Thursday, March 17, 2011

APRS radiation monitoring

In the wake of the Japanese nuclear disaster there has been a surge of interest in interfacing Geiger counters to home weather stations so that radiation levels could be monitored via APRS. When you think about it, it seems a very good idea. Even if the measurements were not of lab grade accuracy, they would be good enough to show what was going on. It could avoid unnecessary panic - and equally make it impossible for officials to hide the existence of a radiation leak - if data from a network of amateur radiation monitoring stations worldwide was publicly available. This could be a real application to make APRS relevant even to the general public.

A standard for representing radiation measurements in APRS weather packets is being worked out as I write. The question is how to interface a radiation monitor to an APRS system and what hardware is needed to measure the radiation? Unfortunately, if not surprisingly, the final bid price of dosimeters on eBay has gone through the roof in the last couple of days. But in any case they all seem to be standalone instruments with no computer interface. I don't know if a homebrew device would be possible, given that calibration would be needed, but if someone could develop one I think it would be a popular project.

12 comments:

Lynn (D) said...

Even if you can't get them calibrated, if they are internally consistent, the label could read something like "relative radiation level". If the number is steady, all is the same as it was. If the number goes up, SOMETHING changed for the worse.

Julian said...

True. There is a radiation detector project here that looks easy and fun to build which would give relative indications of the radiation level. But if you wanted to record readings using APRS to create an independent global radiation level monitoring network you would need to use something that was calibrated at least to similar ball-park accuracy levels as cheap home weather stations.

LY2SS said...

Nice ideas, indeed!!!

John Zaruba Jr said...

Julian,

You might want to look here:

http://www.blackcatsystems.com/GM/GeigerCounters.html

Might be a starting point to acquire radiation measurements for APRS.

73,

John K2ZA

LY2SS said...

Interesting experiments (from the same link you gave above)
http://www.techlib.com/science/ion.html

Julian said...

Yes, this whole idea looks fascinating. I'm wondering if it would be possible to build something with a PIC circuit instead of a meter that could monitor ambient radiation levels accurately enough for amateur purposes.

LY2SS said...

Here's another approach to detect those particles. Probably this way would more friendly hi to digitize....
Here's exerpt

"Thus, a silicon PIN diode can be thought of as a solid-state equivalent to an ionization-chamber radiation detector"

http://www.carroll-ramsey.com/detect.htm

And practical approaches:
http://www.maxim-ic.com/app-notes/index.mvp/id/2236

http://www.techlib.com/area_50/enricosprojects.htm#Worlds%20Smallest

LY2SS said...

This one is useful too:
http://www.maxim-ic.com/products/ibutton/images/wideband.pdf

Julian said...

Good stuff! The "world's smallest" circuit looks interesting. I wonder how critical the components are, whether it could be made using the more commonly used JFET and general purpose transistors found in the average QRP junkbox?

LY2SS said...

It would seem offtopic at the first glance but this very interesting document contains I guess one of most sensitive/cheapest pin photodiode frontend. It mentions particles detection in page10.

http://sd-1.archive-host.com/membres/up/22679775843705539/PGPVUK.pdf

Someone has to start catching and counting particles!
AFAIR, I even have this same board laying in drawer and catching dust hihi!

Charlie said...

I have been wanting to do this since I learned that APRS could broadcast weather data and comments just because it was there. I got a Black Cat Systems GM-20 (http://www.blackcatsystems.com) way back and ran it at the office for some years until it was lost. When I got MT MacBook a couple of years ago I got another GM-10 and contributed my readings to the Black Cat Systems radiation map until the MacBook needed to be rebuilt. The GM-10 is a serial device and I have interfaced it with an Arduino to make LEDs flash.

My concept is that I would use the Arduino to split the signal so that it goes to the computer for constant logging and from there to the radiation map at whatever frequency it requires. The Arduino would also log and average the counts and output a data string to my radio every hour which would then be beaconed over APRS. Since I am not a programmer it is just a concept so far, and the fact that my 2m transmissions set off my smoke detector hasn't done anything to move the project along.

I had heard that the APRS weather specification has recently been extended to include radiation data but this site and a YouTube video are the closest I have come so far on how to make it work.

73 de KC2PED

Charlie said...

I just found this document which contains information on coding radiation levels for inclusion in an APRS weather beacon.
http://aprs.org/aprs12/weather-new.txt
Now how do you get that information from the Geiger counter into the radio. And for my purposes the radiation map wants uRad not the mSieverts that APRS wants.
Before I figured out it was my radio that was setting off the smoke detector my solution was to use a static comment message that I updated at mealtimes with the current average hourly count. I found that my average was constant enough that I could leave it set at 16.5