP connection using the same server-client protocols that AMaseis uses. It can also send data in packets to a remote web server using HTTP push. The software makes use of the Obspy python package for writing miniseed and some other functions

http://www.mutzi.co.uk/docs.tar
http://www.mutzi.co.uk/miniseis.tar
http://obspy.org

also see http://alomax.free.fr/seisgram/SeisGram2K.html for platform independant (java) seismic analysis code which reads seismic data in miniseed format

All code is open source

please feel free to email me directly if you have any queries or just to let me know how you are getting on (pdenton@bgs.ac.uk)

you might also be interested in Graeme Keon's work on using soundcards to record seismic signals
http://motivationtolearn.org/wordpress/ ... #more-1100. He uses a uses a 555 chip to modulate an audio frequency carrier with low frequency seismic signals and then record them on a cheap soundcard.
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by dgoadby » Tue Jul 10, 2012 6:29 pm
All good and gratefully received.

I already have the RPi serial port sorted out but I really want to use the I2C interface for capture if possible to simplify the process as much as possible. One option is to use the RPi with I2C to capture, filter and store the data and then the serial interface to emulate the SEP digitiser and feed it to an Amaseis. I will also be able to create data in miniseed format for compatibility with other systems when I reach the sharing stage.

Some of the code looks like it could be real time-saver. All of my code will also be available as open source and I will submit any changes/derivatives to the source groups as well.

The seismometer hardware is now done and I am just sorting out the low volume airtight lid before starting sensor tests. The electronics will be ready soon afterwards and then the RPi fun starts ;-)

I will contact you directly about items not relevant to this list.
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by allenfr » Sun Dec 16, 2012 1:10 am
Progress on this topic at all ?
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by dgoadby » Sun Dec 16, 2012 12:34 pm
Oh yes; I'm still tweaking the mechanics and the electronics to try and get a stable platform. I think I'm about there so the RPi interface is now on the bench.

I have a Wifi AP in range of where the seismometer will be permanently sited and a large solar cell designed for charging car batteries which should keep the whole thing running 365/24/7.

I will post an update once I have the RPi side up and running.
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by allenfr » Sun Dec 16, 2012 2:10 pm
Good to know. I would be interested in your mechanical side.
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by dgoadby » Mon Dec 17, 2012 1:43 am
It's a version of a fairly standard design called a Shackleford-Gundersen Seismometer. This is a 1975 design but I have updated the electronics and done all of the later improvements. A lot of folks build what is called a "swinging gate" design attributed to Lehman and it works well too but the SG unit has a smaller footprint and I just like the design better.
Once things are starting to "join up" convincingly I will post more along with some photos and, of course, the source code.

David
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by ChucktheTinkerer » Thu May 02, 2013 11:44 pm
Hi Folks:
I hope you have a good experience putting together an earthquake seismometer.
This link,
http://www.jsasoc.com/diamagnetic_suspe ... smomet.htm
describes a VERY SIMPLE novel seismometer, using a pure graphite rod suspended
in a strong magnetic field. It responds to displacement, not velocity.
There are several design issues that need to be solved to make this work properly.
I tinkered with this but lost interest. I hope someone else takes up the project.

BTW I don't think you need lots of dynamic range in your ADC. Just look at (analog) earthquake records from years ago. They managed just fine with line widths of about 1 mm and chart widths of
about 300 mm, which is equivalent to about 8 bit resolution.
In modern times there are lots of interesting cheap ways to do the ADC.

ChucktheTinkerer
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by meltwater » Thu Feb 27, 2014 12:06 pm
The schools seismograph project at http://www.bgs.ac.uk/ssp looks really promising.

I'm interested to see what electronics could be produced in order to support it and produce a low cost circuit to provide input into the Raspberry Pi (I imagine such a circuit could have multiple uses - ECGs etc). Imagine what could be done with the data using the new wolfram mathematica support.

@pdenton - ( do not know whether we would need to use a USB-serial convertor or if the RAspi could read serial data directly on GPIO pins.)
Yes - You can read serial data directly on the GPIO pins (P1 TX Pin8 and RX Pin10 are serial pins), you just need to disable the serial console first.

Interested to know what solutions would work well with this, would a multi-channel lower resolution ADC work, where each channel is set to sample specific ranges. Also what circuits are suitable for amplifying the original seismograph signal.
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by pdenton » Thu Mar 06, 2014 2:10 pm
@meltwater
we are getting there slowly with the raspberry pi seismograph. At the moment we have datalogging/viewing and analysis code running on the Raspi taking data from a USB ADC system produced by http://www.mindsetsonline.co.uk product SEP064 £59.95 The input into this ADC can be a simple homemade seismometer (at the moment I am using a simple mas on a spring design using a 0.5m perspex tube, a mini-slinky with a magnet/weight on the end and a simple coil as the sensor) The system works well as a 1hz seismometer and detects UK earthquakes very well... it can aslo detect large (>M7) events on the other side of the world but only the P waves. Seismometers like this can easily be made at home or made for about £20. We would like to reduce the cost of the ADC system and are working with mindsets to try and halve the cost of their ADC (and make it fit to the GPIO rather than USB) The adafruit 16bit ADC is very nearly good enough but lacks sensitivity for the signals we are measuring.

We will be trialling this kit in some local schools over the next couple of months and hope to be able to promote widely later on this year.

If you know of anyone interested in testing or helping development of this system please put them in touch. (either via this forum or direct to schoolseismology(_at_)bgs.ac.uk
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by BryanKerr » Mon Mar 10, 2014 6:29 am
@pdenton
I'm in the States, but I'd be interested in helping out anyway I can. I've just requested that our school K-12 school purchase one of the TC-1 slinky seismometers. If I don't get it approved, I just might build it myself anyway. I'm just about to start to diving into the Raspi, but I've got an MS in geophysics, and worked on several passive and active imaging survey's when I was in school.
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by jbeale » Tue Mar 11, 2014 12:31 am
pdenton wrote: The adafruit 16bit ADC is very nearly good enough but lacks sensitivity for the signals we are measuring.

Is it the minimum-signal sensitivity or the dynamic range that is limiting you? If the latter, you need more ADC bits but if the former, op-amps are pretty cheap and can bring up your signal level before the ADC, unless you are already near full-scale with the ambient background signal.
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by ChucktheTinkerer » Sun May 18, 2014 12:52 pm
Hi:

I followed with great interest your account of developing an earthquake seisimograph.
I enjoy making geophysical equipment, especially with the new little computers.

This fellow is recording his seismic signals using an Arduino. The Arduino has the advantage
of 1. built in ADC, 2. Easy to operate without a terminal. He has a good explanation of his signal processing.
https://www.physics.auckland.ac.nz/rese ... 52_1-1.pdf

This fellow built a nice simple seismograph and records on a PC. But you have to deicate the PC to the task.
http://motivationtolearn.org/wordpress/ ... #more-1285
hardware details are at http://motivationtolearn.org/wordpress/?p=530

I think the Arduino is a better choice than the Raspberry Pi.

Chuck Young
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by meltwater » Sun May 18, 2014 2:37 pm
Possibly an Arduino in combination with a Raspberry Pi would be suitable, with the Raspberry Pi taking over the role of the PC in your example.
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by ChucktheTinkerer » Sat Dec 13, 2014 3:22 pm
Hi:

I don't know if you are still working on your earthquake seismometer, but here are a couple URLs I found that
look promising:

Lehman style seismometer and a clever way to do the analog to digital conversion using the sound input to the computer:
http://motivationtolearn.org/wordpress/?p=1285

Seismometer sensor using a weight on a "slinky" spring:
http://scholarworks.boisestate.edu/cgi/ ... eo_facpubs

Chuck
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