AVR-Chat

John,

Here in the States our National Institute of Standards and Technology 
(NIST, formerly NBS) provides several standard time/frequency 
transmissions for use in time keeping and frequency standardization.  We 
use a receiver/comparator to calibrate clock oscillators in frequency 
counters.  I suspect that you have a similar service provided by the 
government down yonder.  There is also a service available for world 
timekeeping but I don't know anything about it.  Here are some links:

                http://tf.nist.gov/service/its.htm
                http://tf.nist.gov/timefreq/general/links.htm
                http://www.worldtime.com/

Our NIST transmits a standard frequency signal as well as time code 
information.  I believe some of these were replaced by LORAN-C for a 
while but it appears those are now being replaced with GPS decoders.  
LORAN was the predecessor to GPS for global positioning and still may be 
used by ships at sea.

If your customer has internet access it might be just as easy to have 
his main computer collect the time information via the internet and then 
send that to your equipment.

Your temperature data is going to be a real bear.  You might think about 
sucking outside air in through an insulated duct of some sort so that 
you don't have to compensate for local thermal masses that will skew 
your readings.  If you want to add some additional spiff, you could add 
humidity since all you need at this point is one more sensor.


REB


John Samperi wrote:

>G'day all
>
>I'm looking into a project for an outdoor time/temp/date giant
>display (20" high possibly).
>
>As the unit will be mounted on the side a multistory building as
>I understand, I don't think the client will want to get a cherry
>picker or climb a window washing lift to reset the time twice a
>year to cater for the dreaded daylight time changes.
>
>So I'm looking at 3 options:
>
>1) Have the display connected to a computer which will be always
>on with a small application that will send time and date out every
>minute to the display via an RS485 link. This would take care of the
>daylight saving automatically.
>
>2) Have a plug in keypad somewhere at ground level.
>
>3) Best option-have an off air time and date signal like the one
>on my PVR. I know that in some parts of the world you can get this
>kind of signal but from my research it seems to be giving way to
>GPS time signal.
>
>So my question is has anyone used some kind of receiver that is
>dedicated to simply receive this kind of signal? Any experience?
>
>Also as far as temperature reading is concerned, a simple temperature
>chip on the PCB may not work because the air temp inside the case would
>be much higher than the actual air temp. Again any hints on this? I'm
>thinking along the lines of a small box with lots of holes and a temp
>chip inside that may work well. Again I don't have any experience with
>outdoor temp measurements so any guidance would be appreciated.
>
>Of course I may not get the job but the research is interesting. :-)
>
>
>Regards
>
>John Samperi
>
>********************************************************
>Ampertronics Pty. Ltd.
>11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
>Tel. (02) 9674-6495       Fax (02) 9674-8745
>Email: john@ampertronics.com.au
>Website  http://www.ampertronics.com.au
>*Electronic Design * Custom Products * Contract Assembly
>********************************************************
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