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README
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INTRODUCTION
------------
This library is for decoding the DCF77 time signal broadcasted
by the german PTB (Physikalisch-Technische Bundesanstalt) in Mainflingen.
I used the sample code written by Matthias Dalheimer ([email protected]) and
adapted it so that it can be used as a library in other Arduino projects.
Modified by Maciej Baur ([email protected]) to fix synced() function behavior.
To be able to use this code you have to hook up a special DCF77 receiver
to your Arduino. I used the one sold be german electronics retailer Reichelt.
Unfortunately the Reichelt module has a very weak push-pull output which
provides only around +/- 5uA.
To get usable readings out of it I used the following circuit:
____
+---|____|---+
| R3 |
____ |/c-------+------------|---o PIN2
SIG o---|____|---b| |
R1 |\e->-----+ |
| ____ |
VDD o---+-------+-------+---|---|____|---+---o +5V
_|_ _|_ _|_ | R2
D1 /_\ C1 ___ C2 ___ |
| | | |
GND o---+-------+-------+---+----------------o GND
D1: 3.9 Z-Diode
C1: 100n Ceramic Capacitor
C2: 100u Electrolytic Capacitor
R1: 120k Resistor
R2: 2.2k Resistor
R3: 10k Resistor
To amplify the signal there is a 2N2222 Transistor between R1 and PIN2.
INSTALLATION
------------
For a tutorial on how to install new libraries for use with the Arduino
development environment please refer to the following website:
http://www.arduino.cc/en/Reference/Libraries
USAGE
-----
This library assumes that you have SIG hooked up to Arduino's PIN2.
The reason for this is that most Arduino boards have two external interrupts:
numbers 0 (on digital pin 2) and 1 (on digital pin 3).
If you want to use PIN3 you would have to change the constant at the top of
Funkuhr.cpp and change the interrupt number in attachInterrupt() from 0 to 1.