Radiation detector, help needed!

98 thoughts on “Radiation detector, help needed!”

1. Hello,

   We will be glad to help as well if we can. The problem is getting components (we ordered a LNI 712which is on its way) but in the meantime regarding power supply you could test this circuit.
   http://www.maxim-ic.com/app-notes/index.mvp/id/3757
   You can also find a complete circuit schematic here (See page 49):

   http://www.swinburne.edu.my/docs/library/epe/200703_mar.pdf

   which is a corrected circuit diagram for the one published the month before:

   http://www.swinburne.edu.my/docs/library/epe/200703_mar.pdf
   See complete description and circuit starting page 11

2. Something like This

   http://www.nukalert.com/

   Simple to use, and most importantly, calibrated. Buy one, tear it apart, see what makes it tick.

   http://www.nukalert.com/technical.htm has a good basic description of the detector, as well as the rest of the device.

3. completely agree with William. I wonder if it needs an instrumentation amplifier. The output can be an integrated voltage which is somehow proportional to the number of counts. But that can be difficult to calibrate, due to temperature dependency of the components and ageing of the sensor (pin diode or FET). I would suggest a second output which gives one pulse/count, that would not require calibration. Further, the circuit must be as discrete as possible, to make it radiation resistant.

4. Advise you focus entirely on a simple CALIBRATED sensor board with 2-wire interface. Don’t worry about the bells and whistles…. The rest of us can take care of the fancy stuff. Manufacture and distribute in concert with the usual suspects (LadyAda, SparkFun, etc.)

5. AndyH,
   The noise is thermal, it comes from the impurities in the silicon. That patent US4394676 refers to PN diodes as having a low impedance, which is correct, thats why PIN junction would be better. That patent’s invention is based on CdTe solar cells, I suppose Cd and Te are easier to purify than Si. Still I would go for high reproducibility, which is given by commercial diodes, instead of solar cells. You cannot use large area solar cells anyway due to the large capacitance.
   btw. I think the MOSFET should also be considered.
   john

6. A couple bits in general… High value resistors require careful handling, a mere finger print in the wrong place can throw a real wrench into the works. The same can be said about high impedance measuring circuits. The LMC6001 for example has a spec of 25pA, but unless extreme care is taken, its near impossible to achieve that level of performance. Cleanliness is key, and often times flying the lead wires of such devices is a more manageable solution than trying to maintain a pristine surface across ones circuit board.

7. http://www.techlib.com/science/geiger.html

8. you might want to look at contacting the author of this site http://www.techlib.com/science/ion.html for help in this project.

9. We have created a thread in the Libelium forum in order to publish the advances done in the design of the “radioactive sensor board” and to listen to the ideas and comments from contributors.

   Please consider to post here any idea which could help us with the design and election of the right Geiger sensor.

   http://www.libelium.com/forum/viewtopic.php?f=15&t=1791

10. SparkFun has a great write-up with schemaitcs and everything.
    http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=132

    You can also buy it here:
    http://www.sparkfun.com/products/9848

    It is actually a relatively inexpensive USB enabled unit.

11. that is the idea.
    we want to get a cheaper model. For this reason the design we are making in Libelium consists just in the sensor “part”. Then it will be pluged to the Arduino or Waspmote shields (which contain the microcontroller and the user interaction electronics).
    The idea of using the SBM-20 instead of the LND-712 Geiger tube is also to get a better price.
    Anyway, the idea is to make a model compatible with most of the Geiger tubes in the market today.

    David.

12. I really like the idea of helping out Japan, but if/when you have built this radiation detector I hope it will be available in the store! I’d really like to buy one thats cheaper than Sparkfun ;D

13. John, thanks for the prompt reply.

    What is the source of the noise that makes them noisy, is it predominantly thermal or caused by background radiation?

    I think you see where I am going with this…

    BTW It seems my idea is not new.. here is a similar sounding notion.
    http://www.freepatentsonline.com/4394676.html

14. Hi AndyH,

    In principle you are correct, But crystaline (and uC) solar cells are not made with electronic grade silicon, therefore they would have much more noise than pin photodiodes. Maybe a-Si could work, if they are thick enough, depending on the energy of the gamma radiation, I think that some 3µm is necessary.

    john

15. I have a question, would a photovoltaic cell detect radiation in a manner similar to a pin diode?

    They share a very similar structure. If so, would it not be possible to construct a simple light filter and cell sandwich to produce a very cheap radiation detector.

    Anybody know the answer?

16. Hello.
    Your thesis seems interesting. I have never heard the possibility of using a MOSFET as a radiation detector, it could be useful in other fields apart from GCs.
    Could please send me a copy of your work?
    Thanks

17. Hi Matthew,

    
    Matthew crenshaw:
    
    I have a sparkfun detector node setup at http://www.twitter.com/geiger93933 (marina, ca) that id like to add to any monitoring network.
    VA:F [1.9.6_1107]Rating: 0 (from 0 votes)

    How about Pachube? It seems that you have done connecting your geiger counter to Twitter, posting to Pachube might be easy task.

    http://community.pachube.com/node/608

18. I just built a geiger counter using a surplus geiger tube I bought off ebay for $15. For a power supply I used a sub-$3 disposable camera flash unit. It required a bit of hacking, but I have all the details here:
    http://madscientisthut.com/wordpress/?p=569
    and a video of it working here:
    http://www.youtube.com/watch?v=v4rDOSIOL84
    Right now it’s using an oscilloscope as the output because it’s what I have beside me, but I’ve built $2 audio output detectors for GM tubes before, and my blog details list a couple sites that have schematics for cheap audio detectors.

19. I dont know what the point of this would be, I could see doing it for fun. IF something happens you will know. Most people wouldnt know what to do with the reading of a geiger counter. This is not like fallout 3 where you run away when it starts clicking and shoot up some rad-x.

    Anyway, for a small power supply to drive a GM tube an inverter for a cold cathode lamp. There is info and schematics on buiding a geiger counter around one here:

    http://www.coultersmithing.com/forums/viewtopic.php?f=7&t=244

    That forum is a good site in general if you are interested in nuclear and other fun stuff.

    http://www.coultersmithing.com/forums/index.php

20. I have manufactured photodiode based alpha radiation detectors before that run on 9v.

    The key is choosing a photodiode that has a metal casing and glass window (which you will remove), because for alpha and beta particles you’ll want to expose the silicon to as many particles as possible.

    I have never gotten this to work correctly with non-milspec parts, but by coincidence I just received the parts I need to give it a shot. If it works I will let you know within a week. The PIN diode, three opamps, and an LM386 should produce something useable, and cost around 15$ in parts to build in small quantities.

    If you need circuit diagrams before then you may contact me by email.

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