Amateur radiation sensor network
From HvWiki
Contents |
This project is stuck until some new members join
Harry: An idea I've had for a long time would be a chain of international amateur radiation monitoring stations. Each would use identical, inexpensive equipment mounted so far as possible in the same way (or according to a rule) The output from each station could be displayed in real time on a single web site, both as comparative live graphs one above another, and perhaps superimposed on a global map if there were enough stations to make it worthwhile.
Ideas
Record any interesting ideas here...
Radiation vs weather
Note from aonomus: Bjorn and Harry, I found this link: http://www.vk2zay.net/article/220 The guy noted that radiation increased during rainfall (he hypothesized due to radon daughter products coming down with the rain. Hope it helps.
- Bjorn: That is very useful. It enforces my feeling that it would probably be a good idea to have other types of sensors too to see if there are any correlations.
Radiation from space
With many detectors placed at different places it is possible to filter away local variations. Global events that affect many sensors at the same time are likely to originate from space. The shielding of the earth combined with the rotation should give useful directional information.
Prototype
- ET-BASE ARM2103 microcontroller with RS-232 port
- PC running Sensorlink 1.0
- Reference design with Geiger-Mueller type GM 16/60B glass gamma-beta G-M tube
Radiation sensor
The simplest way to get the project going is to use relativistic measurements, rather than absolute measurements in microsieverts/hr.
What I mean is this: unless all stations use standardized equipment mounted according to a protocol (which would be too expensive and complicated to attract many beginners) then the best way for each station to present its data would be by a graph showing the average number of counts at that station over the previous month/3 months, compared with the current count of the day or week. This is what I mean by relativistic measurement.
100 µs TTL pulses to the microcontroller
Interface to the PC
- A microcontroller counts the events from the sensor and buffers them if needed.
- Directly to the serial port. The pulse must be negative and idle must be positive. See RS-232 for valid voltages. The length of the pulse must be longer than one start bit and shorter than 9 start bits. In some cases 0 V instead of negative will work. The length of the start bit is 1/baudrate seconds. So a 100 µs pulse requires a baud rate of less than 9600 baud. The shortest time between each pulse is larger than 10 times the length of the start bit. The PC will ignore the content of the received byte and just count the number of bytes received per second.
Possible options
- ET-BASE ARM2103 microcontroller with RS-232 port
- PICAXE
- PIC (Does not have a bootloader which causes complications for the user)
- Directly to an Ethernet router that is connected to the internet. It is possible to send UDP packets using the SPI port at 20 MHz. The main purpose is to save power by letting the PC stay off when it is not in other use.
PC software - Sensor Link 1.0
The input is RS-232. For USB only machines, use a USB to RS-232 adapter.
- Number of events for every hour (The microcontroller buffers while the PC is turned off)
- One byte per event (The PC must be turned on at all times)
Prototype uses Visual Basic Express 2008
Dim client As WebClient = New WebClient()
client.Headers.Add("Content-Type", "application/x-www-form-urlencoded")
client.UploadData(URL & "net2.php", "POST", encoding.GetBytes("data=" & text))
Protocols
Between Microcontroller and PC
Format of packet from the microcontroller: 'CTTTTNNNN' Reply from the PC: 'A' If the microcontroller receives '?' from the PC it replies with the current count 'C0000NNNN' If the microcontroller receives 'A' from the PC it removes the last sent count from the FIFO.
From PC to server
HTTP POST is used because it passes through firewalls and routers without any configuration needed by the user.
POST variables
- ID - 32 bit unsigned decimal number to identify the sensor
- Type - Normal, Transient
- Value - The decimal value returned
- Absolute - True or False
- Unit - The unit of the absolute measurement (Use SI)
- Time - UTC time of measurement in 24 hour ISO 8601 format - YYYY-MM-DD HH:MM:SS.SSSZ [1]
- Position - ISO 6709
- Stationary - True or False
From microcontroller to server
UDP over Ethernet through ADSL router
Web software
PHP script on the server that receives the POST data.
<?
$data = $_POST['data'];
$f = fopen("data2.txt","a");
fputs($f,$data . "\n");
fclose($f);
?>
Use Google maps [2] to display the sensors on a world map.
Radio links
In some cases a radio link may be needed for example to get a sensor into the sea.
