[time-nuts] Spectracom 8170 -> SWCC clock
jxh at jxh.com
Wed Feb 22 19:48:19 UTC 2012
On 2012/01/23 15:28, Jim Hickstein wrote:
> Reviewing the schematic for the 8170 (I'll get back to the setting coil in the
> clock a bit later), my unit does not seem to have Option 18 and A4-U4, the 8255A
> at its heart, is not populated. A pity: it would have lovely BCD outputs and an
> on-time pulse, just what I need. (The recent discussion of multiplexed 7-segment
> LED outputs tells me I don't want to try to detect ":00:00" or ":59:59" there.)
> What are the chances my EEPROMs would DTRT if I just added an 8255A to this
Looking better today. I dragged a scope up from the basement. CS is getting
hit, about 11 times, near the beginning of each second (image). I guess this
means I have to design the circuit, now, and place an order for some parts.
> What other components should I add to complete the Option 18 installation?
A3U4, the 8255A, seems to be the only thing missing, apart from A3J4, the 50-pin
header that connects to a cable to bring these BCD signals out to the rear panel
DD-50, also missing. For my purposes I can stop at the header. It'll be a nice
place to mount a little daughterboard. This is on sheet 4 of A3, the uP board
schematic, not on a separate sheet as some other options are.
> If I need different EEPROMs to enable Option 18, where could I get the image?
> (The parts and the programmer I can probably get.)
Perhaps I'll do a socket and the 8255A first, just to see the output pins move
as expected. This means paying Digikey for shipping twice. Oh, well. (Anyone
near http://www.airnav.com/airport/KMSP got an 8255A lying around? I have some
Augat 40-pin sockets left over from 1983, packrat that I am.)
Maybe I can get it done in time to have it send a pulse to the clock during
:59:59 _or_ :59:60. :-) I don't recall if an 8170 is quite that savvy, to
produce this on its output, but the BCD encoding could do it. We'll find out,
eh? And the clock will be set properly the next hour, anyway.
> On 2012/01/20 16:23, Jim Hickstein wrote:
>> I have a Spectracom 8170 in the living room (who doesn't?), and a Western Union
>> time-service clock, a.k.a SWCC clock -- a nice one, in a 3-foot-high wood case.
>> I've been watching TV with this combination for years and years but never got
>> around to feeding a pulse from the 8170 to discipline the other one. Now that
>> Western Union no longer provides the service. :-) But it just begs to be done.
>> I did draw up a TTL circuit, once (on a napkin, naturally, which I have now
>> misplaced), that could live inside the 8170. I figured out the minimum number of
>> inputs needed to detect when the MM:SS LED displays said 00:00 (for one second).
>> It would close a relay, which could feed the winding-battery power to the
>> hour-set solenoid down a pair of wires from 10 feet away. But I never built it.
>> A little over a year ago the TS clock was getting gummy and free-running slower
>> and slower, so I sent it to the clock hospital. It's back and free-running
>> nicely, so maybe it's finally time I did this. Anyone got a better idea than my
>> little TTL circuit, on a breadboard inside the 8170? I'd like to get it across
>> the rear panel without cutting a new hole, if I can avoid it. But maybe the
>> right connector would do. Another time-code receiver in the TS clock, e.g. a GPS
>> module that provides a relay closure for 1 second on the hour (if such exists)
>> might be neater. But the living room faces north.
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