Radiation detector, help needed!

We got inquires from Shigeru in Tokyo about Geiger Mueller Tube, as the nuclear accident in FUKUSHIMA is escalating.

Can open hardware community do something to help in this? Seeed Studio is now sourcing sensors, then assemble quick measurement tools,  ship as many/fast as possible to Japan.

Since we have no previous experience with such device,  your help is needed!

If you have experience in making such device, some quick questions:

1. What would be the right sensor for such detection? Will the education purpose GM tube work?

2. Any recommended peripheral circuits?

3. Does such Geiger counter needs special calibration? Or can we calibrate it with commercial device?

All creations will be open source and donated, thank you for helping out!

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109 thoughts on “Radiation detector, help needed!

  1. *Radiation Sensor Board for Arduino RELEASED*

    Quick Overview:
    Detect Alpha, Beta and Gamma radiation integrating any Geiger Tube which works in the range 400V – 1000V and read this levels using Arduino. As well as from the terminal, the radiation levels can be shown using different actuators:

    – Piezo: it allows us to hear the typical “chirp” common in the radioactivity counters
    – Leds: 3 green and 2 red let easily to show low, medium and high levels
    – LCD: it displays the counts per minute (cpm) and the equivalent absorbed energy levels in Servants (µSV/h).

    Read the Tutorial:
    http://www.cooking-hacks.com/index.php/documentation/tutorials/geiger-counter-arduino-radiation-sensor-board

  2. Just a note, I’m using an arduino to generate very short pulses into a 120:1 ratio transformer.

    Using fast recovery diodes in a full wave rectifier generates several thousand volts with almost no wasted power (on a 5-volt supply).

    So much voltage that I only have to pulse the thing 25 times/sec to generate 900 volts for my system.

  3. Diodes take time to reverse polarity. During this time they act like resistors and eat power.

    Normal diodes take a relatively long time to reverse, and the excess power they dissipate can be enough to burn out the diode over time.

    You can get fast recovery diodes with a much smaller reversal time. This results in less dissipated energy which is easier on the diodes, and less energy is wasted by the circuit.

    In my system, replacing the 25KV diode with an ultrafast increases the output by 20 volts.

    Ultrafast recovery diodes are only a little more expensive than regular diodes:

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320579572234&ssPageName=STRK:MEWNX:IT

  4. (I’m about 2 days behind you in development of my HV board 🙂

    I wrote an arduino program that lets me type in a pulse width and repetition rate, then generates pulses on one of the outputs.

    This goes into a power MOSFET looking into a flash transformer. No (other) transistors, no oscillators, nothing but the micro and the MOSFET.

    This has allowed me to experiment with pulse widths and repeat rates. Using this method I’ve been able to find the “sweet spot” for my transformer: if the pulse is any narrower it generates less output voltage, and if it is any wider it doesn’t generate more voltage.

    Very little current is therefore wasted, so the system will have the a long battery time.

    Eventually I plan to use the micro to adjust the output voltage by comparing against a voltage reference.

    Contact me on my website if you’re interested in the pulse generator source code.

  5. I have a new design for a cheap GM tube and am looking into seed funding to get manufacturing started. The design is amenable for very high volume manufacture and will be a basic grade device. Any insight on liner materials for both organic and halogen quench gases is greatly appreciated.

  6. I’ve just finished reviewing all entries in this blog from the beginning, including most of the circuit links.

    Any reasonable circuit can be used to generate the HV needed to run a GM tube. These are usually a pulse oscillator
    looking into a transformer, then a couple of CW multiplier stages as needed.

    Be aware that GM tubes are insensitive to SMALL variations in voltage SO LONG AS the voltage is within the operating
    range of the tube.

    Most of the circuits linked have no regulation of the output voltage, which means that the voltage will be wildly
    variable depending on the method of generation, frequency, and battery voltage.

    With no regulation you will not be able to claim that measurements are comparable, even for units using the same
    circuit. The voltage variation has to be at least less than 5% for comparisons – preferably less.

    Finally, running a tube with too much voltage can cause cascade breakdown, which will give you an anomalous really
    high reading *and* will eventually kill your tube.

    (I’m assuming you don’t want anomalous very high readings.)

    For scientific validity (and yes, what you are doing is scientifically valid – ignore the nay-sayers) you will need a
    stable, regulated HV output for all your units.

    This is straightforward – a series of high-voltage zeners in series (plus a couple of low voltage to add to the
    correct value). High voltage zeners are cheap and available:

    http://cgi.ebay.com/50-PC-1N4764A-ZENER-DIODES-100-VOLTS-1-WATT-/280648014439?pt=LH_DefaultDomain_0&hash=item4157ecda67

    Look on the lower right corner of this schematic to see what I’m talking about:

    http://home.comcast.net/~dprutchi/cdv700pro.pdf

    You will want to construct a zener chain to generate the correct voltage for your own tubes.

    A second way to regulate the output is to measure it, compare against a known source (such as a 2.5 volt zener), and
    use the difference to adjust the output. The Maxim app note uses this method:

    http://pdfserv.maxim-ic.com/en/an/AN3757.pdf

    High impedance is key – you need a very large resistance so as not to load down the output.

    Regulating the GM voltage is something that you really should do if you want valid results.

  7. I’ve just finished reviewing all entries in this blog from the beginning, including most of the circuit links.

    Any reasonable circuit can be used to generate the HV needed to run a GM tube. These are usually a pulse oscillator looking into a transformer, then a couple of CW multiplier stages as needed.

    Be aware that GM tubes are insensitive to SMALL variations in voltage SO LONG AS the voltage is within the operating range of the tube.

    Most of the circuits linked have no regulation of the output voltage, which means that the voltage will be wildly variable depending on the method of generation, frequency, and battery voltage.

    With no regulation you will not be able to claim that measurements are comparable, even for units using the same circuit. The voltage variation has to be at least less than 5% for comparisons – preferably less.

    Finally, running a tube with too much voltage can cause cascade breakdown, which will give you an anomalous really high reading *and* will eventually kill your tube.

    (I’m assuming you don’t want anomalous very high readings.)

    For scientific validity (and yes, what you are doing is scientifically valid – ignore the nay-sayers) you will need a stable, regulated HV output for all your units.

    This is straightforward – a series of high-voltage zeners in series (plus a couple of low voltage to add to the correct value). High voltage zeners are cheap and available:

    http://cgi.ebay.com/50-PC-1N4764A-ZENER-DIODES-100-VOLTS-1-WATT-/280648014439?pt=LH_DefaultDomain_0&hash=item4157ecda67

    Look on the lower right corner of this schematic to see what I’m talking about:

    http://home.comcast.net/~dprutchi/cdv700pro.pdf

    You will want to construct a zener chain to generate the correct voltage for your own tubes.

    A second way to regulate the output is to measure it, compare against a known source (such as a 2.5 volt zener), and use the difference to adjust the output. The Maxim app note uses this method:

    http://pdfserv.maxim-ic.com/en/an/AN3757.pdf

    High impedance is key – you need a very large resistance so as not to load down the output.

    Regulating the GM voltage is something that you really should do if you want valid results.

  8. (Your system ate my 1st and 2nd post?)

    GM supplies put out high voltage, but very little current. So little, that a standard 10 megohm meter will load down
    the output and give erroneous readings.

    To avoid this you will need a high-impedance probe. Here’s my tutorial on how to do that, along with the theory:

    http://www.okianwarrior.com/Builds/Hardware/HIProbe/

    I’ve been playing around with the circuit from this page. It’s easy to build and easy to modify:

    http://pdfserv.maxim-ic.com/en/an/AN3757.pdf

    The voltage at the drain of the transistor is about 70 volts, so only a couple of CW [Cockcroft Walton multiplier]
    stages is needed to bring that up to the voltage you will need.

    My tubes are bigger and need a larger voltage and I didn’t want a really long CW chain, so I substituted an audio
    transformer for the inductor.

    The transformer is commonly available at Radio Shack (273-1380), and has 70 ohms on one side and 0.63 ohms on the other.

    Then change the timing cap to 0.1 uF to bring the oscillator down to 1 Khz. (The transformer won’t work at megahertz
    frequencies.)

    The transformer gives 250 volts of output, so a single CW stage should give you enough voltage to run your tubes.

    Then a diode for rectification, and a 1 megohm resistor for current limiting.

    You can use a series of 120 volt zeners for voltage regulation and dispense with the comparator and feedback
    regulation. The comparator only turns the oscillator on and off as needed – just tie the 100K resistor to V+ and let
    the oscillator run all the time.

  9. (Repost – your system ate the first one)

    GM supplies put out high voltage, but very little current. So little that a standard 10 megohm meter will load down the output and give erroneous readings.

    To avoid this you will need a high-impedance probe. Here’s my tutorial on how to do that, along with the theory:

    http://www.okianwarrior.com/Builds/Hardware/HIProbe/

    I’ve been playing around with the circuit from this page. It’s easy to build and easy to modify:

    http://pdfserv.maxim-ic.com/en/an/AN3757.pdf

    The voltage at the drain of the transistor is about 70 volts, so only a couple of CW [Cockcroft Walton multiplier] stages are needed to bring that up to the voltage you will need.

    My tubes are bigger and need a larger voltage and I didn’t want a really long CW chain, so I substituted an audio transformer for the inductor.

    The transformer is commonly available at Radio Shack (273-1380), and has 70 ohms on one side and 0.63 ohms on the other.

    Then change the timing cap to 0.1 uF to bring the oscillator down to 1 Khz. (The transformer won’t work at megahertz frequencies.)

    The transformer gives 250 volts of output, so a single CW stage should give you enough voltage to run your tubes.

    Put the output through a diode and cap for rectification, then a 1 megohm resistor for current limiting.

    You can use a set of 120 volt zeners (in series) for voltage regulation and dispense with the comparator and feedback resistors. The comparator only turns the oscillator on and off as needed – just tie the 100K resistor to V+ and let the oscillator run all the time.

  10. GM HV sources generate almost no current. So little, that a standard 10 megohm digital meter will load down the output and give you erroneous readings.

    For proper measurement, you need to build a special high-impedance probe to use with your VOM.

    Here’s my tutorial on how to do this, with the theory:

    http://www.okianwarrior.com/Builds/Hardware/HIProbe/

    I’ve been using the HV circuit from the following APP note:

    http://pdfserv.maxim-ic.com/en/an/AN3757.pdf

    The output from the coil going into the Cockcroft Walton multiplier [ie – the voltage at the drain on the transistor] is about 70 volts, which means only a couple of multiplier stages will be needed to run the smaller GM tubes.

    My tubes are bigger, and I don’t want a long CW chain so I have replaced the coil with the primary of an audio transformer.

    I also changed the timing cap to be 0.1 uF, which puts the frequency at about 1 Khz. (The audio transformer doesn’t handle high frequency.) The transformer output is ~250 volts.

    That would be about right for your tubes – double it with a CW stage and then put it through a diode (for rectification), a 1 megohm resistor (for current limiting) and a series of 120 volt zeners to ground for voltage regulation.

    The audio transformer is available from Radio Shack (273-1380) and has 70 ohms on one side and 0.63 ohms on the other.

    The comparator just monitors one stage of the CW chain and turns the oscillator on or off as needed to keep up the voltage.

    If you use a zener chain for regulation, you won’t need the comparator or the resistor chain that it measures. Just connect the 100K resistor to V+ to keep the oscillator running all the time.

    I’ve built and used this circuit. It works, and it’s blood simple.

  11. @rich 2#28 Thanks for your link to the Kearny Fallout Meter, which was introduced in comment 1#24 above. Since today, an actual how-to is online http://www.youtube.com/user/kmomutube
    The strength of this unit is it´s calibration by design with materials available in many homes.
    It may provide a rough advise about the actual radiation weather before leaving home.
    The Cons are: It is not designed for continuous monitoring and needs special care under high humidity conditions (rain may washout radiation particles from heigths down, but the KFM may fake unreal high radiation level if getting wet inside).
    We discussed the idea to include it in a THS Kimono lantern, but it doesn´t work without metal can housing. Anyway, there are some challenges how to improve the 1979 design by solar-powered Arduino ;-).

  12. Right now, I’m looking into CCFL flyback transformers. Coilcraft has the FL2810-1L which has a 1:100 turns ratio. I picked up some surplus CCFL inverters locally in Akihabara and will test those out. I also got in 10 of the SBM-20 geiger tubes and will test. I’m going to be asking for a quote from LND on beta/gamma geiger tubes which I think will be less than the LND-712.

    Tokyo Hackerspace will also be assisting RDTN.org and some of the volunteers from the group will be attending hackerspace meetings. They have radiological guys with expertise in the field so it should be interesting.

    I haven’t had too much time to work on the geiger schematic recently since we’re busy on more immediate needs for tsunami survivors. But I should be able to get back on it soon. I’ll keep everyone posted.

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