11/05/2017 at 10:35 •
We setup the Cosmic Array in quite a large space at the rear of Maker Faire Adelaide at 8am.
Left to right - The Cosmic Array, then some units opened up so people can look inside, then my early Drift Hodoscope, then my 81 Pixel Hodoscope which was connected to a computer to play music and regenerative graphic.
Although it doesn't look it. It was quite busy as we where located right at the end of the Maker Faire.
Above is Paul Schulz, who has developed code for the Cosmic Array and was a great help all day. He will be doing a presentation at the next - linux.conf.au 2018.
A very busy day lots of questions and was the Winner for best backyard science.
10/30/2017 at 07:00 •
I am currently busy preparing for Maker Faire Adelaide this weekend and so I will have the 16 detectors running live, along with other detectors I have made and more details on its operation.
Maker Faire Adelaide is the largest Maker Faire in Australia and in the Southern hemisphere. Also the only Maker Faire solely run by volunteers. So if you are in Adelaide this weekend come and say hi!
10/06/2017 at 04:02 •
I'm currently exploring a new solid-state detector design using Pin Si Photodiodes, this is still a few months away. But will be a feature of a new cosmic ray detector designs to come. The main issue with using Geiger–Müller tubes and Photomultiplier scintillators as detectors is mostly cost. But also includes limited life and high voltages between 400 to 1600V DC which must also be low noise and regulated.
Solid state devices particularly Si Pin Photodiodes are capable of measuring both ionising radiation (Muons) and some added benefits like energy resolution, low voltage, low power, greater longevity and lower cost. But do have issues and compromises such as: more complexity, noise, and a small aperture size.
There are some specialist Photodiodes designed specifically for this application, but these are very expensive and difficult to source in small quantities for example:
- Manufacture First Sensor Part # 5014450 - has visible light filter
- Manufacture First Sensor Part # PS100B-7-CERPINE - has visible light filter
- Hamamatsu Part # S3590 - no visible light filter
Here is an example using the First Sensor 5014450 and an old CD V-700 Geiger Counter check source which is radium 226Ra. Although successful, the detector is expensive (~$50au) and still only has a relatively small aperture compared with a Geiger–Müller tube, so multiple detectors would be required.
There are lower cost of-the-shelf Pin Photodiodes such as the BPW34F which have been featured in many DIY radiation detector projects over the years. However, these have an even smaller aperture. So many will need to be connected together to increase it. However, they can not be simply wired in parallel due their combined capacitance. Here is rough layout that I have began experimenting with using JFETs to buffer each photodiode before amplification.
09/06/2017 at 09:26 •
The Splash Adelaide installation was very successful will allot of public interest and questions. The IoT setup also went well and we were able to live stream data to another computer where it was mapped into music using MAX/MSP software. The sounds in the following video include bell sounds from each detector and also the combined musical soundscape generated in MAX/MSP.
- 09/02/2017 at 08:01 • 0 comments
09/01/2017 at 13:25 •
The last 2 months I have been preparing for my first demonstration project with an installation of an array of 16 detectors in Adelaide Elder Park, South Australia as part of the Winter Splash Adelaide. It was a lot more work than I expected, but I'm pleased to report it has been successful. It will be installed on the 2/9/2017. More to report soon. Here is a video of the build process from prototype to completed units tested in my back yard. The sound of the detectors will be recorded at the event soon.
07/30/2017 at 05:41 •
The software for the detectors has been installed on the SD Cards, and prepared for posting to Robert for installation in the Raspberry Pi Zero's.
This installation contains new audio files.
The OS Image being used is Raspbian Jessie (2017-07-05-raspbian-jessie-lite).
A Raspberry Pi 3 is used as it provides a wired network interface, as well as a screen and keyboard.
Once the OS Image has been written to the SD Card (16GB), it is booted with screen and keyboard attached and via the configuration tool (raspi-config), the hostname is set (cosmic-array-*-*), the SSH service is enabled and the Pi is rebooted.
SSH keys are manually copied to the card using ssh-copy-id.
An ansible playbook is used to connect to the system via SSH and setup the wireless, additional packages and to checkout the cosmic-array software from GitHub. While this might be slightly overkill for individual cards, these configuration tools will allow all 16 detectors to be modified and updated easily later on.
Finally, the 'config/install.sh' script is run from the cosmic-array software to setup boot parameters (audio system overlay), programs started on boot and audio volume settings. This script will probably be included in the ansible setup process in the future.
07/28/2017 at 11:04 •
The code, data and files required to drive the RaspberryPi Zero has now been made available via GitHub.
This code is 'feature complete' for the standalone cosmic array sensor.
Suggestion, Comments, Branching and Patches welcome. Distributed under GPL v3.
07/23/2017 at 11:35 •
Recently we completed work on Cosmic Array sound and IoT using the new Raspberry Pi Zero W. But the addition of a Raspberry Pi and the audio amplifier caused the detector to trigger more often than it should. At first, it didn't seem to be an extra load on the 5V regulator. Nor the Geiger-Muller tubes after a check with a radioactive check source and DSO.
Then I remembered! I cut back on components to simplified the circuit design and cut costs. One of the components I removed was a 4V7 Zener diode on the output of the 10pf coupling capacitor connecting the Geiger-Muller tube to the 555 monostable oscillator trigger pin 2. At the time of the redesign, I forgot the real reason for the Zener just assuming it was there for voltage protection between the high voltage and low voltage sections.
The 555 timer acts as both a Schmitt trigger to shape the negative pulse from Geiger-Muller tube to a +5VTTL and increases the pulse width. Pin 2 of the 555 is the trigger for the monostable oscillator when it detects ground travelling pulse. So Pin2 is held at the supply rail voltage by a 47k resistor so when the high impedance negative pulse from the Geiger-Muller tube it triggers.
The trouble came when both the Raspberry Pi and the audio amplifier where added to the 5V supply rail that supplies the 555 circuits. Although the quiescent state supply rail measured 5V after coincidence is detected, the Pi plays a wave file and then the Audio amplifier causes ripple currents the trigger the other 555 monostable oscillators causing them to trigger randomly resulting in more ripple currents.
The solution is to hold pin 2 at 4.7V with a Zener diode and the problem goes away. The new boards are also designed with a higher current regulator further reducing this effect.
07/21/2017 at 08:45 •
To give each element of the Cosmic Array sound and IoT we are using the new Raspberry Pi Zero W.
The Raspberry Pi Zero W doesn't have sound but with the addition of a low pass filter thanks to information on Adafruit Learn Blog this was quite straight forward.
Amplified by a 5V 3W Class D amplifier based in the PAM8403 which is cheaper to source as a fully assembled PCB than a chip on its own.
I needed 16 4 x 4 Raspberry Pi Zero W for an Art installation at Splash Adelaide and although there has been a one order per customer limit imposed by the Raspberry Pi Foundation on suppliers.
Thanks to wonderful local Hackerspace Adelaide community we have been able to source 16 x Raspberry Pi Zero W for the task.