Simple 60 Khz Transmitter Design?

[[email protected]]

And probably more accurate than the spray can of cheese whiz in my
fridge...and about as relevant.

The 555 is the carrier.  All it has to do is stay in the bandpass of
the receiver.  So, the real question is, "what are the receiver
requirements for carrier accuracy and stability?"  I'm betting that the
$19 WWVB atomic clock hanging on my wall has a pretty sloppy receiver.

While I'm at it, let's ask one more relevant question...
WHEN does the watch update itself.  I'm just guessing that the power
consumption of the WWVB receiver might be orders of magnitude greater
than the power consumption of the part that goes tick-tock.
That suggests that the receiver might be OFF most of the time.
Won't help to have a synchronization setup that's not near
when the watch is listening.    And what if it can't find a signal?
Does it retry?  How often?  Does it ever give up and quit trying
altogether?  Battery drain may go through the roof.  Or it may just
stop trying to synchronize.
Knowledge of the update algorithm might be critical here.

When set to automatic the watch tries to update at midnight, if that
fails it tries again at 1, 2, 3, 4 and 5 AM. It will do this every
night if set to auto. You can also perform a manual receive at any
time. Battery drain is not an issue as watch is solar powered. Worth
noting the watch also a has 3 bar "receiving indicator" which I hoped
to be able to use to verify my transmission is working before I start
to encode it.

I have the oscillator running, and the scope and meter say 60.0 KHz,
which I hope would be accurate enough for reception. So far the watch
doesn't show any signal strength on the receiving indicator though.
Problem is I don't know if that means I am not successfully
transmitting anything, or that the watch is simply not seeing valid
time data...

The whole project is silly.  If you've got a wrist watch that cost over
$9.99 and needs to be set more than once a year, it's broke.  Take it
back.  If you need action on a schedule that accurate, you need
something more reliable than a human with an accurate watch
to orchestrate it.

But who among us has never delighted in a project that others
thought a waste of time?

"Need" is mentioned there a lot, I never said I "needed" to update my
watch this way. That doesn't mean I don't enjoy trying, or wouldn't
thoroughly enjoy being able to.

Sean

 

[[email protected]]

I would love it if, once you've successfully figured this out, you
would post blueprints to the design. I am curious how you are going to
send a correct time code. I found this website
http://tf.nist.gov/timefreq/stations/wwvbtimecode.htm which details
the necessary binary to code for the time. I hope that helped and I
look forward to seeing your finished product.


P.s Stop bashing the idea as unnecessary. This seems to me to be an
intellectual pursuit which has spouted from a minor dilemma. If I
understand Sean at all, he is interested more in seeing if he is
capable of solving a problem than if the product has significant
practical value.

 

[Ecnerwal]

I have the oscillator running, and the scope and meter say 60.0 KHz,
which I hope would be accurate enough for reception. So far the watch
doesn't show any signal strength on the receiving indicator though.
Problem is I don't know if that means I am not successfully
transmitting anything, or that the watch is simply not seeing valid
time data...

Probably the latter - given the nature of the time code transmission,
most things looking for it are going to look for the pattern of it, so a
carrier that does nothing would be treated as irrelevant. Speculation,
but...there's a lot of noise in that region, per multiple articles on
the subject.

You have hopefully armed yourself with a copy (free PDF download) of
NIST 960-14? it should give a good idea of what you're trying to
accomplish, and some insight on how the watch might be trying to do it.

At the risk of offending those who want everything to be perfect: if you
hang some wire off the end of your scope probe and poke it into the
middle of the transmitting coil (or near whatever you are using as an
antenna), do you get any pickup?

 

[Steven Swift]

"Need" is mentioned there a lot, I never said I "needed" to update my
watch this way. That doesn't mean I don't enjoy trying, or wouldn't
thoroughly enjoy being able to.

Sean

Okay, I see that this thread still needs an answer. I did almost exactly
what you were asking for. I use to travel to Europe a lot and I ended up
with a DCF77 radio controlled clock. Not enough signal here in Seattle to
set the clock, so I build a circuit to set the clock from a DCF77 simulator.

You can see the schematic at: http://novatech-instr.com/Fun/Dcf77.pdf

This particular clock only demodulated the time code and wouldn't show
that it was receiving anything until I had the code AND the carrier right.

I hope this meets your requirements.

Some notes:

The clock is pretty sensitive to overload, so the antenna has to be several
feet away. Also, watch out for computer monitor overloads of the signal. You
can use just about any rod as long as you can get to your resonant point.
I built this into a small plastic box using a piece of copper clad as the
board to hold the parts. Digi-Key and Mouser have 60kHz crystals.

The input on J1 is a simulated time code at TTL/CMOS levels. I used the
CD4069UB as it will run from just about any voltage from 3 to 15. Q1 is
not needed if your whole system is at 5 volts. My clock checks at
the top of each hour for time code. The drift is only a few seconds per
month, so the battery last "forever." (4-AA are even better).

I keep my DCF clock on time with this (time code comes from a GPS receiver).

Have a look at the WWVB specs to get the modulation right for your watch.

Have fun and good luck. Is this what the thread was looking for?

Steve Swift

 

[Jim Thompson]

Probably the latter - given the nature of the time code transmission,
most things looking for it are going to look for the pattern of it, so a
carrier that does nothing would be treated as irrelevant. Speculation,
but...there's a lot of noise in that region, per multiple articles on
the subject.

You have hopefully armed yourself with a copy (free PDF download) of
NIST 960-14? it should give a good idea of what you're trying to
accomplish, and some insight on how the watch might be trying to do it.

At the risk of offending those who want everything to be perfect: if you
hang some wire off the end of your scope probe and poke it into the
middle of the transmitting coil (or near whatever you are using as an
antenna), do you get any pickup?

A chip design AND the codes can be seen at...

http://analog-innovations.com/SED/WWVB-Schematic+Data.pdf

...Jim Thompson

 

[Joseph2k]

Wow, thats more like it! Can I ask for a little more guidance with C4
and L1? What sort of value should I be trying with C4? I imagine with
L1 you are saying you are wrapping 100 turns of wire around a former
of some type? Are the turns all side-by-side? What kind of rod are you
sliding into it?

I'll just order the lot from Digi-Key if I can, seems like a much more
elegant starting point than my work thus far. At least I know someone
already has this system successfully working. I may even just stick to
the DCF77 format if I can find enough information on it, as my watch
will pick up either.

I have tried a quick encoding of my signal, but no luck so far. The
watch still says it is not receiving data. I have written a small app
that creates the necessary code, then passes it off to a small square
on the monitor (flashing it white or black). This looks by my eye to
be plenty accurate enough for the 1 bit per second rate, but if it
ends up being too sloppy I'll have to come up with a more precise
method. The 555 does seem to suffer a small amount of drift though,
and if it really does need the frequency to be within a couple of Hz I
probably have no chance with it. To be honest I'm not sure how I'll
perfectly adjust this circuit either, as I can only see down to 0.1KHzwith my meter...

Sean

Poxy hell. Just how dense are you. All you were given was a crystal
controlled
oscillator, like we told you to use, and a modulator. NOT the
circuitry to generate the
modulation pattern, which we have also discussed. We are NOT saying
you cannot
do this, we have been trying to explain that it actually is a complex
piece of equipment
that you are trying to build.
Quit being so dismissive of the very good advice that you have
received here.