[time-nuts] TBolt Monitor

Neville Michie namichie at gmail.com
Mon Oct 6 02:25:13 UTC 2008


Hi Didier,
a time (GPS) and date display would be excellent, the only really  
useful enhancement might be a
60th second output, one pulse per minute. That would enable quite a  
few useful timing functions
in conjunction with the PPS signal. Outputting the formatted time  
data may start to get very specific to
a project, but the pulse per minute overcomes a major part of the  
problem of identifying which pulse is
which with the PPS at little cost to the project.
Neville Michie




On 06/10/2008, at 12:13 PM, Didier Juges wrote:

>
>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Neville Michie
>> Sent: Sunday, October 05, 2008 5:20 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] TBolt Monitor
>>
>> The clock displays are of two types. The analogue dials use
>> alternate negative and positive pulses and are easily
>> generated with a 0.5 Hz square wave signal. These dials are
>> either slaves from master clock systems or a cheap quartz
>> clock dial with leads to the driver coil. A totem pole driver
>> drives a capacitor that delivers the appropriate impulse to
>> the dial motor. This can be conveniently generated by a PPS
>> signal straight from the TBolt.
>> The other display is a series of decimal counters decoded to
>> produce a 60 X 60 X 24 display. This also can be driven from
>> the PPS from the TBolt.
>> The problem is setting either clock to UTC (or local time). A
>> pulse counting system can always either miss a pulse or
>> respond to a glitch to get the count out of sequence. A two
>> phase clocking system can reduce this problem but there still
>> remains the problem of start up and confidence checking.
>> The TBolt could just drive the displays directly, but loss of
>> signal or power drop-out requires a procedure to
>> resynchronise the indicators and it would be better to have
>> the displays autonomous in the absence of the GPS timing. I
>> am thinking of a TCXO to carry over the timing for long power
>> failures, that can be done with a milliwatt.
>> Leap seconds are another consideration, so what I think might
>> be most useful is a BCD seconds output from the monitor.
>> This could be jammed into the pulse counter to correct it and
>> could be decoded to give one minute pips like WWV to set an
>> analogue dial.
>> Just having a low power monitor indicating UTC is 99% of the
>> required solution.
>> All of this is the alternative to running a PC to support the
>> TBolt and so avoid the power demand and inconvenient size of the PC.
>> So what I want is a tiny black box to connect to the TBolt
>> that would indicate UTC. Constructing a micro project is no
>> problem, but the program development and installation is a
>> sticking point.
>> cheers, Neville Michie
>>
>
> Neville,
>
> All this is quite feasible, but would require more time and  
> motivation than
> I have for this at the moment.
> However, the Tbolt Monitor outputs GPS time on its display, and it  
> would be
> easy to output the time and/or date in BCD in sync with the GPS  
> packets on
> the serial port, or in an serial SPI format.
>
> I anticipate having a real PWB for the Tbolt Monitor in a month or  
> two, if
> you can wait, that will be an easy fix.
>
> Didier KO4BB
>
>
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