DIY :: Geiger counter, now with LCD display

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.


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DIY :: Geiger counter with USB connection, part II

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.



DIY :: Geiger counter with USB connection

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.


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HOWTO :: Archos 70 ddms/adb connection

It’s fun to play with Archos 70, but eventually comes the development time. Since Archos 70 is not officially supported by Google, “adb devices” gives empty list and “ddms” does not see it either.

1. First step is to find out the maker/model code.

$ lsusb
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 013: ID 0e79:1411 Archos, Inc.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

2. I thought “android update adb” will get the job done, but got no results here. Then I’ve just manually added the maker code to .android/adb_usb.ini file.

$ nano .android/adb_usb.ini
# USE 'android update adb' TO GENERATE.

It’s a good idea to kill adb server at first. Then “adb devices” starts to see the tablet, but could not access it propely.

$ adb kill-server
$ adb devices
List of devices attached
???????????? no permissions

3. It’s time to assign proper permissions for the USB device

$ sudo nano /etc/udev/rules.d/53-android.rules
SUBSYSTEM=="usb", SYSFS{idVendor}=="0E79", MODE="0666"

Well, this time everything works just fine:

$ adb devices
List of devices attached
A70-6A920022-9FF80000-0160C5C6-14015009 device

And I could even snap a screen capture with “ddms”.

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Archos 70 :: first impressions

Yesterday I’ve got 7″ Archos 70 tablet from HK for about 20.000yen. They also had 10″ model with 1024×600 screen, but I already have an iPad and was looking for something a tad smaller. The delivery took about 3 days by FedEx.

Archos 70 has Android 2.2 (Froyo) installed, along with the WiFi (802.11/b-g-n) support. After asking all the usual questions about time zone and keyboard, it connected to the internet and offered to download and install the fresh firmware. Firmware installation does not run on the battery power and requires the external power supply, which it quite smart. There are Japanese/Chinese screen interface options, but since I’ve chosen English as the default language, I’ve got only european keyboards available.

Screen resolution is 800×480, like on my HTC Desire, but the actual size is about 3 times bigger, which makes it very easy to see every small detail on the Google Maps. 8Gb are installed (16Gb for 10″ model) as internal memory for movies and music, and less than hundred megabytes are available on the system partition for the software installations. Since there’s also an microSD slot available, the memory size it not very important and I can easily add up to 32Gb more. Upper panel has the microphone, VGA-quality video cam for video calls over internet and two speakers with reasonable good sound, especially considering their size.

On the side panel there are 1)microUSB connector, 2)microSD slot, 3)headphone jack, 4)microHDMI connector and 5)power supply connector.

It’s a bit unexpected, Archos 70 battery cannot be charged over an USB cable. Probably it’s somehow related to the USB-host support for external HDD and other devices. Still, the universal (100-240V) power supply is included and has support for most wall outlets over the world — Japanese, European and American plugs are included.

Because of some political issues (absence of GPS/phone calls support?) the Archos 70 did not get the Google’s blessing and does not have Android Market support right from the box. However, Google Market and Gmail/Latitute/other software can be downloaded from the internet and installed separately. Soon after that I’ve got fresh Andry Birds running without any problems.

Internet support is outstanding, Archos 70 can see twice as many AP from my apartment, compared to the iPad. Application download speed is great. Youtube works very smoothly. All my home servers and computers were detected automatically and I can easily (unlike the iPad) browse and watch movies and listen to the music. Even the 720p movies work totally flawlessly over the WiFi connection. Most video/audio formats are suported just from the box, and new codecs can be downloaded from the Archos web-site.

Tablet body is made from plastic, very thin and very light — I can easily hold it with one hand for hours. HDMI connector allows to bring video to the large TV screen, and not only video but the other screen contents — icons and running software too.

GPS is missing together with the phone support. However, Archos 70 can find it’s location based on the WiFi spots around — it has marked my apartment on the map within 100m of the actual location. I understand it might not work everywhere, but for the people with wireless network at home and at work, who even eat only where they have WiFi access it should work reasonably well.

The screen is bright enough for indoor use. Viewing angle it not very wide, but it’s not a TV set — I can always align it the way I like. Before the screen turns off to sleep, it dims a little at first — a very nice feature, especially when reading news, a few seconds are enough to touch the screen and prevent it from sleeping. There’s also “deep sleep” mode which not only slows down the processor and turns the screen off, but stops the device totally — even alarm clocks and background tasks go down. Can be a great battery saver, though I haven’t tried this mode yet.

All in all, if you are looking for an Angry Birds-compatible tablet, which can be used to browse internet and to watch movies on the couch, I’d recommend this (or the 10″ model, if you are not going to put it in the pocket and try to use it somewhere else or bring along for a stroll).


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KENWOOD :: button replacement

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.


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iPad :: Angry Birds Pad, actually

It’s about one month since I’ve got an iPad, which is twice the screen size and half the price of HTC Desire. The original purpose was to take the game load off my phone, and everything went perfectly as planned. “Angry Birds” (all flavours) and “Cut the Rope” are the games of the choice for the children. With occasional RSS reading in the spare time for the parents.

Besides gaming and reading the news, there’s not much possible, though. Web browsing is extremely slow even on WiFi. Applications are a bit “peculiar” for everyday use. Still, you can’t beat the $350 price for 10″ tablet with Angry Birds support.


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HTC Desire :: aftermarket 3000mAh battery

I’ve ordered this a few weeks ago for $15 on ebay and delivery from Singapore definitely took its time. Today it has finally arrived and I can tell this battery looks really mean with all the 3000mAh power hidden under the hood — it’s almost twice as thick as the regular one and does require the special back cover to accomodate this thickness (no worries, the new cover was included in the package). Now it’s time to recharge and I wonder how long it might take with the battery of this size.



iPad :: first impressions

Recently Apple has introduced new iPad2 and the iPad prices plunged overnight. I’m not big fan of Apple or their products, but given the opportunity to get a 10″ tablet brand new for $300, I just could not resist the temptation. After all, I need to have a reference point for comparison with Android.

Well, the very first impressions were quite unexpected. I’ve never had a thought that after I have recharged the battery and turned the iPad for the first time I’d be unable to do anything. Brand new iPad shows “connect to iTunes” picture, which beautifully rotates with a nice smooth animation when I turn the tablet upside down, but that’s pretty much it. I can turn power off and back on to see the same picture. Nothing else happens. Nothing at all. I wonder how the people use iPad if they don’t have a computer. Or if they have a Linux desktop, which does not support iTunes.


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HOWTO :: repack and sign ROM image update .zip files

DISCLAIMER: I don’t invent anything new here, but just summarise things I’ve read across different forums and web sites. I did not write any software mentioned here, but only copy the files and made them available in one easy to access place. I use the procedure described here to create ROM images I flash to my HTC Desire phone, and so far it worked for me perfectly. However I do not guarantee it will work on your system with your files and your phone — use it at your own risk and assume all responsibility. REFLASHING YOUR PHONE MIGHT GET IT BRICKED AND MIGHT VOID YOUR WARRANTY.


To be able to follow this explanation you will need the basic understanding of the command line, be able to enter commands with the parameters, to walk from one folder to another, to compile programs and to run the resulting binaries. To run Java programs you’ll need Java SE runtime installed. To compress and uncompress files you’ll need “zip” program or something similar.

Your phone should be rooted beforehand or allow the installation of custom ROMs.

The Outline

The process of creating your own ROM update file is not very complicated. Basically it consists of three steps:

  1. Download and unpack the image you like
  2. Make the necessary changes
  3. Pack and sign the .zip file

The update can contain as much as the full system + boot + radio + recovery + extras, which completely overwrites everything you have in your phone, or as little as single .apk file if you want to make just small changes.

Download and unpack

There are plenty of images available on the internet, it’s in your best interest to find the one as much similar to what you need to reduce the necessary changes and introduce as few problems as possible. There are three types of images you may use:

  1. RUU images (.exe)
  2. OTA images (.zip)
  3. 3rd party .zip images

RUU images contain full system, including radio, system, boot and the whole nine yards. However you’ll need to unpack .exe file into .zip file before doing anything useful. I have explanation how to extract the .zip file in Linux but if you use Windows or MacOS your procedure might be different.

OTA images usually contain only the difference between the previous software version and the current one. Therefore you’ll need the previous software as RUU/.zip file with the exact version, and be familiar with bspatch utilty to apply patches, which is quite tedious process. I don’t usually use OTA files if there are any other options available.

.zip images are the easiest to work with, just unpack with your zip archiver to the folder you like.

If you have started with RUU image, you’ll have system.img, boot.img and radio.img files. System image can be further unpacked with unyaffs (requires compilation) to another folder, usually “system/”. Boot image can be unpacked with the perl script (requires perl to be installed on your computer) also to another folder, usually “boot/”. Radio images cannot be unpacked and are better to be left alone.

Make the changes

Most of the changes are done to the system image, which contains all software and data files visible on the phone. Boot image should be changed only if you have deep linux knowledge to modify linux kernel and related matters.

If you have unpacked system image and made some changes, the system.img file is supposed to be moved somewhere else, so it’s not used anymore. Same with the boot.img file. All other files (hboot, recovery) are usually not used, because they might lead back to unrooting the phone and should be deleted or moved as well.

If you have based your work on RUU file, you’ll have to create META-INF folder with the correct information and update scripts inside. If you have unpacked someone’s .zip, the META-INF folder should be already present. Update script might mention some files in the update, so if you have removed (or added new) files, the update script should be amended to reflect those changes. Please, get a few images from different developers and try to understand the correct internal structure.

Pack and sign .zip file

Once you’ve made all the changes, you may change to the folder where you extracted all files, it might now contain .img files, like boot.img and radio.img as well as folders, like “system/”. Zip everything together with the command:

zip -r9 *

-r9 tells the program to collect files recursively and use the maximum compression. If you omit “r”, the subfolders will not be included (bad, bad idea!), if you omit “9″ nothing bad will happens, but resulting file might be about 1% larger.

To sign zipped file you should download (requires Java), there are three files inside:

  • SignApk.jar is a tool included with the Android platform source bundle.
  • testkey.pk8 is the private key that is compatible with the rooted recovery image
  • testkey.x509.pem is the corresponding certificate/public key

and the signing command looks like this:

java -jar signapk.jar testkey.x509.pem testkey.pk8 [] [] can be copied to the phone and installed using the traditional recovery procedure. Personally I’d recommend “ClockworkMod Recovery” from Koush and Paul O’Brien, but I’m not sure if it is available for your phone.


While the actual creation of your own ROM update file is not very complicated, the devil is in the changes you make. Most ROM updates fail at first try, please, have a fresh nandroid backup ready at all times.

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