We teach the phone to count gamma rays or the second life of the old Soviet household dosimeter DBG-0.5B ...

Response to the DORA project

habrahabr.ru/post/132351
habrahabr.ru/post/143791



Once with friends we decided to visit a place whose name has been terrorizing the whole world for 27 years now and has become a household name for many - Chernobyl. Of course, in order not to wander into a place where you should not and not accidentally pick up anything extra during the trip - we decided to get elementary radiation detectors that would give elementary sounds that can be judged by the frequency of repetition where you are.

Interested please pass under habrakat.

')

How it all began

At the online auction aukro.ua I purchased a household dosimeter DBG-0.5B for 170 UAH (635 rubles or $ 21). Such a funny thing, one of the drawbacks of which was the lack of a display, instead of him on the dosimeter such a sticker was pasted.



The sticker shows a table by which one can roughly estimate the level of radiation by measuring the number of sounds made in a time of 10 seconds. There is also a toggle switch that allows you to switch to different ranges, thereby allowing you to read the signals even with high levels of radiation.
Range 1 - the sound is emitted when each 2nd gamma quantum is absorbed. Range 2 - the sound is emitted when each 16th gamma quantum is absorbed. Range 3 - the LED flashes when each 128 gamma quantum is absorbed.
But, as it turned out, there is another rather interesting way to count gamma quanta using a telephone.
On the AppStore there is an application called Geiger Bot
sites.google.com/site/geigerbot
it allows you to take readings from absolutely any geiger counter using a microphone or via a microphone cord (which is preferable because the application will pick up other sounds through the microphone, which will affect the measurement accuracy as a result)
On the website of the GeigetBot project, I found a circuit by which I soldered a cord with a mini-jack to a piezo emitter (tweeter)



The output was such a device. The soldering itself is extremely simple there, and I did it for speed and not very carefully, so I decided not to show the insides. If interested show.



The following is the connection and configuration of the dosimeter in the application GeigerBot
What really surprised me was the abundance of settings in the application. In my opinion, there are only two main settings:
1) The volume threshold is the level of the incoming signal at which the receipt of a quantum by the counter will be counted; The application has a special chart that displays the level of the current signal and the level line, according to which the meter counts a quantum. Alternatively, you can still trust the application and put this setting in the machine.



2) The conversion factor - perhaps the most important setting for a dosimeter, indicates how to convert signals into already known units (Sieverts, X-rays, etc.)



It is quite simple to calculate this coefficient according to the already existing table on the dosimeter, you just need to specify how many signals per second the dosimeter will give at a dose of equivalent radiation of 10 μSv / h. Taking into account the fact that my dosimeter in the first range emits 16 signals in 10 seconds, provided the dose of equivalent radiation is 1 µSv / h - it means it will give 1.6 signals in 1 second at a dose of 1 µSv / h and 16 signals per second at equivalent dose of 10 microSv / h.

Now we check the device in practice:

This is a stella at the entrance to the city of Pripyat, the background is 0.22 μSv / h, which is approximately equal to 22 μR / h.



At the entrance to the station



Radioactive moss in Pripyat, equivalent dose - 119 μR / h.



The photo was taken near the kindergarten, 12 kilometers from the station, in this place there is a drain where radioactive water flowed after the accident, now 109 micro-roentgens shine in this place





The last photo was taken by one of the guys who were with us on the tour. The foreigners in the group looked at the device with surprise and apprehension, and constantly asked what it was and where it came from.

Thanks to all. If you have questions, ask in the comments.

UPD As promised photo of entrails