[time-nuts] Scope Clock

[GandalfG8 at aol.com]

In a message dated 02/08/2007 08:48:14 GMT Daylight Time,  
robert.atkinson at genetix.com writes:
Hi Nigel & Eric,
I've just order  one of Jan's clocks. He has just got PCB's back in
stock.  I looked  quite carefully and 1PPS is standard. The board has a
PCF8563 RTC chip with a  1PPS output that is used by the microprocessor.
The signal line has a 2 pin  header that has a jumper for internal 1PPS
or you can use the header to  supply an external 1PPS.
The clock has two basic modes of operation, one  where the microprocessor
just reads the RTC and displays that time, the other  (AVR Master Clock)
where it counts the 1PPS. While in master mode it updates  the RTC to use
for reversion in case of power fail (The RTC has battery  back-up on the
board).
It looks like a great little board. The only  limitation I can see is
that the ADC's are un-buffered R/2R ladder types with  fairly high output
impedance. I want to drive a small X-Y display so I think  I will have to
build a buffer amplifier.
I'll keep the group up  dated.

----------------------

Hi Robert

I  ordered a couple the other night too:-)

I meant to report back at  the time but it was very late when I finished.

I'm also planning on  using an X-Y display, but had just assumed the inputs 
would be high impedance  and hadn't thought about buffering. Good point though 
and something I will need  to check.

One other limitation is the resolution, again something I  hadn't considered 
before ordering, so a smaller X-Y display might be a much  better option than 
the 12 inch unit I had planned on using.

These  were the comments I received from  Jan....

-------------------------------
You can use the clock on an  X-Y display, though 12” is pretty big 
(resolution of the clock is 254 by 254  pixels).

Most X-Y displays like a signal in the 0-1V range and the  hardware mod 
described in the FAQ  
(http://www.dutchtronix.com/ScopeClock2-6faq.htm#LoadResistors) will cause the  clock to generate exactly that voltage range (when using 1X 
probes or straight  cables)
-----------------------------
 
It certainly does look like a great little board, and good value too, I  
think it'll be a fun project.
Perhapst the biggest problem might be that of "little" projects growing  into 
bigger ones.....
I'm already thinking about centrally mounting an X-Y display at  the top of 
one of the racks, if I can spare the space, with clock module  built in, and 
perhaps even its own GPS module for the 1PPS:-)
 
regards
 
Nigel