[time-nuts] No 1 PPS output on a Tbolt

Robert Darlington rdarlington at gmail.com
Fri Feb 12 17:09:44 UTC 2010

I'm using a very bright blue LED and series resistor on the PPS output of my
thunderbolt and it's quite visible.  It's not bright by any means, but it is
distracting to see out of the corner of my eye in the rack some days.  I
like the dual color LED idea and think I'll make a similar connector for
this type of thing.  Thanks.


On Fri, Feb 12, 2010 at 5:24 AM, Peter Vince <pvince at theiet.org> wrote:

> Hi Robert,
>     I put a dual-colour (red-green) LED in a BNC plug for just this
> sort of purpose.  No series resistor - the 50-ohm source impedance
> limits the current nicely.  With dual-colour, I can see both positive
> and negative pulses.  100ms pulses are perfect, 10ms OK, 1ms are very
> dim, but there is no chance of seeing the 10us pulses from the
> Thunderbolt.
>     As others have said, I set the (analogue Tek 2445) 'scope to
> 10us/div, 2 volt/div, 50 ohms, DC positive edge trigger, and waggle
> the trigger level.  The display is dim, but visible.  A slightly
> slower scan would narrow and brighten the pulse on a tired tube.
>     TTFN,
>          Peter
> On 8 February 2010 15:15, Robert Darlington <rdarlington at gmail.com> wrote:
> > Try hooking the output to an LED.  It's very difficult for me to see the
> > pulse on my analog scopes but there is no arguing with the blinking
> light.
> >
> > -Bob
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