Step 1: The Geiger Counter
I built my geiger counter 20 years ago from scratch. I incorporated a optocoupler as the output. Every time a particle is detected, a pulse is made and the counts can be monitored by a PC. A search on the internet will show you how to make your own or you can get a kit or finished product. What is needed is an output that can drive an optocoupler.
Step 2: Free Counter Software
To monitor the counter you need software that will count and log the readings. I always welcome free software if it is good and useful. A search on the internet found a program called "Digital Geiger Counter" from Images Scientific Instruments. The program will log and plot the data in real time. The software is not a demo and is not limited. The company also provide counters and kits for those who don't want to build from scratch like I did.
Step 3: The Interface
To get the counts to the software, an interface is needed. This interface (PDF) will count pulses during each 1 sec intervals and pass them along to the software through the PC serial port. I connected my Acer netbook with a Airlink 101 USB dongle to the RS232 output of the interface. The interface converts count per second to 9600 baud serial with a Picaxe microcontroller. The program is only a few lines of code and is shown on the drawing. You can get a Picaxe at Sparkfun and the free complier at Revolution Education.
The interface can be built on a piece of perfboard. I made some PC boards for use with the picaxe and used one of them.
Step 4: Streaming at Ustream
Step 5: My Ustream Channel
I have my geiger counter running on-line at Ustream. There you can see in real-time the levels of background radiation. My station may or may not be on 24/7. I like to use my Acer Aspire One for other things besides streaming.
Below is a screen shot at my Ustream channel.