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资源说明：Single board for bento-Geigie v3.0
## bGeigie3 These are the Eagle CAD files for the bGeigie v3.0 (codename NX) board. This project is a part of the Safecast radiation monitoring project. Find out more on [the Safecast website](http://www.safecast.org) _Note_: although the github repo is named `bGeigie2`, the content is really the **bGeigie3**. ## License 2011-2013 (c) Robin Scheibler Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) For more details see (http://creativecommons.org/licenses/by-sa/3.0/) ## Produce a bGeigie3 ### Gerber The gerber files can be downloaded [here](https://dl.dropboxusercontent.com/u/78009186/files/bGeigie_v3.4_gerber.zip) ### BOM The full BOM can be found [here](https://docs.google.com/spreadsheet/ccc?key=0AvXZ3hGhBSusdEQ3NjlfN2hRUnljeTNhNEF5WDNzVWc&usp=sharing). ### Software * [Firmware](https://github.com/Safecast/SafecastBGeigie) * [Modded arduino IDE](https://github.com/fakufaku/Arduino) [bin](https://github.com/downloads/fakufaku/Arduino/arduino-Safecast-20121019-macosx.zip) * [Automated programming tools](https://github.com/Safecast/SCbG3-hexes) ## Tech notes ### Power supply The system is powered by a LiPo battery providing 4.2V at full charge and dies around 3.5V. ### Battery sensing The Atmega1284p has two internal analog references: 1.1 or 2.56. We need to sense the battery voltage between 4.2 and 3.5V. Let's use a voltage divider with R1 = 100K and R2 = 120K. Then `Vs = R2/(R1+R2) = 0.54*Vin`, giving a range of 2.3V to 1.89V roughly. We decide to use the 2.5 reference. This gives use roughly 170 levels of resolution. ### 50 Ohm trace for the Radio and GPS antennas * Wiki entry on [microstrips](http://en.wikipedia.org/wiki/Microstrip) * Microstrip impedance [calculator](http://www.cepd.com/calculators/microstrip.htm) As a starting point, I used the following values based on [PCB Fusion](http://www.seeedstudio.com/depot/fusion-pcb-service-p-835.html?cPath=185). * Trace width: 2.815mm (need to look-up tolerance of printing service) * Substrate height: 1.6mm (standard from PCB Fusion) * Copper thickness: 0.035mm (guessed from PCB Fusion characteristics, inner layer ?) give an impedance Z=50.04 Ohms. ### Possible printing services * [PCB Fusion](http://www.seeedstudio.com/depot/fusion-pcb-service-p-835.html?cPath=185) * [PCB Cart](http://www.pcbcart.com/) (seems to offer manufacturing too) * [PCB Express](http://www.pcbexpress.com/)
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