Functional Eclipse Computer

August 8, 2017

I have progressed on the eclipse computer project past a prototype to something that mostly works. There a few minor bugs in the code, but it is usable as-is. I’ve got fixes for them, but need to test before committing. The system still doesn’t use its buzzer for an audible prompt, and I haven’t written anything yet to help take a sequence of pictures showing the progression of the eclipse. I may not get to that for a day or two to deal with travel related issues. I plan on taking it, and a bunch of camera gear, to the Nashville area to view the eclipse.Eclipse ComputerThe picture shows what is nearly the final hardware, but older software. This video shows the current software. The hardware changes between the two are all to help keep everything from moving around in the case, and to keep the barrel connector that supplies power to the upper breadboard close to the board. The connect was moving away from the board too easily and causing a reduction in the supplied voltage.

All of these problems were solved by applying solid copper wires in the right spots. I use solid copper with breadboards a lot because I can cut the wires to the length I need and the conductor is stiff enough to be inserted into the breadboard without tinning or the addition of some connector. I used a few more of these wires to hold down the barrel connector and to apply some pressure against the top of the case. It worked out quite well.

I changed the display from a 16×2 LCD to a 20×4 one just for the additional text. The video shows how I’ve made use of the space. The 20×4 display is a bit dark and needs a backlight to be readable unless it is in bright direct sunlight. The 16×2 display didn’t have this problem; it is more like a common digital watch display in how it handles light. I made and adjusted an automatic backlight control program that gets brightness measurements from a TSL2591 at its minimum gain setting and uses one of the Raspberry Pi’s PWM outputs. It seems to make the display readable enough in bright light and keeps it from being brighter than it needs to be most of the time. I’d rather have a 20×4 that is more like the 16×2, but I haven’t got the time.

I tested the computer running on 8 Eneloop NiMH 2000mAH batteries. For most of the test, the computer was indoors and used the minimum backlight setting. It recorded around 600mW power consumption under these conditions. In brighter light, power consumption got as high as 850mW. Working out a new times of totality can add about 400mW, but I wrote the code to limit how often that occurs.

The batteries kept the computer running so long that I couldn’t finish a battery life test in one day. The combined runtime before exhausting the battery charge was around 25 hours. That was much longer than I anticipated when I decided on 8 AAs. I’m still going to use 8 because I can, and the backlight will make the runtime a bit shorter, maybe 16 or 17 hours, about twice what I need. Also, a smaller battery pack would have more room to move about, and I already wrote low battery detection code based on 8 batteries in series.

I’ve got the Raspberry Pi Zero running Gentoo Linux. I made modifications to the configuration used by OpenRC to boot up the system so that it starts the program that provides information on the LCD and the separate backlight control program. A simple Bash script keeps re-running the software until it terminates without error, or the script is killed. No GUI is installed. I’m going to see if I can get it to set the clocks on my cameras, and bring up a network connection, when the corresponding device is plugged into USB. Nothing critical, but it would be nice. Hopefully plugging in a camera won’t cause it to reboot.

Eclipse Computer Prototype

July 30, 2017

I’m going to see the upcoming total solar eclipse on August 21, 2017 somewhere north of Nashville. I’d like to get some good photographs of the event, which makes anticipating when certain eclipse events will occur very helpful. For this purpose, I put together a custom computer system to provide me with some information about the eclipse based on my location.

The prototype eclipse computer

The prototype eclipse computer

The computer is based around a Raspberry Pi Zero running Gentoo Linux. I used a GPS receiver from Adafruit along with GPSD to query the location, and NTPD to synchronize the system’s clock with the atomic clocks of GPS. I also used a 16×2 LCD that is readable in bright light, and with the help of its backlight, is readable in the dark. To power it, I’m using Adafruit’s Verter product; it takes 3 to 12 volts in, and produces 5.2 volts to run everything. It makes for a flexible power supply that doesn’t require me to buy a special battery that I might not use much in the future. I plan to use 8 AA batteries.

The software figures out when totality, the part of the eclipse when the moon’s umbra blocks the sun from view, begins and ends using some data published by NASA. The data shows the irregular shape of the moon’s umbra projected onto the irregular shape of the Earth at one second intervals. Using this, I made the program search for which of the umbra shapes contains the location provided by GPSD. The resulting totality time information, plus the current time and location, cycle across the LCD. Its results don’t exactly match many of the interactive maps available online, but I think they may be using a simplified, maybe circular, umbra shape and may not account for the Earth’s terrain.

At present, the program doesn’t take any user input. I’m considering changing that, but I want it to be useful without input. I’m going to put it inside a sturdy case that is water resistant enough that it should survive a strong downpour, just in case I have to deal with less than ideal weather. The top of the case is transparent, so the current version of the system can be useful without opening the case.

What it doesn’t do right now is show when the very beginning and ending of the eclipse occurs. I’m having some trouble figuring out how to do this. I’d also like it to show the azimuth and elevation of the sun for the current time, the beginning and ending of the eclipse, and mid-totality. I hope to make a time-lapse video of the event, and want to keep the sun in the frame, but do not want to disturb the camera once it starts. I did make an attempt at computing the values based on an algorithm published by NOAA, but what I made doesn’t produce correct azimuth values. Unfortunately, that is the more important value of the two for this eclipse.

I have published my source code as two repositories on Github. The first is a library I wrote intended to provide a C++ happy high-level style interface to using low-level hardware. I called it DUDS, for Distributed Update of Data from Something. I’m not very good at names. The name shows what I’d like to do with the library in the future, but I’ve got to build up other functionality first. It is already useful for this eclipse computer, so I hurried a bit to publish the code.

The second repository is for the eclipse computer program. It also includes a program to test finding totality times that does not use DUDS, and takes longitude and latitude values from standard input.

I’ll be doing more development and testing for at least a couple weeks.

BBC, Voyager 1 is impressive

July 25, 2016

The BBC published an article with a paragraph that bugs me. It starts with:

The only spacecraft to have made it further than the planets, moons and asteroids of our solar system is Voyager 1.

To claim that Voyager 1 has traveled further away than all the asteroids is to claim that the Oort Cloud has none. Object 1996 PW suggests this is not the case. But if the comparison is limited to asteroids no further from the sun than the Kuiper belt, then Voyager 1 is only the farthest such spacecraft. Behind it is Voyager 2, Pioneer 10, and Pioneer 11. New Horizons hasn’t yet gotten past the Kuiper belt, but it’s on the way.

The paragraph continues:

At the time of writing, this plucky probe was 20,083,476,000 kilometres (12,479,293,426 miles) from Earth, travelling at some 17 kilometres per second. This sounds impressive until you remember that Voyager 1 was launched in 1977, is fitted with early ’70s scientific instruments, cameras and sensors and has been voyaging for almost 40 years.

How does a launch in 1977, and all that implies, make Voyager 1’s distance and velocity any less impressive? I don’t think it does at all.

Here is something that makes both Voyagers very impressive: they still function. Both spacecraft continue to make observations of the solar wind and are now seeing how it interacts with the wind beyond. The current prediction is that both will have enough electrical power to continue making observations and transmitting them until at least 2025, for almost fifty years of operation. How’s that for electronics and mechanical parts that haven’t been replaced or seen a mechanic in forty years, during which time they’ve been exposed to a good amount of ionizing radiation?

The Voyagers are very impressive feats of engineering. Operating for almost forty years only makes them more impressive. How many machines can do that without maintenance?

Weather Underground’s security issue

May 1, 2016
Malware download page

Image of the malware download page

I will often use the Weather Underground website to check the forecast, but I may start using the National Weather Service’s site instead. If I leave a tab on my web browser at work on the Weather Underground site, the image in this post will eventually result. The browser is an up-to-date Firefox without Adobe Flash running on Windows 7. It gets redirected to another website, always with a different domain name, and always with two seemingly random numbers in the path (visible in the image when large enough). The page looks like it is for downloading Adobe Flash, but isn’t on Adobe’s website. It sure stinks of malware. It may be coming from something like an advertisement that can sneak a redirection into the web page rather than content generated by Weather Underground, or maybe they have a more direct breach of security. Either way, I’m sure Weather Underground wouldn’t do this, but it is still annoying.

The issue has occurred five times over more than a month, maybe two, on the same computer. I did attempt to inform them of the issue, but I haven’t seen any indication that anyone took it seriously. It has happened twice since then.

At home, I run Firefox on Linux and do have Flash installed, although I usually have it disabled. The issue never happens there. I haven’t yet tried on another system without Flash, but suspect that may trigger the redirection.

What this doesn’t answer is what happens when this malware could redirect a browser, but finds one with Flash installed and enabled instead. I also didn’t accept this download. I’m not employed to do security research, and the IT department is quite distant.

A call to Comcast

December 31, 2015

I had reason to call Comcast today. It went something like this:

COM: You’ve reached Comcast customer service. This call may be monitored. Someone will answer whenever they get around to it, so wait. More blah . . .

COM: Is this you address?

ME: Yes.

COM: There is an upcoming fight. Would you like to hear about it?

ME: No.

COM: Please say yes or no.

ME: No.

COM: Two grown men will beat the crap out of each other for violent entertainment that costs money to watch. Do you want to pay for it?

ME: [Hang up since no means yes]

The only fight I’d like to see is between Comcast customers, armed with clown hammers, and their head of customer service. It would be the most brutal clown hammer fight ever.

I wonder how many programs I’ll have to pay for before I reach a person. Sounds like another reason to cancel service, but what little competition there is tends to be no better. Thanks FCC!

Useless toilet repair parts

November 22, 2015

It is a good thing that I didn’t leave earlier for Thanksgiving. I heard an odd sound from my bathroom today, followed by the sound of water spilling on the floor. I quickly found the problem and stopped the leak. A connector for the water supply to a toilet had fractured, allowing water from the incoming hose to escape.

Toilet water inlet parts on dirty old floor

In the image above is the hose with the fractured white connector, although the damage isn’t visible. I found that I have a replacement part from a toilet repair kit that I bought years ago (bottom left), but I can’t figure out how to remove the broken part. It seems like I would need to break the metal collar on the hose. I don’t know how to do that without breaking the hose, but even if I could, I would need a replacement for that, too. After searching the web for a while, it seems that the connector part is not replaceable; the whole hose needs to be replaced.

That begs the question: why was that replacement part included in the repair kit that I got? What am I missing?

Boost C++ library and the end of the world

November 8, 2015

While working on some C++ code, I made a mistake and got this error:

ERROR: Throw location unknown (consider using BOOST_THROW_EXCEPTION)
Dynamic exception type: boost::exception_detail::clone_impl
<boost::exception_detail::error_info_injector<boost::gregorian::bad_year> >
std::exception::what: Year is out of valid range: 1400..10000

I find two things rather interesting here. The first is that the Boost date_time library isn’t using the Boost exception library. The second is that the date_time library has defined the year 10000 as the last in the Gregorian calendar.

Based on this, I predict that the end of the year 10000 will be the end of the world. Using the Boost libraries to make end-of-the-world predictions should work about as well as using the Bible, right? The end is nigh!

Sigma 18-35mm f/1.8 autofocus is good

October 5, 2015

Just a quick follow-up to a previous post. I got a lot of use out of my Canon mount Sigma 18-35mm f/1.8 lens with upgraded firmware when my nephew Liam and my brother Jason came for a visit to Central Florida. I previously thought the autofocus wasn’t as good as it is with Canon lenses, but I was wrong. It is about as good as my Canon EF 85mm f/1.8 on the same camera, an EOS 70D. Neither lens gave me perfect autofocus, but I take extra pictures to minimize that trouble. I also used the continuous autofocus feature (Canon calls it “AI Servo” because marketing I suppose) a lot in an attempt to keep up with a four year old. The focus quality seems worse in low light than compared with focusing just once; this seems to be an issue with the camera. Overall, I’m really happy with the lens.

Potential change of NRC radiation exposure standards is something to care about

September 27, 2015

The United States Nuclear Regulatory Commission (NRC) is considering a change to the standards for allowable exposure to ionizing radiation. If you live in the US, this is something to care about since these standards affect what certain operations are normally allowed to put into the environment, and what is considered safe for the general public rather than just workers at such facilities as nuclear power plants. The NRC is taking public comments on the matter until November 19, 2015.

The standards for exposure start with a model to describe the health risk of a given exposure to ionizing radiation. The model used currently by the NRC and all other regulatory bodies in the world is known as the Linear No Threshold (LNT) model. This model has the premise that any exposure is bad, and the risk to health grows proportionally with the exposure. The alternative being considered is the radiation hormesis model. This model supposes that a small exposure has a positive effect on health, but too large an exposure is detrimental. After researching this over the course of a week and a half, I have decided that this isn’t a good change, but may not be as bad as it sounds.

Scientific research into how ionizing radiation affects the human body has produced some results that support the LNT model and some that support hormesis. There doesn’t seem to be a scientific consensus on the matter, so I haven’t found a good explanation for the discrepancies. There are scientists who argue passionately in support of one conclusion or the other, and they don’t always acknowledge evidence that contradicts their position. This leaves me uncertain about which model is closer to correct.

The NRC is responsible for establishing regulations that keep workers and the public safe. Since there is research supporting both models, the one that assigns greater risk to radiation exposure should be the one used. It will error more on the side of caution and suggest limits closer to the natural environment. The model that does this is LNT, the one currently in use.

The NRC was also asked in the petitions to raise the acceptable exposure limit for the general public to be the same as workers who deal with ionizing radiation on the job, such as people who work at nuclear power plants. Given that there is research supporting LNT, that people have varying susceptibility to cancer, and that some people undergo radiation therapy that may increase their susceptibility, this seems like a change that is a risky experiment in proving hormesis. Even if LNT was not well supported and hormesis was, it is not clear to me that the petitioners have considered people who may be more susceptible or vulnerable to cancer from radiation exposure.

My research first led me to the website of Dr. Ian Fairlie, a scientist who has published several papers on the health effects of radiation in peer reviewed journals. He wrote a post specifically on the matter before the NRC. There, he mentions several peer reviewed papers to support his case, such as Leuraud et al 2015. That one found Leukemia was more common in radiation monitored workers. It is an important finding because such workers are exposed to low, but higher than background, amounts of ionizing radiation over long periods of time. The finding directly supports the LNT model. It is also interesting since the work was partly supported by the US government, including funding and researchers from the Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, and the Department of Health and Human Services.

However, Dr. Fairlie also mentions a paper on the rates of childhood Leukemia near nuclear power plants in Germany (Kaatsch et al, 2008). While it does show that childhood Leukemia is more than twice as common within 5km of the power plants, it does not establish the cause. The authors concluded that radiation may have little to do with it. The paper states that the natural background radiation over the areas studied is much greater than that released by the power plants, but it seems neither was measured for the study. It also mentions other possible causes of Leukemia; there is some evidence of a cause by infection (Alexander et al, 1998). This may seem to question the results of the Leuraud et al study, but that one had the advantage of data from personal dosimeters while the Kaatsch et al study does not. In any case, it looks like Kaatsch et al really isn’t good evidence in support of, or contrary to, the LNT model.

From there, my research jumped to the petition of Dr. Carol Marcus to the NRC that seems to have started the process of reconsidering LNT and considering hormesis as a replacement. In it, Dr. Marcus writes, “There has never been scientifically valid support for this LNT hypothesis”. To support this statement, she mentions only one report (“Evaluation of the Linear-Nonthreshold Dose-Response Model for Ionizing Radiation”, from the National Council on Radiation Protection and Measurements, 2001, executive summary link) on the matter and presents an attack on it by Dr. Zbigniew Jaworowski and Dr. Michael Waligórski. This is evidently supposed to discredit all evidence and research that is consistent with LNT rather than hormesis, but it doesn’t refute the kind of empirical data seen in the Leuraud et al study, and likely others as well.

The existence of good peer reviewed science supporting LNT makes Dr. Marcus’s claim of no valid scientific support for LNT false. However, there is also such science in support of hormesis, so she might yet be proven to be supporting the correct model. I do not think the NRC should be making radiation monitored workers and the general public accept a potentially greater risk without a scientific consensus on the matter. I do not think it is proper even if a little more radiation might decrease the risk of so called solid cancers, as claimed by Dr. Marcus in the petition, if it also increases the risk of Leukemia. I think further research should be done on the effects of a total lack of ionizing radiation, including natural background radiation. This could be very helpful in better understanding the biological response to radiation.

In researching all this, I also looked into the background of the scientists. The really interesting one was hormesis proponent Dr. Jaworowski. In addition to publishing science on the effects of radiation in peer reviewed journals, he also published articles about or related to global warming. He claimed people should be more worried about an upcoming ice age, but published many of these articles without peer review, and they have been largely discredited. So far as I can tell, he was not a climatologist. He had a number of articles published in 21st Century Science and Technology, and Executive Intelligence Review; both are publications with ties to Lyndon LaRouche, which brings in some very strange and unusual politics.

XPS 13 Developer Edition (2015): Rushed

July 29, 2015

Dell’s XPS 13 Developer Edition from 2015 has some nice hardware, but it was rushed to market. The machine isn’t usable as delivered. Either no QA testing was done, or an impossible deadline was imposed. I’m pretty sure it was a deadline. It took the managers a while to realize this is a problem, but they finally decided to act by no longer selling it until they fix it. Someone with basic Linux sysadmin skills and some time to install the various fixes can get it working quite well so long as they aren’t a fast typist; key repeats are only mostly fixed as of now. With the fixes, I find it can still fail to resume from suspend, but it doesn’t happen often and leaves nothing logged to indicate the problem. Overall, I like the machine more than I should.

I went for a model with the 1920×1080 display and no touchscreen because I don’t like glossy displays. I do like resolution, and this is plenty for the small size. I’ll be using font anti-aliasing for a while longer; probably could turn that off with the higher resolution model.

Dell shipped it in a cardboard shipping box that distinguished itself by including a plastic handle so it can be carried around like a briefcase. Inside that is the power supply and cable, and a black box. A very nice looking black box. Inside that is the XPS 13 with foam above and a plastic tray below that is very well fitted. Clearly a lot of though went into this, more than I have managed to convey. Underneath the computer is a folded paper on using MS Windows. I know the Developer Edition uses the same hardware as the XPS 13 with Windows pre-installed, but I didn’t expect it would include the same, but useless, documentation. Not a big deal, but maybe a harbinger.

When turned on, the XPS 13 quickly boots and brings up a legal document. Fun stuff. After a short delay, although long enough that I thought it would let me read the document, a video starts playing full-screen. The video cannot be stopped, and trying to switch away doesn’t work. Alt-tab brings up the window switching menu, but it doesn’t switch. I also couldn’t mute the audio or change the volume; I’m used to pressing two keys to get the functions like volume control, but only one was required. I eventually figured that out, but it did make the compulsory video rather annoying. What made it obnoxious was that it was just an animation of logos zooming about put to music that meant nothing.

With the video done, I got back to reading the legalese. I needed to scroll the text, so I got to use the mouse. It occasionally quit working for two seconds or so before accepting more input. There is a fix for this from Dell, but not on the part of their website for supporting purchased products. That is, if you were to purchase a XPS 13 Developer Edition, log into your account on Dell’s site, find the item you bought, and try to download fixes, then you won’t find them. The fixes are on Dell’s website, just not there. It is apparently reserved for Windows related fixes and system firmware, aka BIOS. A search engine is the best way to find the Developer Edition fixes. Once applied, the mouse no longer ignores input, but occasionally when trying to scroll with it, the system will respond like alt-tab is down and cycles through the windows super fast. I have no idea how to reproduce the issue. It hasn’t happened in the last couple of weeks, but I’m not sure it won’t happen again.

Soon after that, I got to try typing. It regularly repeated key inputs until another key was pressed. This didn’t take fast typing to observe. A BIOS update mostly corrects it, but people who type really fast report that the change only mitigates the problem. The issue affects Windows as well. Considering that keyboards are common computer hardware that have generally worked well for decades, and that Dell botched it in 2015, it is amazing the rest of the hardware came out as well as it did. The group within Dell that put Ubuntu Linux on the XPS 13 clearly had a hard time dealing with this hardware.

After this, it was time to update the installed software. The Ubuntu Software Updater ran until it got to grub, then seemed to hang on the update while still responding to user input. After waiting half an hour, I killed it and what seemed to be a related process that was eating processor time. Then I used apt-get from a shell and ran whatever command it told me to run when it complained about some problem. Since then, updates have worked correctly. I have to wonder if an uncorrected hung update would render the system unbootable.

Following that, the system needed updates for the graphics to resume reliably from suspend. I still have an occasional issue with it, but matters greatly improved. A remaining issue is how the screen brightness automatically adjusts: it darkens for a mostly dark frame, brightens for a bright frame, and offers no user configurability at all. I was worried this would be an issue for working with photographs, but the screen’s limited color gamut, at least compared to another display I have, has proven a much bigger issue. I just have to learn to avoid over saturating the color.

Other than that is an occasional crash for no apparent reason. I’ve had it happen shortly after booting the computer and starting to browse the web. It was occurring twice a week, but hasn’t happened in a couple weeks or so; maybe something was fixed.

The XPS 13 Developer Edition was in no condition to ship. Asus did a much better job with their Eee PC line; they might have been limited by their Linux distribution, but they worked fine right out of the box. Still, I’d rather not buy a computer with Windows pre-installed, and I like that Dell is going through some effort to support Linux, including getting patches into the mainline kernel to improve hardware support. I’m guessing the XPS 13 issues were unexpectedly time consuming to fix and management didn’t want to wait.


False Steps

The Space Race as it might have been

keithlugcom.wordpress.com/

You Control The Action!

High Frontier

the space colony simulation game

Simple Climate

Straightforwardly explaining climate change, so you can read, react and then get on with your life.