[time-nuts] 1pps signal presence with no GPS signal.
cfmd at bredband.net
Sat Jul 9 07:40:44 EDT 2005
From: Bill Janssen <billj at ieee.org>
Subject: Re: [time-nuts] 1pps signal presence with no GPS signal.
Date: Fri, 08 Jul 2005 21:37:27 -0700
Message-ID: <42CF5487.9040206 at ieee.org>
> > 2) Have some method of bringing the drive to the LEDs out of the box,
> > so they can be replaced by LEDs on a front panel. I'd like to get the
> > 1pps LED to a front panel, but short of soldering wires onto the PCB,
> > that is not possible. I might either use a light pipe, or use the 1pps
> > output and put it into a pulse stretcher, so it can drive an LED on a
> > front panel. I'm not sure of the speed of a 555 timer, but I suspect
> > that will do the job of stretching the pulse to something that is
> > reasonable for an LED. But it would make life a lot easier if those 4
> > LEDs could be bought onto a front panel with not too much hassle.
> > David Kirkby
> Well you could use some sleeving to attach photo transistors on the existing
> LED's and use that to drive your front panel LED's. Kinda haywire but you
> don't have to modify a board. Think of it as a electronic light pipe.
Rather, think of it as an opto-coupler, with all the benefits in isolation that
a true timenut wishes to acheive.
A 50 Hz jumping into the control-loop will be above the PLLs bandwidth and will
not be steered out by the PLL, so it will go fairly undisturbed to the output.
Fortunatly, the higher frequency the higher amplitude is needed due to the
fundamental -6 dB slope of the oscillator.
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