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  • Trinket powered geiger counter

    Lately I have been messing around a bit with microprocessor powered geiger counters. One smart guy came up with the idea of generating high voltage using PWM signals from the microprocessor itself. With some additional external parts a HV supply and negative going pulse suitable for microprocessors is easy to make. Here is a schematic I came up with:

    gm counter interface

    The circuit works as follows: A ~1 Khz squarewave turns the MPSA44 high voltage transistor on and off, generating high voltage when the  inductors current is shut off. The voltage depends on the pulse width of the square wave which can be tweaked in software. The 1N4007 diode rectifies this voltage, and the HV cap removes most of the ripple on this voltage. The resistor limits current to the GM tube. The current pulses from the tube generate a voltage drop over the 100K resistor which turns on the BC546. When this happens the voltage through the 10K resistor is pulled to ground, generating a negative going pulse each time the GM tube detects an ionizing ray or particle.

    To drive this circuit I used my new Adafruit Trinket, a small board with a Attiny85 microprocessor. Using the tutorials on the Adafruit website it is easy to work with from the Arduino environment. Here is the code:

    void setup() {
     analogWrite(0, 30); //starts PWM on pin 0, generates about 400V
     analogWrite(1, 255); // needed to get LED to full brightness
     attachInterrupt(0,countPulse,FALLING); // attach interrupt to pin 2
     }
    void loop() {
     //nothing much really
     }
    void countPulse(){
     //pulse led
     digitalWrite(1, HIGH);
     delay(100);
     digitalWrite(1,LOW);
     }

    And here is a video of the setup in use:

     

    Of course it is rather wasteful to only use the microprocessor to generate PWM and flash a LED. I plan on implementing counting and serial output in software later. Unfortunately the Trinket does not have native serial USB capability but bit banging a serial signal on one of the pins should work fine according to several sites. Then it is just a matter of adding a cheap PL2303 serial to USB adapter.

    Update 18/4/2014

    Added serial logging capability. Using a tx only software serial library, the Trinket outputs the measurements in CPM each 10 seconds on pin 4. New code:

    // Trinket GM counter by Johan/dynode.nl
    
    //counting vars
    long count = 0;
    long countPerMinute = 0;
    
    // init softserial only tx on pin 4
    #include <SendOnlySoftwareSerial.h>
    SendOnlySoftwareSerial mySerial (4);
    
    void setup() {
      mySerial.begin(9600); // init serial 9k6
      analogWrite(0, 30); //starts PWM on pin 0, generates about 400V
      analogWrite(1, 255); // needed to get LED to full brightness
      attachInterrupt(0,countPulse,FALLING); // attach interrupt to pin 2
      mySerial.println ("Trinket GM counter starting..."); 
    }
    
    void loop() {
      delay(10000); //the count is incrementing during this delay
      countPerMinute = 6 *count;
      mySerial.println (countPerMinute);
      count=0; //reset the count
    }
    
    void countPulse(){
        count++;
        //pulse led when count is increased
        digitalWrite(1, HIGH);
        delay(100);
        digitalWrite(1,LOW);
      }

    Example serial output using cheap eBay USB<>TTL serial adapter:

    Trinket GM counter starting...
    84
    12
    6
    0
    402        <--- thorium bearing mantle held next to GM tube
    996
    1218
    1146
    1074
    1104
    
    

    There still need to be some tweaking done, the circuit is quite susceptible to electromagnetic interference which causes erroneous counts.


  • Streaming radio receivers with the Raspberry Pi

    rpi_audio_stream

    The Raspberry Pi is a small computer that has become very popular. Lots of applications and hardware hacks have been made for it. You can run various software like web/file/printservers, read out sensors, the possibilities are endless.

    I own multiple Raspberry Pi’s, one is a test platform for sensors, and a new one pictured above will be dedicated to audio streaming. I use the software packages darkice and icecast2 to capture the audio from an USB audio card and make it available on the internet.

    To stream audio with the RPi you’ll need the following hardware and software: Continue reading  Post ID 1326


  • PMTs and scintillation probes

    quickprobe

    temporary probe with NaI(Tl) crystal, PMT, socket with voltage divider and BNC socket

    Following is a little guide to using photomultiplier tubes in DIY scintillation probes.

    Photomultipliers are vacuum tubes that convert light into electrons and multiply the resulting current up to millions of times. They are used to detect the minute flashes of light generated by scintillators, materials that convert gamma and x-rays into visible light.

    How to use these tubes? There are some things you need to remember when working with PMTs.

    Continue reading  Post ID 1233


  • Eye/oog update

    Posted on by Johan

    English follows below…

    Straks gaat er een ondertekende brief de deur uit en geef ik akkoord voor een behandeling aan mijn linkeroog en medewerking aan een wetenschappelijk onderzoek.

    Mijn linkeroog gebruik ik al tijden niet meer door lensintolerantie en ik zou graag weer eens met beide ogen willen zien.

    Volgens de oogarts is het voor mijn linkeroog mogelijk om een gedeeltelijke hoornvliestransplantatie (DALK) uit te voeren waarbij het achterste laagje, het endotheel, behouden zal blijven. Dit heeft een aantal bijzondere voordelen, de wond zal beter helen, de kans op afstoting is lager en het resultaat is duurzamer dan de transplantatie van de gehele dikte zoals in mijn rechteroog.

    Het wetenschappelijke onderzoek  gaat bekijken of een bepaalde methode om laagjes hoornvlies te scheiden voordelen biedt ten opzichte van de traditionele methodes. Dit is belangrijk, want bij DALK operaties komt het bij een vijfde van de operaties voor dat men de laagjes niet goed kan scheiden en dat men toch een ouderwetse transplantatie van de gehele dikte van het hoornvlies moet uitvoeren.

    Nu is het dus wachten op de operatie, een groffe indicatie van de arts is een half jaar. Uiteraard zal ik na de operatie weer de gebruikelijke updates geven.

    Continue reading  Post ID 1194


  • YouTube beginning to suck

     

    I spend a lot of time watching video’s on YouTube. Lots of interesting channels about hardware hacking, radiation detection, electronics and stuff.

    But lately something has changed. YouTube continually tries to push unrelated or unwanted videos on me. On the right side I used to see only videos that were more or less closely related to the video. But nowadays completely unrelated videos pop up. The recommendations seem to be based on two things:

    – Whatever videos you watched in the past. But even with all the history deleted, videos that I watched continue to pop up on the right side, even when they are completely unrelated to the video being watched.

    – Random stuff that is supposed to be “fun” but are rehashes of other videos, memes and stuff. It seems that YouTube sells these spots for $$$ to enable people to promote push their videos onto the YouTube audience.

    Continue reading  Post ID 1128


  • Thrash metal appreciation post

    I grew up listening a lot of metal. When you are young you will get easily impressed by all kinds of music. I used to listen to highly accessible and melodic stuff, such as power metal, gothic metal, black metal with lots of keyboards. I don’t listen to much of that stuff anymore. As I got older I began listening to less technical and melodic music. One of the genres I knew but didn’t interest me in particular was thrash metal. Sure, as virtually every young metal listener I discovered bands like Metallica, Megadeth, Sepultura, Slayer etc…

    My interest in (hardcore) punk music of more recent years brought me back to listening thrash. Similar to punk it is loud, fast, contains anti-establishment lyrics and usually doesn’t dwell too much on the technical stuff.

    Some years ago thrash metal got a revival and showed that there are still a lot of good bands around. Also, some bands decided to use a more humorous approach in the lyrics. Since I like extreme music but often find the lyrics crap (the usual stuff about death, destruction, the apocalypse etc. over and over again) I think this is a good thing because in the end, a lot of people go to gigs to drink some beers and have fun!

    So, here some fine examples of thrash :)

    Kreator, one of the big German thrash bands, still raging on after decades:

    Municipal Waste is one of the revival bands and is highly influenced by crossover thrash. Also they make funny lyrics and videos which is GOOD!

    Continue reading  Post ID 1118


  • Eye/oog update post

    Visual field test

    English summary below…

    De laatste tijd gaat het goed met mijn ogen. Ik draag vrijwel de hele dag een lens en kan dus over het algemeen mijn werk goed doen. Oogdruk was bij de laatste meting 12 dus gaat langzaam omlaag zoals verwacht. De baerveldt implant is steeds minder zichtbaar in het oog omdat alles minder rood is geworden.
    Het laatste gezichtsveldonderzoek (zie boven) liet geen achteruitgang zien. Continue reading  Post ID 1102


  • Some rad links…

    Below are some interesting links about radiation (detection) that I have collected over time:

    Have questions about geiger counters, the CDV-700 or gammaspectrometry? Just go to these Yahoo groups:

    CDV700CLUB : The CDV 700 Club is a forum for like minded individuals that enjoy collecting, fixing up, and using geiger counters and other r

    GeigerCounterEnthusiasts : PAGE 2…for Archives go to PAGE1

    GammaSpectrometry : Gamma Spectrometry

    Want videos? Check out these awesome Youtube channels:

    http://www.youtube.com/user/antiprotons?feature=watch

    http://www.youtube.com/user/antiprotons?feature=watch

    Want pictures? Check out the Flickr Radioactivity pool: Continue reading  Post ID 1080


  • New geiger counter build

    I’m currently building a GM counter for a friend and was looking for nice, low
    power circuits working on 9V cells.

    I found this circuit which is derivative of Charles Wenzel’s designs:

    http://www.mikrocontroller.net/attachment/103170/Geiger_Hochspannung.png

    Components are fairly basic apart from the HV transistor and zeners. The other
    transistors can be basically any small signal PNP/NPN transistor from the
    junkbox. I used BC547 and BC557 and a MPSA44 HV transistor. Continue reading  Post ID 1068


  • Baerveldt implant update

    English summary below as usual

    Het is nu ongeveer 2 ½ maand geleden dat mijn rechteroog van een Baerveldt implantaat is voorzien om de te hoog opgelopen oogdruk onder controle te krijgen. Door lang gebruik van corticosteroïden is er secundaire glaucoom opgetreden welke een klein defect in mijn zichtveld rechts heeft veroorzaakt.

    Bij een Baerveldt implantaat zal de oogdruk na de operatie behoorlijk variëren, en dat heb ik ook gemerkt. Na de operatie was deze redelijk hoog, tot 28 mmHg en zakte deze weg naar rond de 20 en bij het opengaan van het buisje naar rond de 10. Vooral dit laatste was duidelijk merkbaar, door de plotselinge drukverandering had ik opeens een soort donkere vlek onderin mijn zichtsveld zitten. Volgens het ziekenhuis waar ik snel voor controle langs ging was er verder niks aan de hand met het oog. Continue reading  Post ID 1064