Update README.md

Chapter Overview filled

README.md

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 ## Overview
 
+This project describes how I built a Geiger Mueller (GM)-counter as an IoT device. I found in an old russian GM-counter (from the days after the Chernobyl disaster) the 2 builtin GM-tubes of type SBM-20u (СБМ-20). The LCD display of this GM-counter was broken and so I decided to build a state of the art GM-counter which is integrated into my home-network. The features for my needs are:
+* a portable device for measuring radioactive (sample) materials.
+* a piezo buzzer shall indicated a gamma or beta radiation hit. It shall be possible to witch this off for long term measurements.
+* also a stationary device for doing long term measurements with for at least 2 years permanent data logging.
+* configurable WIFI access parameters.
+* a WEB server presenting the actual ionizing radiation dose and a graph of the last hour dose.
+* download of the logged data files with a format which can easily imported into LibreOffice Calc or equivalent.
+* a stabilized high voltage booster to supply the GM-tubes.
+* low power consumption and posibility to power the device over a mobile phone with an USB cable.
+
 ## Hardware
 
 ## Software
 
-## Troubleshooting
-
 ## Photos