[time-nuts] TBolt Monitor
didier at cox.net
Mon Oct 6 01:13:02 UTC 2008
> -----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
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.
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