[time-nuts] HP5065A digital clock info
EWKehren at aol.com
EWKehren at aol.com
Wed Sep 28 19:29:14 UTC 2011
The one you describe is the one I use with my 5313's, would be nice to see
how they do it, they must inject the 60 and 600 Hz further up. I do not see
how they can set the second digits at 60 Hz they would scroll awful fast.
I use a 555 but at 3 Hz, 60 Hz and about 1 KHz. My counter counts down to
1 Hz but can be preset by Tbolt or a thumb wheel device and also has a hold
function. That chip family is definitely intended for accurate 1 sec.
clocks and combining dividing,synchronizing and setting is not trivial. A PIC
could do it,but I do not have the skills.
Bert
In a message dated 9/28/2011 3:05:51 P.M. Eastern Daylight Time,
eb at telight.com writes:
Yes Bert, the "three-board" type uses the counting scheme that you
described, but the other type is as I described. On the "two-board"
version the "set" mode is permanent, and there is no external counter
or logic. The 555 is a normally a one-shot for stretching the narrow
1 PPS pulses from the Rb system, but oscillates at around 60 or 600
Hz (precision not important) during setting, accomplishing the same
result. I think this design is the later one - someone at HP may have
had a "eureka" moment and realized that this simpler approach could
eliminate a board full of logic.
Ed
In a message dated 9/27/2011 9:10:25 P.M. Eastern Standard Time,
<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>EWKehren at
aol.com writes:
Sorry Ed you are wrong. Hp generates a 65 Hz signal that advances the
internal prescaler 49 counts and uses the 1 pps output to stop the 65 Hz
output at count 49 and waits for the internal 1 pps to go to 50 and
advance the
second digit one count. Sounds crazy but it works, makes the clock advance
in perfect sync with the internal second generator.
Bert Kehren
In a message dated 9/27/2011 8:16:43 P.M. Eastern Standard Time,
<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>eb at
telight.com writes:
After looking at the manual, I realized that I did look at this
series of parts way back, but didn't get the connection because I
thought it would have to be a type that takes 1 Hz input rather than
50/60 Hz. I see now that they were used in the "set" mode, bypassing
the internal divide by 50/60.
The clock module I have is the type with a 555 used as a one-shot for
normal operation, or as an oscillator for fast setting. I think this
is probably the newer of the designs, since it is simpler.
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