Team TAHMO

At the start of the project, we included the idea to include a high-precision consumer grade GPS receiver. The idea was not just that it could provide synchronized time stamps for the lightning sensors but also could say something about atmospheric moisture content. The technology has been around for some time but until now required relatively expensive ($50,000) geoscientific ground stations. Consumer-grade GPS receivers have improved so much over the past decade that we can achieve sufficient accuracy to determine precipitable water content of the atmospheric column. The only problem is that they only detect one frequency whereas one would like to receive two frequencies in order to correct for ionospheric delays. By regionally modeling the ionosphere using a few existing geoscientific ground stations in the region, we could get by with consumer GPS receivers alone. This idea, to be implemented around Lake Victoria, has won not one but two prizes in the European Satellite Navigation Competition 2015. We won both the special prize for academia (71 entries) but also the national entry for the Netherlands. A summary of the project idea can be found here. A more compelte description is available here.

This map shows the present TAHMO stations around Lake Victoria, which will be used to install the lightning sensors and GPS receivers.

TAHMO has been selected as a winning team of the Global Resilience Challenge! Out of nearly 500 applications submitted, the TAHMO team was selected as one of eight winning teams. The Global Resilience Challenge is a multi-stage design competition designed to surface transformative resilience solutions to problems that threaten the lives and livelihoods of the most vulnerable populations in the Sahel, Horn of Africa and South and Southeast Asia.

TAHMO will now receive funding to implement the proposed solution in a way that can be scaled and adopted by others in the future. The solution proposed focuses on installing an automated climate observation system, with emergency weather warnings being provided to farmers, fishermen, and the citizens of Uganda.

From a Hackaday point of view, this means that the work we did over the last months will actually be used in the field within the coming year!

For more information on this exciting announcement, visit TAHMO.org

As this is a very first attempt at 3D printing, the results are quite nice. We used a Da Vinci Junior 1.0A that uses PLA for its prints. The first time, the two halves of the box fitted nicely, as did all the 'innards' of the box. Some minor modifications will be needed to make the assemblage of the complete box a bit easier but in general the shape is there.

The image shows the built in PCB with ThunderClick and battery holder. The GPS is fitted in the top part of the housing, on which there is a slot for the small solar cell. This first try warped a little bit but later today we hope to receive a black version, to make the solar cell less conspicuous, from a professional printer. The dimensions are 11x11x5cm.

Over the course of this project, we have learned to use quite a number of software packages and platforms. We preferred to use free online tools or, at least, free tools to ensure that any person with an internet connection could use it. Here follows a brief overview with associated newbie remarks.

GitHub

We want to share all our code and GitHub is undoubtedly the best platform to use. To make the different types of code available is an easy way, we have a small wiki page (https://github.com/nvandegiesen/Team_TAHMO/wiki). GitHub is not 100% intuitive if you expect simply a big 'synchronize' button between a local and remote repository. Instead, one first has to copy the new file into the local repository, then push, then commit. It is still not so clear why you would want to push something you do not want to commit. Still, after a while, it provides a liberating feeling that all versions are under control.

Codebender

Being able to code Arduinos on any computer connected to the internet, including a Chromebook, is a very attractive feature of codebender.cc. What is also very helpful is its very broad support for all Arduino types and derived variations, as well as bootloader installation capacity. It also has a very large library, or set of libraries, built in. There is a possibility to clone projects but we have not really explored its capacity to co-develop online or its version control.

Titanpad

For the final code development, which required interaction between different programmers in different countries, use was made of titanpad.com (https://titanpad.com/ep/pad/view/ro.qU4XtrbbJRu/rev.585). One has to explicitly copy new code into the window and it has a neat time slider to follow the development.

Fritzing

For the electronic circuit/PCB design, we used Fritzing. According to some, the continuous present of Fritzing is Fritzinging but that seems a bit over the top. The main attraction of Fritzing is that it allows schematized representation of breadboards. One can then move to a formal schematization and PCB design, including production of Gerber files. In the end, we did not use the breadboard part and there are probably handier ways to design a PCB, but the final result was very satisfying.

OpenSCAD

For the design of the housing, we used OpenSCAD, which is a fully parametric 3D design tool. As is stated by the authors, it is not so much meant to make pretty things but functional technical designs. The learning curve is relatively short and one quickly is able to build serious designs. OpenSCAD exports .stl files, which can directly be used by most 3D printers. For one prototype, we used the very affordable Da Vinci Junior 1.0A 3D printer, which used XYZware to drive the printer. Importing .stl files and printing, including supports etc., was a seamless experience.

There are two objectives we need to reach before Monday, September 21st 1:50 PDT. The first objective is finalizing the code modules that communicate with the lightning sensor, the GPS and the outside worlh through the SDI12 protocol. Four hackers are working on that, two in Nigeria, one in Uganda, and one in Kenya. The second objective is the design and construction of the housing. Nadine Rodewijk has designed the housing in OpenSCAD. The PCB designed earlier will be placed veritically, the GPS will be attached to the top of the housing, and the batteries will be placed at the bottom. The image shows the design of the bottom part. The design will be 3D rpinted over the weekend to ensure we are ready before the deadline... Files will be shared through our GitHub repository (https://github.com/nvandegiesen/Team_TAHMO/wiki).

It has taken some time to organize for the semi-final activities but we have built up the necessary steam for the final stretch. First coding task was implementation of the hardware interrupt on the ATMega328. Gilbert finished and tested the code this week. When a lightning strike (or disturber) is detected, the microcontroller wakes up, and continues to monitor until no event has occurred for ten minutes, after which it goes back to sleep. The code can be found at: https://codebender.cc/sketch:130427 .

After further and final testing, the settings of the AS3935 lightning detector has to be changed in such a way that it will only cause an interrupt when a lightning strike is detected, and not when a disturber or excessive noise is detected.

To test whether the small IXYS solar panel would provide sufficient power, we ran the power supply for a week. The load was a simple diode with 330 Ohm resistor, taking 5mA at 3.3V Vcc. The results suggest that the supply is ample, especially because the average power consumption of the detector will be much less (< 1 mA).

In the final design, we may still want to go for a more advanced solution. This solar energy harvester solution has been adopted by Decagon for its next generation weather stations and would work nicely here as well. The voltage regulator, lp2950, was chosen for its efficiency but sometimes gives off higher voltages than 3.3V, up to 4.5V, while operatiing withing the specified current range. Any suggestions as to why would be very welcome.

The requirements for the quarter final are, in addition to the first stage requirements:

Link to the video:

Update and add detail to info entered at the Entry Round stage: Done

Show at least four (4) Project Log updates: Done

Link to any repositories (e.g., Github): https://github.com/nvandegiesen/Team_TAHMO/wiki

Post a system design document, including a preliminary components list. The system design document should show what is working and what the Participant is building toward: See blog post 'System design document':
https://hackaday.io/project/5842-team-tahmo/log/22469-system-design-document

Document all open-source licenses and permissions as well as any applicable third-party licenses/restrictions: See blog post 'System design document':
https://hackaday.io/project/5842-team-tahmo/log/22469-system-design-document

The system consists of four parts:

• Power supply
• AS3935 Thunder click
• ATMega328
• NEA-M8T GPS Drotek

The AS3935 Thunder click and the NEA-M8T GPS Drotek are off-the-shelve PCBs. As these involves RF designs, we decided to go ahead with these solution under the motto “do not solve a problem that has been solved before”. In the final design, we may integrate these PCBs in our own design to save costs. There is an open source design for the AS3935 by Tautic (http://wiki.tautic.com/Category:AS3935_Lightning_Sensor_Dev_Board).

All parts have been tested but the integrated design, hardware and software, not yet. The ATMega328 provides the intelligence to the system but is asleep most of the time. The AS3935 will be in listening mode most of the time, taking 60 muA at 3.3V. Once lightning is detected, an interrupt wakes up the ATMega328, which starts a timer and wakes up the GPS. The data (energy and time stamp) are sent to the TAHMO station through a SDI12 connection.

Power supply

The power supply is relatively straightforward and is based on a design by Jon Viduchic (http://tahmo.org/going-solar-with-tahmo-stations/). We are running a small duration test with the load being a LED and 330 Ohm resistor (15 mW) running on the board. The solar panel is 4cm x 3.5cm.

AS3935 Thunder click

Communication on the new PCB between the ATMega328 and the 'AS3935 Thunder click' has been tested. The led needs to be removed to save energy.

ATMega328

PCB with ATMega has been tested with 'AS3935 Thunder click'.

NEA-M8T GPS Drotek

Communication with GPS has been tested before but not yet putting it to sleep and waking the GPS.

NEXT STEPS

• The software still needs to be integrated according to the flowchart below:

• The SDI12 connectivity needs to be implemented and tested. Code is available at https://github.com/StroudCenter/Arduino-SDI-12/wiki
• A PCB is never perfect so there will be some differences with the next batch. The latest design, and all earlier versions, can be found at the GitHub repository (https://github.com/nvandegiesen/Team_TAHMO/wiki).
• An important PCB improvement is to have a tx/tr connection instead of only the SDI12 connection. This makes on-board debugging and software updates much simpler.
• Housing! We need to make this innocuous, raintight, and affordable.

LICENSES

For the 2015 Hackaday, all licences and permissions have to be documented. In our case, that is relatively simple.

All software is built as open source software under a GNU Lesser General Public License, by others or us. The code is written as Arduino code and all code built by others is recognized as such. We use Codebender as development environment.

The designs are freely available through our GitHub repository (see https://github.com/nvandegiesen/Team_TAHMO/wiki). We used Fritzing for our design.

The PCBs have arrived. There are actually two manufacturers. The first one was OSH Park (oshpark.com), the purple one in the image below. Because of the 17 August deadline, we needed to expedite the order. Including shipping, it took about one week. The combination of watching the Hackaday Shenzhen movie and an ad on Fritzing, made us decide to also order a set of five at PCBWay (http://www.pcbway.com/), the green one in the image below. PCBWay took, in expedited form, five days to deliver and the costs were comparable to OSH Park. In general, it was nice to receive them, them being the first ever PCBs designed by us. It is a bit of a kick to design a PCB with Frizting, sending out some files, and then seeing that all the parts fit perfectly. Life is not always that way...

PCBWay gives a bit more flexibility in how many PCBs, the quality etc. They have a project page that has a bit the Hackaday look. They also show you the progess along the 14 productions steps, see below.