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System design document

A project log for Team TAHMO

Develop robust and affordable advanced sensing capability for 20,000 weather stations in Africa (lightning, precip water, ...)

Nick van de GiesenNick van de Giesen 08/11/2015 at 04:360 Comments

The system consists of four parts:

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

system_diagram.png

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.

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