Dcf 77 Receiver & atmega8535

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 02:37 PM
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Hi,and excuse my inexperience. I would want to realize a dcfControlled-clock using a ferrite antenna to receive the Dcf signal and a atmega8535 for decode it and send the result on a display. I want to use this antenna

http://en.wikipedia.org/wiki/Fil...

From Conrad.com Part no.: 641138 - 89

I don't know if i can connect the output of the antenna directly on an Input Port of micro, of is better to interpose a ic to filter and improve the quality of signal. Could anyone give me an advice if have had an experience with dcf77 signal decoding with an atmel micro? I don't know if there are some other threads on the argument, in this case could link me them? Thank you for kindness and attention.

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AVR Microcontrollers, megaAVR and tinyAVR, ATmega8, ATmega8535
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timgoh0
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Posted by timgoh0: Sat. Jan 22, 2011 - 03:01 PM
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You will need a decent filter network after the antenna, and some sort of amplification. The DCF signal itself is relatively weak, and the Q factor of just the antenna itself might not be enough.

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MBedder
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Posted by MBedder: Sat. Jan 22, 2011 - 03:12 PM
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I would want to build a Formula 1 racing car. Please tell me if I can use the wheels of my grandma's bike and a vac motor I found in a dump. Could anyone tell me how do I assemble all this stuff together to win a next F1 championship? :D:D:D

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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MBedder
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Posted by MBedder: Sat. Jan 22, 2011 - 03:15 PM
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timgoh0 wrote:
You will need a decent filter network after the antenna, and some sort of amplification. The DCF signal itself is relatively weak, and the Q factor of just the antenna itself might not be enough.

OK, and what then? Feed this amplified signal to Mega8535 ADC? What for? Tell us the whole secret, Mr. Expert :D:D:D

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 03:18 PM
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timgoh0, thank you for reply. MdBedder,

http://videos.howstuffworks.com/...

Now you can build your formula1!

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MBedder
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Posted by MBedder: Sat. Jan 22, 2011 - 03:25 PM
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Go back to school and learn some of the very basics of electronics instead of asking such idiotic questions.

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 03:37 PM
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..I'm curios to know your preparation on basics of electronics;) My question, is just relative to a commercial module, analyzing a sequence of bit is different from build an antenna. Manifesting our excellence is not indication of knowlege..

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MBedder
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Posted by MBedder: Sat. Jan 22, 2011 - 03:41 PM
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danielfaraday wrote:
Manifesting our excellence is not indication of knowlege..

But manifesting your ignorance even isn't necessary - it's so obvious itself :D

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 03:48 PM
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If you are not interested to my ignorance, nobody oblige you to answer;) While i learn basics of electronics, learn basics of formula1, it can be useful;)

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Bronze Markdavid.prentice
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Posted by david.prentice: Sat. Jan 22, 2011 - 04:02 PM
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There is an Arduino project that reads the Receiver output signal via the ADC. So I can only assume that the module has an analog output. You could equally well use the analog comparator pin as input.

Other modules have a digital output.

Once you have a reasonably clean signal, you have to decode it. Verify with the check bits in the signal.

I would guess that you will often have errors. So if you have a free running clock, you just need to 'correct' the time whenever you get an error-free decoded DCF77 signal. e.g. just like your kitchen clock !!

David.

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MBedder
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Posted by MBedder: Sat. Jan 22, 2011 - 04:17 PM
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The point is that the OP wants to directly connect the antenna signal (not the receiver signal) to the AVR input (amplified or not - this doesn't matter):

danielfaraday wrote:
I don't know if i can connect the output of the antenna directly on an Input Port of micro, of is better to interpose a ic to filter and improve the quality of signal.

No matter that the module has a dedicated receiver on board - he wants to implement the receiver himself using Mega8535. That's why I'm happily mocking at him :D

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 04:31 PM
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MBedder, correct me if i say wrong, my aim is to learn. Considering that DCF77 is an ASK modulated signal, with a 25 % carrier reduction of 200ms every second marker for logical 1 and 100ms for logical 0, image you have an ideal square wave, you could count time the signal stay high and low and decode the bit sequence, i suppose. It's not correct?

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MBedder
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Posted by MBedder: Sat. Jan 22, 2011 - 04:35 PM
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Wrong. From the antenna you get the AM 77.5 kHz carrier frequency, not a demodulated digital signal.

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 04:35 PM
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PS i've to admit you're nice :D

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ossi
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Posted by ossi: Sat. Jan 22, 2011 - 04:39 PM
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Hi daniel,
your DCF77 module has so calle open-collector output
with a maximum current specified to be 1mA.
(I got info from CONEAD). So I think normally
the module ouput is directly fed to the ATMEL-AVR
onput with pullup-resistor enabled. You can do some software filtering of the digital signal to
detect the 0.1sec or 0.2 sec pulses. It
is normally also good to connect a LED to the
module, but due to the low current you either need a
large limiting resistor or an additional transistor.

Where are you located ? If you are too far away from the DCF transmitter it my be a roblem to receive it.

@MBedder: Better help than mock, or stay qiet.

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MBedder
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Posted by MBedder: Sat. Jan 22, 2011 - 04:47 PM
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ossi wrote:

@MBedder: Better help than mock, or stay qiet.

Jawohl, Herr Sturmbannführer! :D

Next time I promise to beg for your fucking approval first :D:D:D

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 05:01 PM
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Hi Ossi,
Thank you for your cortesy. I'm located in south italy, (Calabria), so I'm at about 1600 km from Mainflingen, i think at limit of admissibility region.

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ossi
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Posted by ossi: Sat. Jan 22, 2011 - 05:11 PM
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Do you already have the module to start with
experiments ?
Do other DCF77 based clocks work at your home ?
DCF77 reception may be disturbed by switched mode
power supplies, TV-sets, electronic fluorescent lamps
and that kind of stuff. So before actually going into
the AVR stuff I would check the reception withan oscilloscope or an LED. Quality may also depend on daytime. Probably at night you will have better
conditons.

There are some folks here with experience in long
wave DX.

Perhaps move this thread to "electronics" ?

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danielfaraday
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Posted by danielfaraday: Sat. Jan 22, 2011 - 05:17 PM
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I've a DCF77 clock and it seems to work, at evening the signal quality is better. Yes, probably "electronics" is more appropriate.

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ossi
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Posted by ossi: Sat. Jan 22, 2011 - 05:21 PM
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Here some technical info (all you ever wanted to know about DCF77 in english):

http://www.ptb.de/cms/fileadmin/...

If you have a working clock it should also be possible
to built one with a good receiver module. I have no
experience with the CONRAD module.

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timgoh0
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Posted by timgoh0: Sat. Jan 22, 2011 - 07:12 PM
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Sampling and decoding the LF timesignal is quite possible, but I've not tried specifically on the AVR. It can be done though, but I'm going to stay out of this until the trolling stops.

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ossi
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Posted by ossi: Sat. Jan 22, 2011 - 08:18 PM
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It's possible (with an AVR) to sample at 10ks/s and
work with 2.5kHz intermediate frequency. Then 10ks/s
sampling is perfect for I//Q demodulation. But that
certainly is not the road to success for a beginner.

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Bronze MarkJohanEkdahl
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Posted by JohanEkdahl: Sat. Jan 22, 2011 - 09:30 PM
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Quote:

Go back to school and learn some of the very basics of electronics instead of asking such idiotic questions.

Interesting attitude, MBedder. Why isn't learning allowed here?

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Posted by bobgardner: Sun. Jan 23, 2011 - 02:03 AM
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But Daniel Faraday is the theoretical physicist that knows how to do time travel if you have a BF magnetic field. Surely he should be able to read a time code using an RF module?!?

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