• Tag Archives radiation

  • Detecting Radon with an ionization chamber

    Posted on by Johan

    Since I am interested in radiation I have been looking into ways of detecting radon and logging the results electronically. There are different ways of detecting radon.There are alpha track detectors which measure radon by having the alpha particles damage plastic and analysing the material later. Lucas cells are used to take an air sample and count the amount of alpha decays detected by a ZnS(Ag) scintillator and a photomultiplier.

    Alpha particles are strongly ionizing due to the fact that they are heavy particles that easily interact with matter. They have enough energy to hit a zinc sulphide scintillator and be visible to a dark-adapted human eye.

    A different way of detecting alpha particles is measuring the amount of ions they generate when they travel through a distance of air. By using an ion chamber, these ions can be converted into a measurable current, and even a discrete current pulse for each alpha ionization event.

    I found Alan Yates’ “Ion Chamber Alpha Particle Counter” to be easy to build. It is a small ion chamber with a JFET and a small circuit using a plain TL072 opamp.

    Some notes for anyone building this circuit:

    • A nice ion chamber can be made using a BNC male to SO-239 adapter and the screw hull from a PL-259 connector. Remove the teflon/plastic from the SO-239 end and solder the source of the JFET to the center pin and the drain to the wall. I covered one end of the screw hull with copper tape and punched a lot of holes in it to allow air to enter the ion chamber
    • Shielding of the JFET is critical, if shielding is insufficient the circuit will detect electric fields from static charges, mains voltage etc. and become unstable.
    • The circuit shows a 2N5484, I used a J201 that I intended to use for another type of alpha detector. I did not need to change the 560 ohm resistor on the source of the JFET.
    • It usually takes a minute for the circuit to settle down. This is because the gate of the JFET is floating and slowly charges up to a stable voltage. Before this happens no proper detections can take place.
    • This is a slow detector, when an alpha particle strikes it takes 100’s of milliseconds for the charge to leak away. During this time no other particles can be detected. In practice this is not a problem since alpha count rates even in high radon environments will not exceed the maximum count rate.

    This circuit is highly recommended for people wanting to research radon. It is easy and cheap to build, does not require high voltages and could be easily adapted to enable logging with microcontrollers. The last thing is a matter of converting the output into a 5/3.3V signal using a voltage divider and connecting it to a microprocessor GPIO pin. I am thinking of using a ESP8266 and ESP Easy’s pulse counting feature to make radon measurements available on the network/internet.

    Here is a video of my build of this circuit in action:

     


    📂This entry was posted in Electronica english wetenschap/science 📎and tagged

  • Interfacing the Uradmonitor with the Internet of Things, MQTT and Pimatic

    Posted on by Johan

    Intro

    For some time I have owned a Uradmonitor model A unit. This is a radiation monitoring solution which measures radiation and makes it available on a website. Connect it to your local network, and it will automatically get an IP address and start logging to www.uradmonitor.com. There you can find the stations and associated readings on a map.

    Since the Uradmonitor has a webinterface it is easy to scrape the data and send it elsewhere. For example, the CPM can be displayed on a VFD display or displayed in domotics applications.

    At home I try to make any sensor reading available using Mosquitto/MQTT. It is a lightweight, easy to use protocol to distribute dynamic data. Besides the Uradmonitor, multiple NodeMCU ESP8266 units running ESP Easy publish their sensor readings to the local MQTT server. All of this is done by Mosquitto running on my Debian ARM NAS and a Raspberry Pi running Raspbian and Pimatic.

    Scraping and publishing to MQTT

    First off I scrape the data from the Uradmonitor webpage using curl. Then, after some awk and html2text processing it is published to my local MQTT server using the mosquitto_pub MQTT publishing client.

    #!/bin/bash
uradmonitorcpm=$(curl -s http://<ip of uradmonitor/ | html2text | grep radiation | egrep -o '[0-9.]*')
mosquitto_pub -m $uradmonitorcpm -t /uradmonitor/cpm

    This bash script runs every minute using /etc/crontab and updates the local MQTT server with the latest measurement. The command ends with the MQTT topic which is the “address” of the dynamic value on the MQTT server.  Please note that mosquitto_sub does not need an IP address when publishing to localhost/127.0.0.1 since that is a default of the client. To specify a host, use the -h <ip address of mqtt server> option. Continue reading → Post ID 3618


    📂This entry was posted in computers-networking Electronica english 📎and tagged