There were lots of questions by email, on groups or on different channels regarding uRADMonitor. Many people are familiar with Geiger Counters, radiation and the basics on nuclear physics, but for some, the uRADMonitor remains a tiny black box – intriguing, but totally unknown.
To answer some of these questions, here are a few more details.

The uRADMonitor is a completely assembled and functional radiation dosimeter unit. In the current models, the radiation detector is a Geiger Muller tube. The electronics provided are self sufficient: there is a fast microcontroller, a precision regulated high voltage supply, a digital counter and a network interface (Ethernet). The detector works by itself, while consuming very little power, measurements show a consumption like 0.160A @5V, that is only 0.8Watts of power! It could almost run on a single AA cell for hours, or it could easily be powered by a solar power source.

It was designed to be as plug-and-play-able as possible. It just needs a 5V DC power supply (usb/phone charger like) and a network cable to a router (it gets the IP via DHCP automatically), and that’s it: it starts transmitting data to the web portal. On the map, the location of each unit is estimated automatically. This positioning system can also be overridden in configuration, in case the user wants to show a point on map closer or farther from the real geographic position.

The detector is embedded in a rugged aluminium case with a very compact size.

Three variants, A, B and C
The plan is to provide three different uRADMonitor devices, that will be part of a single, global radiation surveillance network. From simpler to more complex these are:
– Model A: a small compact detector, this device contains a Geiger counter (SBM-20 or SI-29BG), a temperature sensor and a network interface. Encased in a small aluminum box, exposing only the DC power connector and the Ethernet port, intended as a fixed monitor. It’s main advantage is the relative low production cost, while offering continuous radiation surveillance. The radiation detector is built upon a SBM-20 tube.
– Model B: the same compact size as the above, while also offering a LCD and a built in battery for remote operation. Model B can be used both as a monitor (when connected to the network via Ethernet cable) and as a mobile dosimeter showing the radiation levels on the LCD. Data is centralized only if the device is connected to the network (via the Ethernet cable).
– Model C: the most complex uRADMonitor design, features the same LCD as the previous model, but comes with more features and sensors: a GPS unit for mapping radiation data to location and also for standalone use as a GPS Tracker, a SDCard slot for logging the data when a network connection is not available, a wireless network connection to avoid installing complicated Ethernet cables – only DC power is required. Model C logs data to SDCard when Internet is not available and then uploads the data automatically when a connection becomes available. The wireless connection is standard 802.11B/G.

At the time of this article, model A is available for production. A few test variations were also produced, like the A2 model similar to the A but having an extra barometric pressure sensor. The 8 photos above show a chronological evolution of the model A, and how it evolved from the first PCBs to the final production variant (last picture).

uRADMonitor as a kit
There are some problems with offering a kit. First is the software that needs to be written in the microcontroller and then the calibration issues: currently all units part of the network have been carefully matched and calibrated to a common reference. This ensures the results are reliable and that would be an issue if distributing the detector as a kit. But maybe we can come up with something later.

Opening the network to external devices
The uRADMonitor network, composed of the monitoring stations visible on the Global Radiation portal has the advantage of similar design with reasonable calibration. All stations currently part in the network have been manually verified and calibrated against a known radioactive source.
Should the network allow input from external unknown devices, the accuracy of the data presented could be affected, because there would be no practical way of detecting errors caused by defective design or construction, or various other problems that could appear and pass undetected while feeding erroneous data to the network.
A solution that might work, is to mark the external units with a visible flag, to differentiate them from the genuine uRADMonitor units. An API could be provided for external devices to feed data to the network. Input from this units would be for reference only, and have only limited scientific value, unlike the genuine units that are able to show comparable variations from one geographic location to another thanks to their verified and controlled design.

Data traffic
The devices send small packets of data every minute. It is ok if some are lost (then those measurements will simply not reach the server). Each packet is close to 46 Bytes in size. One day (24h) will total a number of 66KB of data, this a very limited quantity that will work even on slow connections, with no impact issues on other transmissions.