inexpensive, black box, GPS or NTP based TTL time capture?
Howdy,
I’ve been working for the Catalina Sky Survey for a couple of years. For many years, CSS has been one of the most productive discoverers of Near Earth Objects (NEOs), that is, of asteroids and comets that are potentially hazardous to the Earth.
As you might imagine there are numerous interesting aspects to this project, and timekeeping is one. We use Meinberg clocks and IRIG PCIe cards to capture TTL signals from the stepper motor controller of the large camera shutters to attach accurate and reasonably precise UTC time tags to each celestial search field. Our telescope control also depends on knowing the time. Etc.
I’m at the annual planetary sciences meeting (in Provo this year) and several groups have expressed interest in duplicating our setup (details of FO converters, Schmitt triggers, etc, omitted) in a “cheap black box” to quote one fellow. Lots of people contribute productively to NEO observations, including amateurs and small teams with little funding. Improving their timekeeping would help keep rocks from falling on you and your family.
Any suggestions for a minimally expensive, maximally performing such arrangement? Or alternative architectures? One group has used:
http://www.spectruminstruments.net/TM4.pdf <http://www.spectruminstruments.net/TM4.pdf>
Thoughts?
Many thanks!
Rob Seaman
University of Arizona
On Wed, 18 Oct 2017 08:47:58 -0600
Rob Seaman seaman@noao.edu wrote:
I’m at the annual planetary sciences meeting (in Provo this year) and several
groups have expressed interest in duplicating our setup (details of FO
converters, Schmitt triggers, etc, omitted) in a “cheap black box” to quote
one fellow. Lots of people contribute productively to NEO observations,
including amateurs and small teams with little funding. Improving their
timekeeping would help keep rocks from falling on you and your family.
What is this black box supposed to do? Just provide a PPS? IRIG-B?
Or does it need to have time-stamping capabilities? If so, how many
channels?
What are your time precision/accuracy requirements?
What how cheap is "cheap"? What is the volume?
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
Hello,
Might be my first post. Thanks for the group wisdom.
I did not see any pricing on the web page for http://www.spectruminstruments.net/TM4.pdf http://www.spectruminstruments.net/TM4.pdf, and the site seems to be (c) 2007 (a decade ago).
Before I contact that vendor, I’m curious about:
- any ballpark ideas on cost?
- any reason to prefer that over, say, a Jackson Labs Fury, or?
My current setup is an eBay $130 GPSDO into an repurposed video distribution amplifier, to feed HP and Tek signal generators, frequency counters, etc. I might be doing something wrong, but Lady Heather reports 63,000 (not a typo) ppb accuracy. Not awful, but nowhere near the numbers discussed on this forum. hence my interest in something else.
Thanks for considering,
Scott W7SLS
On Oct 18, 2017, at 7:47 AM, Rob Seaman seaman@noao.edu wrote:
http://www.spectruminstruments.net/TM4.pdf http://www.spectruminstruments.net/TM4.pdf
Hi
One of the big shocks shopping for some of this stuff is that the single piece price may be
5X the “volume price”. That’s not true of everybody, but it’s true of a lot of vendors. This sort
of thing does not apply only to GPSDO’s.
On top of that, we get used to buying some items for “salvage” prices that are well below
the original volume price. A GPSDO that we buy on eBay for $40 may have sold originally
for $500 in volume. The single piece price (20 or 30 years ago) could have been $3,000.
You could argue that this does not make any sense. You could also wonder how any get out
into the market with that sort of pricing. The answer may well be that if you are a large OEM
already doing a million dollars a year worth of business with the outfit, you can get a “loaner”
for evaluation.
Bob
On Oct 18, 2017, at 8:39 PM, W7SLS w7sls.scott@gmail.com wrote:
Hello,
Might be my first post. Thanks for the group wisdom.
I did not see any pricing on the web page for http://www.spectruminstruments.net/TM4.pdf http://www.spectruminstruments.net/TM4.pdf, and the site seems to be (c) 2007 (a decade ago).
Before I contact that vendor, I’m curious about:
- any ballpark ideas on cost?
- any reason to prefer that over, say, a Jackson Labs Fury, or?
My current setup is an eBay $130 GPSDO into an repurposed video distribution amplifier, to feed HP and Tek signal generators, frequency counters, etc. I might be doing something wrong, but Lady Heather reports 63,000 (not a typo) ppb accuracy. Not awful, but nowhere near the numbers discussed on this forum. hence my interest in something else.
Thanks for considering,
Scott W7SLS
On Oct 18, 2017, at 7:47 AM, Rob Seaman seaman@noao.edu wrote:
http://www.spectruminstruments.net/TM4.pdf http://www.spectruminstruments.net/TM4.pdf
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On the home brew side there are GPS receivers (Ublox Lea 6T and Lea M8T) that will time tag incoming signals to sub usec resolution . You of course need a PC/micro to configure and read the data.
Also, if you are prepared to have a Beaglebone Black in your box you can use one or both of the two Programmable Real-time Units, modules in the SOC that are completely independant of the CPU running linux, to also get sub usec resolution. Programming required.
Le 18 oct. 2017 à 17:26, Attila Kinali attila@kinali.ch a écrit :
On Wed, 18 Oct 2017 08:47:58 -0600
Rob Seaman seaman@noao.edu wrote:
I’m at the annual planetary sciences meeting (in Provo this year) and several
groups have expressed interest in duplicating our setup (details of FO
converters, Schmitt triggers, etc, omitted) in a “cheap black box” to quote
one fellow. Lots of people contribute productively to NEO observations,
including amateurs and small teams with little funding. Improving their
timekeeping would help keep rocks from falling on you and your family.
What is this black box supposed to do? Just provide a PPS? IRIG-B?
Or does it need to have time-stamping capabilities? If so, how many
channels?
What are your time precision/accuracy requirements?
What how cheap is "cheap"? What is the volume?
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
"The power of accurate observation is commonly called cynicism by those who have not got it. »
George Bernard Shaw