http://www.synclab.org/?tag=raspberry%20pi

http://www.geekroo.com/products/795

Shane.

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Good point. I am a sucker for great surplus equipment too, in fact I have two rooms full of stuff most of which is used from time to time.. I envy Tom's collection. I think we need to have a "Time Nuts For Dummies" article written that takes J. Vig's writing and puts it into much less of a technically rigorous 3 to 10 page article that makes timing accessible to the average product manager or systems engineer, and adds a hole bunch of GPS Disciplining explanation as well. This should be non-academic (who cares about Leesson's formulas digested to the N'th degree when simply looking for a lab reference) and should be fun and easy to read, but still get all the important points across. bye, Said In a message dated 7/12/2014 15:01:33 Pacific Daylight Time, magnus@rubidium.dyndns.org writes: Said, ... and deprive us from cheap surplus oscillators of good performance? What where you thinking? :) But I agree fully with your point, people don't understand how their poorly speced requirements translate into cost and design-time. Accurate time to the fs for no budget is what you can expect if they push their wishlist, but they have seen the E-18 numbers in some fancy article, so as is now possible. I think not (mixing time and frequency numbers is just what you can expect among other things). Also, ADEV numbers isn't everything, it can be a splendid answer to the incomplete and incorrect asked question. Cheers, Magnus On 07/12/2014 10:44 PM, SAIDJACK@aol.com wrote: > Graham, > > I think that is the real challenge here: most folks don't know what > "precise" means for them. Timing is such a novel technology that most folks are > amazed that we are trying to get parts per trillion (or better) accuracy and > stability! > > We get customers all the time that want very precise timing, very good > phase noise, and overall very good performance but are only used to TCXO's with > maybe 10ppm frequency accuracy and cannot specify anything beyond that. > > The challenge is to explain the cost-benefit to them, like: > > 1ppm == $1 > 0.01ppm = $300 > 10ppt == $1500 > 0.1ppt == $$$ etc. > > Once dollars are mentioned, desired specifications usually are attained at > fairly quickly :) > > We recently had an inquiry that we forwarded to a major atomic oscillator > vendor, and the estimated $10 Million design cost and 10 year design time > quickly shut that idea down.. > > bye, > Said > > > In a message dated 7/12/2014 08:54:09 Pacific Daylight Time, > gh78731@gmail.com writes: > > Shane: > > The question I think that is being asked is ... > What does "precise" mean to you? > To the nearest order of magnitude, what kind of accuracy are you looking > for > on your three signals. This defines the kind of system you will need. > > This group normally aspires to the more accurate end of the scale. > > If you are doing simple time logging of some process, then you are > probably at the other end of the possible accuracy scale, and can > do things much more simply and cheaply. > > So ... > > 1 PPS: +/- 1 ns? 10 ns? 100 ns? 1 us? 10 us ? > NTP: +/- 10 ms? 100 ms? 1 second? > 10 MHz: +/- 10E-6? 10E-9? 10E-12? 10E-14? > > --- Graham > > == > > > On Sat, Jul 12, 2014 at 3:57 AM, Shane Morris <edgecomberts@gmail.com> > wrote: > >> Hal, >> >> As much as I'd like to explain the "big picture" in list, it would make > God >> awful noise - if you wish to know any details, I encourage you to respond >> to me off list. Given the fact that the robotics is so totally off topic, >> I'm not willing to discuss them here. Thats only out of respect to the >> topic of the list. The only real stipulations at this design part of the >> project is 10MHz out, 1PPS out, and NTP out. Please don't think I'm being >> narqy, I'm really not going to pollute the list with off topic chatter. I >> am more than happy to discuss off list, as and when. >> >> David, >> >> I was planning to use RaspberryPis in some part of the network, and of >> course, I must be silly, they have ethernet, and can run Real Time Linux >> (the LinuxCNC distros that have been made for control of CNC machines). > By >> the way, the whole network uses heterogeneous CPU types, I'm pretty >> agnostic to CPU type, as long as it does the job I need it to. The actual >> ethernet interface won't be as deterministic as we'd like, being chained > to >> the USB bus, but if one was not to put any other USB devices on, nor > attach >> anything that draws power, the USB performance would be good enough for >> second accuracy NTP frames. This is without any real analysis of any spec >> sheets, although I have this link: >> >> http://www.synclab.org/?tag=raspberry%20pi >> >> Thats an interesting read in and of itself. An additional link is: >> >> http://www.geekroo.com/products/795 >> >> Which is a Mini ITX motherboard for RaspberryPi, which can then go nicely >> into a 1RU case. Add LCDs and other bits and bobs as needed (I saw a nice >> little LCD with an ATMega driver taking TTY strings in the ODROID > Magazine >> earlier today - it was meant for an ODROID, but it will work with > anything >> that'll output VT100 codes). Once in an 1RU case, it looks neat, and > would >> work just as well as a $500 NTP ethernet time source second hand off > eBay, >> if not much more configurable and hackable. >> >> Many thanks for the thoughts! >> >> Shane. >> >> >> On Sat, Jul 12, 2014 at 5:50 PM, Hal Murray <hmurray@megapathdsl.net> >> wrote: >> >>> >> > edgecomberts@gmail.com said: >>>> I am needing a GPS source of precise time, in three flavours - 10MHz >> (or >>>> so), 1PPS, and ethernet NTP. In the beginning, the NTP will be most >>> > important, and as time goes on, I'll need the 1PPS signal. >>> ... >>>> If a static CW12-TIM ethernet clock could be made, I would be willing >> to >>> try >>>> my hand at mounting them to mobile robots, again, for synchronised >>> timing of >>>> events. >>> >>> I'm missing the big picture. Are the robots the end target? What are >> you >>> going to do before that? >>> >>> Do the robots have a network connection? (maybe only WiFi to a local > PC >> > controlling them) >>> >>> How accurately do the robots have to be synchronized? >>> >>> >>> -- >> > These are my opinions. I hate spam. >>> >> > >>> >>> _______________________________________________ >>> 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. >>> >> _______________________________________________ >> 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. >> > _______________________________________________ > 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. > > _______________________________________________ > 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. > _______________________________________________ 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.

At 04:09 PM 7/14/2014, SAIDJACK@aol.com wrote: > >I think we need to have a "Time Nuts For Dummies" article written that >takes J. Vig's writing and puts it into much less of a technically rigorous And maybe a recommended list of simple experiments that new time-nuts can perform. -- newell N5TNL

yes you are right On 7/14/2014 2:41 PM, Scott Newell wrote: > At 04:09 PM 7/14/2014, SAIDJACK@aol.com wrote: >> >> I think we need to have a "Time Nuts For Dummies" article written that >> takes J. Vig's writing and puts it into much less of a technically >> rigorous > > And maybe a recommended list of simple experiments that new time-nuts > can perform. >

Sounds like a great idea, Maybe I can venture beyond the Raspberry Pi with NTP and PPS GPS ..how far does the rabbit hole go? Frits On 7/14/14, Scott Newell <newell+timenuts@n5tnl.com> wrote: > At 04:09 PM 7/14/2014, SAIDJACK@aol.com wrote: >> >>I think we need to have a "Time Nuts For Dummies" article written that >>takes J. Vig's writing and puts it into much less of a technically >> rigorous > > And maybe a recommended list of simple experiments that new time-nuts > can perform. > > -- > newell N5TNL > > _______________________________________________ > 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. > -- vbradio.wordpress.com

>>I think we need to have a "Time Nuts For Dummies" article written that >>takes J. Vig's writing and puts it into much less of a technically rigorous > And maybe a recommended list of simple experiments that new time-nuts > can perform. There's quite a list of resources at the main time-nuts page: http://leapsecond.com/time-nuts.htm If playing with NTP is your interest, David Taylor's site is superb: http://www.satsignal.eu/ntp/ > Maybe I can venture beyond the Raspberry Pi with NTP and PPS GPS > ..how far does the rabbit hole go? Newcomers and experimenters also enjoy the powers of ten PDF: http://leapsecond.com/ten/ /tvb

Hi As I recall from conversations with John over the years, the presentation he wrote was (for the most part) an effort to “dumb down” the subject for a more general audience … Bob On Jul 14, 2014, at 9:00 PM, Tom Van Baak <tvb@LeapSecond.com> wrote: >>> I think we need to have a "Time Nuts For Dummies" article written that >>> takes J. Vig's writing and puts it into much less of a technically rigorous > >> And maybe a recommended list of simple experiments that new time-nuts >> can perform. > > There's quite a list of resources at the main time-nuts page: > http://leapsecond.com/time-nuts.htm > > If playing with NTP is your interest, David Taylor's site is superb: > http://www.satsignal.eu/ntp/ > >> Maybe I can venture beyond the Raspberry Pi with NTP and PPS GPS >> ..how far does the rabbit hole go? > > Newcomers and experimenters also enjoy the powers of ten PDF: > http://leapsecond.com/ten/ > > /tvb > > > _______________________________________________ > 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.