[time-nuts] Announcing the TAPR "FatPPS" Pulse Stretcher
John Ackermann N8UR
jra at febo.com
Mon Jan 8 09:44:12 EST 2007
Normand Martel wrote:
> I've made a such pulse stretcher to render the 1ms
> pulse from a CMC Superstar and the 10µS pulse from a
> Trimble Lassen SK8 visible via an L.E.D. by using a
> simple 555 timer configured in a monostable fashion.
> Sure it is not nanosecond precise and i'm not sure AT
> ALL it will react to a 20ns pulse, but for a visual
> monitoring, it is perfect (pulse stretched to about
Hi Normand --
I don't know of anyone who actually *has* to deal with a 20ns pulse, but
it was interesting to see what the chip could do. I actually tested
down to 8ns and it worked there, but I like to be a bit conservative
when quoting performance.
The main raison d'etre for the FatPPS is to deal with the typically 20us
pulse width that comes from HP clocks. That's just a bit too short to
reliably trigger a serial port. I also wanted to be able to easily turn
a negative-going RS-232 pulse (which is what comes out of the Z3801A
after the "standard" RS-232 modification) into a positive going pulse to
feed the high-resolution Soekris net4501 time server.
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