Archive for category development
It took quite a while to find the relatively safe radiation source. Thorium mantle from camping supply store is usually sold and used for camping gas lamps, but does emit some alpha radiation. Alpha is relatively safe, because it can hardly penetrate a sheet of paper or a plastic, so as long as I don’t eat or inhale it I should be fine.
Actually, the usual dosimeters cannot detect alpha, but can detect secondary gamma and beta emissions which happens when alpha strikes something. Therefore, I did not expect any precise measurement, but it was quite reassuring to get the numbers pretty close to the cheap Chinese dosimeter I’ve borrowed from a friend of mine.
Well, last week has shown the total lack of any radiation around my home. I have got pretty stable reading for a few days, which moved a little bit higher and lower, but mostly consisted of random background-level noise. The noise (~0.2 clicks per second), which should be expected from this kind of geiger tube at their respective age.
While this kind of picture looks quite dull and boring, I’m kind of cowardly reluctant of ordering any kind of radioactive materials to my home, so I’ve decided to take another approach. I’ve heard the granite stones are supposed to have 0.3-0.5uSv/hour levels, so probably tomorrow would be a good time to visit a stone sculpture factory nearby.
And for that purpose, here comes another board, this time without any USB connection, but equipped with a small LCD screen, so I can attach a pair of batteries and use it to see the results while away from home. Also I’ve got a cheap (relatively) Chinese dosimeter, so there’s a hope I can calibrate the output of my boards and don’t rely anymore on thumb-sucking approach when calculating CPM-to-uSv/h conversion rates.
Here’s the finished board connected to my computer. It works surprisingly well, reading about 20CPM on average — it might be cosmic rays or anything, because I’m too far from Fukushima and don’t really believe anything can be brought over here by wind. The power consumption from the USB bus is less than 10mA, which makes it safe to connect to any USB port, even to a laptop/notebook with a small and weak battery.
But even with this low power consumption, the naked board does not play quite well with bare hands — it still has enough voltage (about 400v) inside and is always ready to zap the finger. Still, the discharge current is very low — about 10uA, so it’s just a bit more annoying than static electricity discharge, like the one you get while getting off the sweater.
And here’s a fresh plot of today’s data. I have no idea what happened between 17:00 and 20:00, maybe my neighbours were microwaving the sausage or we had a solar flare, because it does not look like radiation at all. The radiation usually builds up pretty fast and then slowly decays over time, not the opposite, as seen on the picture. I shall check tomorrow’s graph to see if this phenomena will repeat itself again tomorrow.
The latest events in Japan are more or less related to the results of large earthquake on March, 11th and the radiation outbreak from the damaged units on Fukushima nuclear plant. I’m not equipped or willing to participate in the recovery efforts, but still can provide some help by building and sharing DIY Geiger counters, so people can put their minds at ease.
The design is not very original, first I saw the SparkFun Geiger counter (sold out for a few month already), then I have visited Techlib where I’ve learned a few things here and there about feeding the GM tubes with a proper voltage, and finally I’ve added a few pieces by myself.
The original prototype board was quite messy, but yesterday the first batch of PCBs has arrived and finally I could put all the pieces together.
The core part of the design is the Russian-made Geiger tube SI-3BG, which is not very sensitive, but still can provide good readings if left for a while (30sec-1min interval). The manual said the working voltage is 380-460V, which results in about 15-20 clicks per minute in the calm conditions without any radiation sources around.
The electronics design is quite stable and provides the stabilised high voltage about 400V with the power supply changing from 4V to 9V. The correct output voltage can be selected with the proper collection of Zener diodes and may range from 300V to 500V easily, or maybe even higher with the different transformer and diode/capacitor values.
The tubes I’ve got are from military arsenal, stored and kept in a cold dark place, so most of them work without a single problem. They are sensitive to gamma/beta radiation, well, mostly to the gamma, since beta cannot penetrate very far through the buildings and furnuture. But still, I think these tubes, while difficult to calibrate for a precise measurements, are quite adequate for my purpose — collect click data on the computer and see how it changes with the weather (the wind, and, especially, the rain).
Once in a while the particle or gamma ray enters the tube, and starts the discharge which can be seen as vertical streak on the oscilloscope or the impulse on the microprocessor input. Impulses are counted for a while and then periodically are sent to the computer over an USB connection. Currently I’m just watching the output and thinking about making a small application to build pretty graphs about changes in the background radiation levels around the place where I live.
I’ve got a broken Kenwood power supply today for a very low price, since the broken part was the “output” button, which enables the actual output. Fortunately I’ve got a few similar parts hanging around so I’ve spent about 10 minutes opening the case (10 screws just to hold the upper cover!) and disassembling the front panel, then about 15 minutes for the actual replacement and then 1.5 hours trying to put everything back, since the LEDs and buttons on the front panel did not want to go where they belong and occasionally decided to fall everywhere, on the table, on the floor.
Finally I’ve heard exciting “click” and I put it all together very quick wishing I would not have to open it again anytime soon. Nice power supply with three outputs — 8V, 18V and 36V, I can say. For a very-very low price.
Last year I’ve got WinMobile phone (Toshiba X02T) from SoftBank, also known as TG01 in the rest of the world. I did not like it very much, so basically it slept in the box unused. Recently I’ve noticed some new development and decided to give Android a try, since I really enjoy to run games and software on large 4.1″ screen.
If you don’t like to read the whole thread on XDA-dev, here’s a quick summary: buttons, screen and sound do work, anything wireless (WiFi, GPS, calls, SMS, network access) does not (yet). So, it’s a bit early to use this on everyday phone, but quite good enough to install software and play games.
Current version of Android cannot be flashed to device, but works from SD card instead. To start Android you have to boot Windows first, run Explorer, scroll the file list and click on the .exe file, which will unload Windows and load Linux/Android, which works until power off. Next time the power is on, Windows boots up again, which is good, since I don’t want to lose the warranty and official support.
Installation is quite simple. First you have to download the necessary software (there might be a new version, it’s a good idea to check the original thread for the new version if you are reading this after 2011.01.01). Then, I really loathe this step, you have to find 7zip to unpack the file, since the usual unzip will not work. After the file is unpacked, copy the “Android” folder to the SD card in your X02T phone. There should be some empty space left on the card, since additional files will be created when Android is run for the first time.
To run Android, first start the Explorer, go to SD card, open folder “Android” and run “clrcad.exe” (nothing visible will happen), then “haret.exe”. You should get the Linux boot screen.
It might take a few minutes, and possibly a reboot or two, since hardware is checked and some files are created, but finally there will be initial setup screen and Android home page. Once you got there, everything else is quite easy.
You may read the system log with: adb logcat
The battery indicator might not work, so it’s a good idea to keep the USB cable connected. However, since we need to run the programs from SD card, the USB mode should be changed to ActiveSync once the files are successfully copied to the SD card.
Also, it’s a good idea to watch the temperature of the phone back side to avoid overheating.
How to install the software?
Software installation can be done over USB link with ADB:
$ adb install AngryBirds_1.3.5.apk
* daemon not running. starting it now *
* daemon started successfully *
2546 KB/s (13466519 bytes in 5.165s)
- waiting for device -
By Rick Rogers, John Lombardo, Zigurd Mednieks, G. Blake Meike
Publisher: O’Reilly Media
Released: May 2009
Very nice “no-bullshit” introduction book. A little bit dated, because it’s based on SDK v1.1, and Android development went far ahead since 2009. Also, some of the examples don’t run ‘as is’ with the current SDK, but actually it’s not very important (who runs them anyway?), because the main point of this book — a very concise explanation of Android internals and development process. Explanation, which don’t dig very deep into the unnecessary details, but tells everything you should know to develop for Android. Well, maybe not everything, but just the right amount to get started, including the basic work-flow scenarios and solutions to common problems.
People with no computer background may find this book a bit difficult to read, because there’s no gentle introduction to every aspect of computing and programming, but for someone with even a little experience in computers who tries to jump into Android software development it’s a must have.