Category Archives: Electronics

KickSats - An Interview with Zac Manchester

Posted on March 6, 2014 | Leave a comment

Another AGU related post, but this time one that offers a future opportunity for participation! While walking around the vendors areas I approached a space company and began talking with a student at their booth. He turned out to be Zac Manchester, the main driver of the KickSat campaign. We chatted for a bit and I thought this would make a great post as well as letting you know about an upcoming opportunity to help telemeter data down.

Zac Manchester showing off an example satellite at the AGU Fall Meeting.

Zac Manchester showing off an example satellite at the AGU Fall Meeting.

You can find out some about the project from KickSat.net. After the meeting Zac was kind enough to answer some questions for the blog. There will be a future post as well where I'll share my personal ground station setup and then posts during reception of the data in Feburary. It's fun to see these tiny satellites that are just a printed circuit board with a solar cell and no battery. Amazing design and great use of a Texas Instruments microchip with a built in radio! Zac actually repurposed these chips as they are designed to be used in wireless key entry systems in cars. Fantastic!

What inspired you to start the KickSat program?
Mostly desperation. Our research group at Cornell has been working on
"ChipSat" scale spacecraft for a number of years and we got to a point
where we felt we were ready to actually fly some in space. We were
able to get a free launch through a NASA program called ELaNa, but we
still needed some money to build the flight hardware. KickStarter was
still pretty new at the time (2011), but I had heard of it through
some friends. After thinking it over a lot and not really having many
other options, we decided to go for it.

What was the most difficult challenge during the project?
The most difficult technical challenge was probably the communications
system. We're trying to simultaneously receive signals from over 100
tiny satellites, each with only about 10 mW of power, from 500 km
away, all on a very low budget.

How will the satellites be deployed and where can we find tracking data?
The Sprites will be deployed out of a 3U CubeSat "mothership" (called
KickSat), which is being launched on a SpaceX Falcon 9 in late
February or early March. The Sprites will be deployed 7 days after
launch vehicle separation and we will have tracking data available on
our website (kicksat.net).

When is launch?
Officially February 22, 2014, but that will likely be subject to delays. This is now set for March 16, 2014.  You can check for updates by looking for spacecraft "SpaceX CRS 3" on  SpaceFlight Now.

How long will the satellites be in orbit?
KickSat, the 3U CubeSat "mothership" will stay in orbit for a few
months, while the Sprites will reenter in a few days, probably less
than a week, after they are deployed.

How can educators and radio operators receive the data? How should be send in any data we receive?
We'd love to have participation from as many radio amateurs as
possible. Information on how to set up a ground station, receive
signals, and submit recorded data will be posted on kicksat.net in the
coming weeks.

That's it! Thank you for reading and be sure to check out any follow up posts.  I'll be setting up my ground station over the next week.

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Posted in Amateur Radio, Education Opportunity, Electronics, Space

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Never Confuse Chip Pinouts Again!

Posted on February 11, 2014 | 4 comments

chip_labels

 

UPDATE: John Meacham commented below letting us know that he has updated the package.  It can now be installed with it's new features by installing the packages I mention below and then:

>>  sudo apt-get install libfile-slurp-perl
>> apt-get install darcs
>> darcs get http://repetae.net/repos/clabel

This is a topic of interest to a rather limited group, but one well worth posting I believe.  Those who build electronic circuits regularly know the pain of constantly swapping back and forth between datasheets when trying to remember which pin of an integrated circuit does what.  It's different for almost every chip and can slow down prototyping when you're on the fly or don't have internet access.  John Meacham over at Not A Number  decided to remedy this problem after noticing that 6mm tape from a Brother label printer fit perfectly on top of his chips!

You can find his Perl script over here, but I wanted to elaborate on how to get it working and my experience with it thus far.  I ended up running the code on an Ubuntu virtual machine with Parallels.  I had lots of problems getting the libraries needed to run on Mac OSX, but the Linux install took just a few minutes.

First, download and unzip the files from John's website.  There is a read-me telling you how to run the scripts, but we don't get there just yet.  First we must install the GD module for pearl and the cups-bsd for printing utilities.  To do so, follow these two commands:

>>  sudo apt-get install libgd-gd2-perl
>>  sudo apt-get install cups-bsd

Since we're going to make our own custom labels as well, we'll need two more packages.  The barcode and YAML packs.  Just run:

>>  sudo apt-get install libconfig-yaml-perl
>>  sudo apt-get install libgd-barcode-perl

Okay, now we need to install our printer.  Just plug in your Brother printer and follow the normal steps to install it just like any other device.  Ubuntu automatically found the drivers for me and set it up.

Next I just printed out a 555 timer IC label to get started.  My printer is called labelprinter, so the command was:

>>./print_png.prl -Plabelprinter -w 6 out/555.png

The label printed out! Now I did notice that sometimes there is some garbage at the beginning of the label, but I trimmed that off with scissors anyway.  I do wish there was a way to prevent the printer from feeding and cutting after every label though, it wastes some label tape.  There may be a way to modify the scripts.

While there are a few included labels, you'll want to make your own eventually.  This is done with YAML.  Let's make a label for the 74LVC244A octal buffer/driver.  First we'll look at the datasheet (here) and get the pinout.  Below is the screen-shot of the datasheet spec.

pinout

We must write a YAML file to describe this pinout:

74hc165:
name: 74hc165 - PISO register
pins:
- /PL
- CP
- D4
- D5
- D6
- D7
- /Q7
- GND
- Q7
- DS
- D0
- D1
- D2
- D3
- /CE
- Vcc

The / before the pin will add the overbar to indicate the active state of the pin.  The YAML code is added to the file chips.yaml and we run the script:

>>   ./chip_label.prl -c 74LVC244A

We now have a new label to print and affix to our chips! 74lvc244a

There we go! Sorry this was a bit lengthy and technical, but this tool is incredibly useful for anyone involved with prototyping!

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Posted in Electronics, Hardware, Software

Favorite Books and Products of 2013

Posted on December 30, 2013 | 1 comment

This year, like every other, was full of lots of great, okay, and no so good things. Being the list-oriented person that I am, it seemed appropriate to list out great things of the year. While there were many things that could go here (favorite trips, etc), I thought keeping with the orientation of the blog we should look at the favorite books and products of the year. Not all of these came out in 2013, but I discovered them all in 2013. Without further delay:

Favorite Books

In Suspect TerrainIn Suspect Terrain - John Mcphee
 This book reads like a novel, but gives massive geologic context. It is part of a series that I will continue reading this year. If you are curious about the geologic history of the east, this gives a driving cross-section and great context.

Scientific PresentationsThe Craft of Scientific Presentations - Michael Alley I was fortunate enough to attend my 2nd Michael Alley workshop this year and gained much from both it and his book. Dr. Alley is a phenomenal person that is full of energy. His presentation advice helped me give an AGU talk, as well as successfully pass my candidacy exams (those should probably be posts).

EE 101Electrical Engineering 101 - Darren Ashby I've seen this book for quite some time, but decided to give it a read and see what it was like. Overall it was a great intro to electronics for new-comers and a good review for those who, like me, perform lots of electronics hobby work, but are not professional engineers. A few of the analogies were somewhat wrong at anything more than the basic level, but that's what they were there for.

GuesstimationGuesstimation: Solving the World's Problems on the Back of a Cocktail Napkin - Lawrence Weinstein A fun read that helps speed up your order of magnitude estimation capabilities. These were great lunch-hour exercises.

Command and Control

 

Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety - Eric Schlosser Having lived in Arkansas for most of my life, this book was of interest to me. I was quite surprised at just how unsafe much of the nuclear arsenal was and how many close calls we have had.

Feynman's RainbowFeynman's Rainbow: A Search for Beauty in Physics and in Life - Leonard Mlodinow Recommended to me by a professor in the department, this was a quick read that gave an outside look at the life of Richard Feynman from one of his colleagues. A must for any Feynman fan or general physics reader.

Data PointsData Points: Visualization That Means Something - Nathan Yau Another stellar book from Natan Yau of flowingdata.com. Great advice on presenting complex data in an easy to digest form.

Zen

 

Zen and the Art of Motorcycle Maintenance - Robert M. Pirsig Sometimes I will read a classic, and this did not disappoint. Very quotable and very enjoyable.

 

Favorite Products

Timbuk2Timbuk2 Classic Messenger Bag I didn't want to carry my leather briefcase throughout Italy and Holland this summer, so I ended up with this bag. I can't say enough about how durable it is and what a great traveling companion it makes. I have notice many geoscience folks carry these and believe that they should sponsor AGU.

Blackwing 602Palomino Blackwing 602 Pencils A post in the "How I Work Series" mentioned these and I must say that they are the darkest pencils I've seen. I generally use pen in my notebooks, but these are great replacements.

Beaglebone

 

Beaglebone Black This is the new small/embedded computer design. I'm implementing them in my infrasound bucket project and in a few others.

Hakko

 

Hakko FX-888D Soldering Station This is my new go-to soldering station for those of us on a budget.

 

USRP Software Defined Radios While expensive, I got to use some of these in a recent project and make a radar out of them!
USRP

What did I miss?

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Posted in Administrative, Education Opportunity, Electronics, General Science, Geology, Reviews

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Quick Test of Geophone Response

Posted on September 13, 2013 | Leave a comment

I just wanted to post a quick article about geophones.  Geophones are essentially instruments that allow us to measure the velocity or acceleration of the ground.  Yes, seismometers do this, but generally when we refer to geophones we are talking about single sensor (almost always vertical sensing) devices used for seismic imaging in oil/gas exploration.  I've talked about seismic surveys before (here for example). The "element", or the actual sensor is pictured below.  These sensors have a magnetic element on a spring inside a coil of wire.  Motion of the magnet (resulting from ground motion) generates a small electrical potential in the coil.  If I can find a cheap element/case on eBay I'll do a teardown of one in the future.  The signal generation happens through a process called "electromagnetic induction", described by Michael Faraday in 1831!  Want to know more about induction? Head over to the wikipedia page or shout out and we can put together a demonstration.

Dr. Ammon, whose office is next door, brought over an old element that he wanted to compare with our seismometers in the basement of the building.  Not knowing the output voltage range well, we hooked it up to a Rigol DS1102E oscilloscope on my desk.  I set the trigger of the oscilloscope (when it started collecting data) to just above ground potential so that any appreciable motion will trigger data recording.  We recorded the voltage output of the sensor about 6800 times per second!

The sensor element from a geophone.  (Image: Ebay)

Below is the waveform collected from hitting my desk with moderate force.  Surprisingly these elements put out +/-4 Volts! When shaking the element to it's limits we were seeing voltages of around +/- 10 Volts.  To me this indicates there are many turns in the coil and a very strong, probably rare earth, magnet inside.  Measurement of the coil resistance or a teardown will tell if this is correct! I've also included the power spectral density for those of you interested.  These figures tell us about the frequency response of the instrument.  Depending on how the spring system is setup, the oscillator is very sensitive to some frequencies and not so sensitive to others.  These diagrams help us characterize this response.  

Collected waveform from hitting my desk.
Power Spectral Density

Power Spectral Density: Zoomed in

Sorry for the short post, but I just wanted to share a quick desktop experiment!

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Posted in Electronics, Geophysics, Hardware

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Fluxgate Magnetometer Wrap-Up (For now)

Posted on December 26, 2012 | 6 comments

Per lots of emails and requests I’m going to post what I have from the design of the fluxgate magnetometer mentioned in several previous posts (like this one).  The schematic attached at the bottom is a rough draft, but should provide some guidelines for designing and building a version of this instrument.  I’ve also attached links to several PDFs that I found very helpful when building this demo.

It should be noted that this design doesn’t have a plain readout with XXXXXX nT magnetic field, but displays a waveform on the oscilloscope.  Could one be made? Absolutely! Since this was more of a demonstration of the underlying physics I didn’t bother, but it would be a good weekend project.

First off let me list a few things I would build differently were I building this again:

-       Use shielded lead wires to reduce crosstalk to the coil.

-       Use a simple Analog-to-Digital converter so this output is projected from a laptop to the classroom screen (much easier than gathering students around an oscilloscope).  I think an Arduino might do the trick.  Raspberry Pi would be a good choice too.

-       Add gain adjustment knobs to the control panel.

-       I would again use the Velleman kit for the signal generator instead of re-designing the wheel.

When using this in the classroom I laid it alongside commercial magnetometers on the table.  We discussed the physical principles behind the instrument, and then students would use the demo fluxgate to generate an output wave.  Afterwards we used the commercial magnetometers to do simple tasks like finding conduits and keys. 

It would also be nice to have a first-principles proton-precession magnetometer.  There is a book “Signals from the Subatomic World: How to Build a Proton PrecessionMagnetometer” that describes one such instrument, but significant improvements in the instrument could be made with modern programming languages and ADC devices. 

I still welcome questions on the fluxgate and will probably update the instrument next time I teach an Intro Geophysics course (undetermined).  Thank you for all the interest and if you build one, please send your results and we’ll put them up here for all to benefit.  

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Posted in Education Opportunity, Electronics, Geophysics, Hardware, Projects

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3D Printing in the Lab - Will Lab Hardware Follow Software into Open-Source?

Posted on September 15, 2012 | Leave a comment

Today I read the article "Building Research Equipment with Free, Open-Source Hardware" by Joshua Pearce from a recent Science Perspectives section.  I'd like to share some thoughts on the article as I thought it introduced what may be the next "want" item in many labs.

In the modern scientific lab there is a large assortment of sophisticated hardware necessary to conduct increasingly complex research.  Generally scientific hardware is some combination of turn-key or off the shelf equipment and equipment designed and built in house.  In recent years laboratory software has progressively become part of the free and open-source software (FOSS) movement; hardware is now following the same trend with the advent of open-source 3D printers from the hobbyist community.

Open-source hardware became popular in the late 90’s with the basic stamp “board of education” microcontroller circuit boards, but the Arduino has taken over the hobby market with its $30 price tag.  Arduino has a number of modules, or shields as they are called, ready built with significant code libraries available.  With the Arduino circuit boards scientists can perform basic hardware control with digital and analog outputs in addition to basic analog-to-digital conversion.  

The RepRap open-source 3D printer is driven by the Arduino and can be constructed for <$1000.  The machine prints the parts required to make another RepRap printer, so building a machine is approached by entering the RepRap community with a parts request.  Users also post 3D designs on Thingiverse for download and printing by anyone.  A sufficient amount of laboratory equipment from test tube racks and filter wheels to Dremel tool adapters are already online.  

Printing laboratory equipment may not only reduce the cost of research, but allow the same flexibility, innovation, and rapid development cycle enjoyed by scientific software.  Being able to create a custom bracket, holder, mold, or sample jig could be advantageous to almost any laboratory and allow research to be conducted more efficiently with less focus on coordinating development with engineers at commercial manufacturers.  The open-source nature of the parts library will reduce duplication of work between those in a common field of research and allow cross-lab standardization of sample preparation techniques.  

There are limitations to what can be easily constructed in the lab, such as 3D printing with metal.  The technology to do this exists, but is too complex and expensive at the present time for individual applications.  While working at Oak Ridge National Laboratory I got the opportunity to see 3D printing with titanium.  The video below is a titanium ball... bouncing. (Apologies for the portrait video and quality, this was taken several years ago with an early iPhone.)




Like all community projects, the RepRap is being updated to have greater capabilities.  According to the project website a major milestone will be printing with electrical conductors to manufacture rapid prototype circuit boards without milling away copper clad board material.  

Just as sometimes labs must use commercial software, it is likewise not expected that all lab hardware will become open source.  Some tolerances are too tight for the parts to be constructed by simple printers and some materials are not practical to print in the lab.  With all this in mind it is worthwhile to monitor the progress of open-source hardware such as the RepRap, Arduino, and the new RaspberryPi single board computer.  These tools may provide teaching support also as controlling and displaying data from classroom demonstrations is easier than ever and does not require the resolution/precision of research grade instruments.

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Posted in Education Opportunity, Electronics, Hardware, Open Source

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Laser Cave Profiling - The Beginning

Posted on December 22, 2011 | Leave a comment

Inspired by caving friend Nathan Williams photos of this technique I decided to try to duplicate his results and then write some great software.  The idea is to make profiles of cave tunnels known as cross sections very easily and accurately.  Cross sections are commonly sketched by a cave mapper by eye with a very rough scale.  Sometimes the passage is measured in height and width with a tape.

Here we use a motorized laser level and a DSLR camera to try to construct profiles.  After seeing Nathan's photos I got the laser level from Harbor Freight Tools (~$60) and used my Nikon D40X in a local Arkansas cave.

Today I just did a quick test about 100 ft. into the passage.  Below is a picture looking toward the level with flash so the tunnel profile can be seen.  Then I did a 20 second exposure with the level running and all lights off.  There was a small amount of light from the entrance, but negligible.

I then read the image into python, remove tripod reflections by subtracting the average of the blue and green channels from the red and then inverting the resulting monochrome image.  The result is seen below:

The big thing I need is the software to then produce a set of points that describe the profile so I can implement routines to compute area and make a pseudo 3-D model of the cave by stacking many closely spaced profiles.  I also tested the scale of the image by counting how many pixels wide the level appears and then determined the pixels/cm count to get the size of the tunnel.  This process will be improved and automated as the software develops.

I'm open to suggestions from cavers and numerical methods folks.  I have a contouring algorithm (Moore-Neighbor Tracing) coded, but it doesn't handle the breaks in the profile.  Any ideas on making it continuous and possibly minor smoothing? I plan to build a "T" shape device with 4 dim LEDs to provide a larger scale target.

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Posted in Caving, Electronics, Geology, Projects, Software

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Building a Fluxgate Magnetometer Part 2

Posted on September 1, 2011 | 4 comments

With school starting progress has slowed some, but currently most of the system is constructed.  First off the sense coil had to be finished.  The wire ends were coated in fingernail polish to keep the coil from slowly working undone and the entire setup was placed into a clear acrylic tube to protect it from wear.  The tube was stopped with standard rubber plugs and a computer power cord was soldered on for connection purposes.

With the function generator working it was time to amplify its ~100mV output to something that would induce a larger field via the driver coil.  Finally I decided to go with an operational amplifier (op-amp) design.  This requires both a positive and negative voltage source which is easily accomplished with two 9V batteries.  The signal generator will be run off a third battery because it is crucial that the two op-amp supply batteries remain at equal voltages.  My initial breadboard design (below) clipped the waveform badly (also below).  After some readjustments and gain fiddling a nice waveform was reached.  I built two amplifiers on a perf-board (one to amplify the signal to the driver coil and one to amplify the signal coming back from the sense coil).

It was also time to being thinking about a case/display.  Lexan seemed like the obvious choice so students can see inside.  I bought 2 sheets of lexan and nylon hardware to separate them.  Leaving the sides open allows easy oscilloscope probe access for recalibrating the amplifiers (I left little copper connections on the board for this purpose).  I designed the front control panel (not implemented yet) and drilled all the holes required.  Finally after mounting all the boards down to the lexan I powered up the amplifiers and they worked great (below)!

Next the bandpass filter needs to be nailed down.  I've worked on it some, but cannot get a satisfactory result to build up onto the last perf-board.  The signal that carries the information we are interested in is the 2nd harmonic of the 1kHz driver signal.  It will be weak so it is likely that the amplifier will need a bit of reworking and hopefully I can build some gain into the bandpass design (also op-amp).  The classic catch is increasing the Q of the filter, but killing the amplitude of the signal.  More to come...

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Posted in Education Opportunity, Electronics, Geophysics, Hardware, Projects

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Building a Fluxgate Magnetometer - Part 1 (and NASA)

Posted on August 18, 2011 | 2 comments

Today I want to discuss the first steps in building a simple fluxgate magnetometer for a classroom demonstrator.  Originally this post was going to be a wrap up of NASA work and the magnetometer would come later, but I'm still waiting on my presentation to clear export control so I can post it.  As soon as it does, I'll put it up along with a short article.

This semester I'll be the TA for 'Global Geophysics', mostly doing lab instruction/writing.  After some thought I decided that students need more hands-on classroom geophysics, which is difficult to do.  By its nature geophysics is an outdoor activity with normally expensive instruments.  The instruments are often viewed as a mysterious black box that spits out numbers used to make a map.  This must change.  With a proper understanding of the instruments students will better understand errors in the data, how to troubleshoot in the field, and know why certain hardware limits exist.

The concept of a fluxgate magnetometer is pretty simple.  Rather than go into detail I'll refer you to this wikipedia article.  This is mainly to chronicle the construction so others can reproduce this (assuming we get a working model).  My design came from a physics lab at Brown University.  The instructions were vague in parts and I'll be taking some liberties as we go along.  This first article will cover construction of the coil and the driver circuit.

The fluxgate coil consists of a driver coil surrounding a soft steel wire, and a secondary coil to pickup signal surrounding the primary coil.  First I took 16ga annealed steel wire from Lowes and cut it to about 1m long, cleaned it, and made it as straight as possible.  Afterwards I wrapped close to 2000 turns of 22ga magnet wire (Radio Shack #278-1345) tightly along its length.  This was then bent in half making a 'U' and that was wrapped with close to 1000 turns of 26ga magnet wire. I used large wire because it will be more durable and I used different gauge wire since the enamel insulation was a different color allowing students to easily see the windings.

That's all there is to the coil.  To increase durability I will probably clear coat the coil and place it into a small acrylic tube so its difficult to bend or break.  The next step is to build a driver for the primary coil.  The Brown lab used a function generator.  Currently I don't have one, nor have I found a suitable cheap unit.  This meant improvising, and luckily Velleman makes a signal generator kit that is just about right.  It operates at 1kHz (the desired frequency for this project) and produces sine, square, triangle, and integrator waves.  The kit was pretty easy to build in just about an hour and works well as seen by the oscilloscope output below, but frequency stability is not phenomenal (especially when then unit is cold).  

Next a few amplifiers need to be designed and built.  The signal generator kit cannot pull the load of the coil, so a simple +/- 9V system will probably do.  The output will also need some kind of amplification.  The lab I found also uses a bandpass filter.  Once the amplifiers are working it will be time to decide if this is necessary and if I want to use an oscilloscope and hardware filters, or an ADC and display the waveform on a computer projector using software filters.  

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Posted in Education Opportunity, Electronics, Geophysics, Hardware, Projects, Space

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Surviving a Crash - The Black Box Then and Now

Posted on January 13, 2011 | Leave a comment

After an airliner crashes there is a search for survivors (of which you have about a 1:100 chance of being among) and the search for the ever important in infamous 'black box'.  The black box records critical flight data that helps accident investigators determine what caused the crash and if there are problems with the airplane model that need to be corrected.  This was the case of the stripping jack screw in the tail of the MD-83 that caused the crash of Alaska Air 261 in 2000.  The black box has undergone many transformations over the years, but it has always had to be a durable machine that can preserve data through  the dramatic forces of a crash, water immersion, and inferno like fires of jet fuel and airframe materials.

Some of the earliest flight data recorders used photographic film rolls that had lines exposed on them by light reflected of sets of mirrors.  The mirrors were deflected different amounts according to aircraft parameters resulting in a 'strip chart' on the film.  This was easy to develop, but was only a one time use as the film had to be replaced after exposure.  The first data recorders just recorded a few simple channels of data and were common only on test flights due to their cost.

Later black boxes, like the one featured in the video below, used metal strips with the data scratched into the metal by a sharp stylus.  These records survived the fire and shock much better than film, but were still single use.  Keep in mind this is still all done with 'old fashioned' technology as there was no solid state memory in these days.  The next step was voice recording.  What were the pilots talking about before the crash?

Video on Analog Recorder

In the 1950's spy gadgets were the rage in the intelligence community and they required some of the same properties that aircraft flight data recorder designers desired: compact, durable, simple.  Wire recording was the answer.  Magnetically encode data on a spool of wire and use a ground based playback/decoding system.  It wasn't long before both the flight data and the cockpit voice data were being recorded on the same wire reel.  This reel could be erased and used again.

Modern flight data recorders and required to store at least 88 parameters by law (US) and they are solid state.  There are a few cases where the data has been unreadable to due destruction of the unit, but new units that propel themselves from the crash may solve that problem.  The new recorders also transmit a beacon signal making them easier to find for about a month.  Some of the smart units are even capable of observing when inputs are changing rapidly and collecting data more often as this is when things are likely to go wrong.

The purpose of this trip through the history of the flight data recorder was not only to show the evolution of a remarkable and very useful device, but to show how engineering problems can be solved without a microchip.  Are the recorders now better than those of the film days? Of course, but it required some out of the box thinking to build the mechanical recorders of the early days of aviation.

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Posted in Disaster, Education Opportunity, Electronics, Hardware

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