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Atomic clock via a DIP

Added by JohnO about 4 years ago

Is there a schematic available for the atomic clock project?


Replies (4)

RE: Atomic clock via a DIP - Added by jcw about 4 years ago

I haven’t turned it into an official schematic, if that’s what you mean.

But my suggestion would be to simplify: use pins 3 and 4 for DATA and PON (iso pins 8 and 5), then there is no clash with the upload, and you can re-use the “standard” upload setup with just an LED + 0.1 µF cap. No need for the diodes. Change these lines and these to match, and everything else can stay as is.

Pins are a bit of a confusing issue on the LPC810, but here’s a little memory aid:

  • chip pins 1..8 are assigned as usual on any DIP-8 chip: counter-clockwise, starting from the dot
  • (G)PIO0..PIO5 are assigned in clockwise order, starting from pin 8, and skipping the 2 power pins

RE: Atomic clock via a DIP - Added by JohnO about 4 years ago

I think I figured out the wiring from the original photographs and put it together on a breadboard, here is my first output:

[dcf77]
DCF 1e2bfa MHD?
DCF 1d7764 MHD?
DCF 1d5f7e MHD?
DCF 1324b8 MHD?
DCF 128ffd MHD?
DCF 0bff7f MHD?
DCF 151963 MHD?
DCF 1e9de8 MHD?
DCF 06f6fe MHD?
DCF 1900a6 MHD?
DCF 18bcfb MHD?
DCF 1f36bf MHD?
DCF 1f33d6 MHD?

I probably still have issues with the diodes since I can’t program with all the wiring in place.

RE: Atomic clock via a DIP - Added by jcw about 4 years ago

You’re receiving data alright, else there would be no signal transitions and nothing would appear. The ones starting with “1d” look like the correct initial bits to me.

But the signal is not clean enough for error-free decoding yet. Try moving the setup to a noise-free area (attic?) or try again in the evening. Another thing which can make a big difference: rotate the ferrite/antenna coil so it is perpendicular to the direction of Frankfurt, i.e. probably slightly east of North in your area. The decoder is a simplistic one, and the UK gets a weaker signal than I do here at JeeLabs (there are considerably better decoders, as mentioned on the Blinkenlights site linked in the article). It’d be very useful to know how well this works for the UK.

Update: also, move the circuit away from your laptop, and use a USB cable with a ferrite core on one end if you have one. It’s all about noise pickup.

RE: Atomic clock via a DIP - Added by JohnO about 4 years ago

Trying to get some operation from the DCF77 hardware I loaded up the Arduino code from www.blinkenlight.net. I think it needs a very good clock source so I used a JeeNode USB which has a crystal. Indoors the activity LED is very unstable but in the semi-outdoors I can get a regular 1 second pulse on the activity LED but the code isn’t able to sync even after an hour or more.

If someone closer to Frankfurt is able to verify the Arduino sketch enclosed perhaps we can get a better understanding of the issue.

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