Artist Inadvertently Builds Hodoscope

A Hodoscope is an instrument used to determine the trajectory of charged particles. It’s built out of a three-dimensional matrix of particle detectors – either PIN diodes or Geiger tubes – arranged in such a way that particles can be traced along coincident detectors, revealing their trajectory.

This is not a hodoscope. It’s a chandelier. This chandelier is made of 92 individual Geiger tubes, each connected to a single LED fixture and a speaker. When a charged particle flies through the room and hits a Geiger tube, the light fixture lights up, a ‘click’ plays on the speaker, and the entire room is enveloped in light for a short moment in time. If, however, that charged particle continues on to another Geiger tube, the trajectory of the particle can be deduced.

The purpose of the installation – beside just being art or something – is to show the viewer sources of radiation and normal levels of radioactivity due to terrestrial and cosmic sources. Of course the spacing of these detectors is rather large – it’s made to fit in a gallery – and there is no connection between the detectors, making a coincident circuit impossible. If you want a real hodoscope, here you go.

This installation can be seen at the Burchfield Penney Art Center in Buffalo, NY through April 12. If you’re in the area, go there and eat a banana. Video below. Thanks [David] for the tip.

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Turning a phone into a Geiger counter


We’re no stranger to radiation detector builds, but [Dmytry]’s MicroGeiger prototype is one of the smallest and most useful we’ve seen.

The idea behind the MicroGeiger comes from the observation that just about every modern smartphone can provide a small bit of power through the microphone jack. Usually this is used for a microphone, but with the right circuit it can be stepped up enough to power a Geiger tube.

[Dmytry]’s circuit uses a hand-wound transformer but keeps the part count low; there’s only a few dozen caps, resistors, and diodes in this build, making the circuit much smaller than the Geiger tube itself.

Since [Dmytry] is powering a Geiger tube with a phone, it only makes sense that he should also record clicks from the tube with an Android app. Right now, the entire project is still in the prototype stage, but everything works and his app can detect radiation from one of [Dmytry]’s sources.

The code and schematics for the MicroGeiger are available on GitHub, with a video of the project in action below.

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A very tiny gamma ray detector


When you think of a radiation detector, you’re probably thinking of a Geiger tube and its high voltage circuitry. That isn’t the only way to measure gamma radiation, though, and [Alan] has a great circuit to measure even relatively weak radiation sources. It uses a very small photodiode, and draws so little power it’s perfect for projects with the smallest power budgets.

The detector circuit uses a miniature solar cell and a JFET wired up in a small brass tube to block most of the light and to offer some EM shielding. This, in turn, is attached to a small amplifier circuit with a LED, Piezo clicker, and in [Alan]’s case a small counter module. The photodiode is actually sensitive enough to detect the small amounts of gamma radiation produced from a smoke alarm americium source, and also registers [Alan]’s other more powerful radioactive sources.

The circuit only draws about 1mA, but [Alan] says he can probably get that down to a few micoAmps. A perfect radiation sensor for lightweight and low power applications, and gives us the inspiration to put a high altitude balloon project together.

Solar Powered Wifi Radiation Sensor

Solar Radiation Detector

[Manish] packed lots of functionality into this radiation sensor module. The device is completely solar powered and weatherproof, so it can be mounted anywhere. It uses a Geiger Muller tube to monitor radiation and connects to the internet using wifi network to report the readings.

The design uses an Arduino Pro Mini to perform the monitoring and reporting. Wifi connectivity is provided by a RN-XV wifi module. A solar panel, Adafruit’s solar charger, and a LiPo battery are used to provide power to the device. It’s enclosed in Adafruit’s IP-66 rated weatherproof enclosure.

A custom Geiger Muller tube interface is used to interface with the tube. The interface is simple and cheap. It provides the high voltage required to drive the tube, and circuitry needed to detect the ionization events.

Once the device is connected to the internet, it uploads data directly to Cosm. This service lets the data be shared using Twitter, or accessed using an API. The project shows how to build a wireless networked sensor that directly connects to the internet for about $100.

Online radiation monitoring station


This is a Geiger counter which charts its readings on a webpage. [Radu Motisan] put a lot of time into the build and it shows. This thing is packed with features and the hardware choices were the best combinations found through several iterations of development.

In addition to radiation levels the sensor unit takes several other measurements. These include temperature, humidity, luminosity, and barometric pressure. All of the sensor data is monitored and gathered by an ATmega168 which can be charted on a webpage with the help of an ENC28J60 Ethernet chip. The collection and display of this data is detailed at the post linked above.

For those interested in the hardware development, [Radu] published many updates along the way. These are available in his forums posts, as well as his build log. He doesn’t have any videos of his recent work, but way back in May he did publish a clip (found after the break) which shows the testing of different Geiger tubes.

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Geigers on a plane

[Thomas] took a Geiger counter he built on a plane. Why? Because he can, much to the chagrin of airport security.

[Thomas]’ Geiger counter is built around an old Russian SBT-10A detector containing ten separate Geiger tubes. This tube was connected to a circuit containing a LiPo battery, a few high-voltage components, and an audio jack connected to the tubes themselves. When alpha, beta, or gamma radiation hits one of the Geiger tubes, an enormous click is sent to the audio jack and into the microphone jack of a small netbook.

Right after boarding a plane in Dublin, [Thomas] booted up his computer, started recording in Audacity, plugged in his Geiger counter, and stored his experiment safely in the overhead compartment. After landing in Prague a few hours later, [Thomas] saved the 247 MB .WAV file and began working on a way to convert clicks in an audio track into usable data.

The audio output on the Geiger counter overloaded the mic input on his netbook, making ‘event detection’ very easy with a small C app. After plotting all the data (seen above), [Thomas] had a complete record of the radiation on his 2-hour flight.

Because there was far less atmosphere to absorb cosmic radiation, [Thomas]’ radiation dose was 9.1 microsieverts. Much more than at sea level, but nothing even air crews need to worry about.

Detecting cosmic rays with 18 Geiger tubes

What do you do if you have 18 Geiger tubes lying around? [Robert] had an interesting idea to build a cosmic ray detector and hodoscope to observe the path cosmic rays take while flying through his lab.

[Robert]’s cosmic ray detector works by detecting the output 9 Geiger tubes on the y-axis and 9 Geiger tubes on the x-axis with a coincidence circuit. When a cosmic ray flies through the detector, it should trigger two tubes simultaneously. By graphing which of the two tubes were triggered on an array of 81 LEDs, [Robert] not only knows when a cosmic ray is detected, but where the cosmic ray was.

The detectors do pick up a little background radiation, but thanks to [Robert]’s coincidence circuit, he can be fairly certain that what he’s recording are actually high-energy cosmic rays.

Before building the 9×9 hodoscope, [Robert] built a similar drift hodoscope that simply plots the path a cosmic ray takes through an array of Geiger tubes. You can check out videos of both these cosmic ray detectors after the break.

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