[time-nuts] help

[Chris Albertson]

On Sun, May 1, 2016 at 12:26 PM, Bill Baker via time-nuts <
time-nuts at febo.com> wrote:

> My problem:  I'd like some kind of off-the-shelf device that can take the
> time code and switch on or impulse another circuit-- specifically  I'd like
> to trigger a 180 year-old fog bell (I'm a lighthouse nut as well,
> www.henryisland.com) on the hour and maybe be able to impulse my minute
> school clocks.  I'm not at this group's technical level, so it's got to be
> pretty easy to program. So I need a box that I can program with SMPTE time
> in and a timed switch impulse out.  Any ideas?


I assume you only need to be accurate to within about 1/10th of a second or
so.  Any general purpose computer like and old PC can do this but today
you'd go with a Raspberry Pi 2 or some other single board computer.   The
first step is to keep the computer's internal clock in sync with your time
signal (NTP can do that and NTP will likely already be installed on the
computer)  then if the computer is running a Unix-like OS (such as Linux,
BSD or Mac OS X) there is a table you can set up that will run various apps
at certain scheduled times.   You'd simply set s cron tab entry to blow the
horn on every hour every hour.   Not much software to write as this kind of
stuff (syncing to an external clock and doing things on a schedule) is
built in to the OS.

OK if you need to be much more accurate it gets harder but really this is a
audio alarm and the speed of sound is very slow such that the delay you'd
experience from sending 100 feet from the fog bell is longer than the delay
introduced by the software

So yjr only thing you need is to write software that does just one thing,
ring the bell then quit and let "crond" call it based on entries from the
table.

I see suggestion to use an Arduino or the like and program it.  That could
work too but if the little computer is powerful enough to run a unix-lil OS
you save some effort because they already come with built-in utilities to
do things on a schulue and to stay sync'd with an external clock signal.
-- 

Chris Albertson
Redondo Beach, California