[time-nuts] GPS DO Alternatives
albertson.chris at gmail.com
Sun Dec 9 01:56:27 UTC 2012
So the goal then is automate the process, not to make it better. I figure
once you have an easy-to-modify and easy-to-replicate design up and running
then with many people able to experiment the performance will improve.
You can almost not count the cost of the Arduino. This is a self contained
part that can be used in many projects. Same with a 12VDC power supply.
Lots of people like to play with these and have them already.
So,.... as for performance, let's just say for not that it only has to
work as well as one could do by hand and eye and a 'scope. Let's say 10E-8
What if I use a flip flop. The PPS from the GPS connects to the "set"
input of the FF and also to the Arduino interrupt. The output of the OCXO
goes to the reset pin of the same FF.
The interrupt handler reads the value of the FF. It will be either 1 or 0
depending if the phase of the OCXO leads or lags the phase of the PPS. The
software will try to keep the FF average value at exactly 0.500
On Sat, Dec 8, 2012 at 4:25 PM, Bob Camp <lists at rtty.us> wrote:
> A standard that is good to "8 digits" can be done manually. That's far
> cheaper than your goal and the software is totally open source. It can be
> done with off the shelf parts and no wiring at all.
> Problem solved?
> I suspect not….
> On Dec 8, 2012, at 1:59 PM, Chris Albertson <albertson.chris at gmail.com>
> > On Sat, Dec 8, 2012 at 9:30 AM, <johncroos at aol.com> wrote:
> >> Hello all -
> >> "People talk about good deals on Thunderbolts but I have
> >> yet to see one. It seems peak Thunderbolt passed before I was
> >> seriously looking."
> >> *The box you put it in - suspending it above the bench on inspirational
> >> thought probably
> >> will not work. A nice box is easily $ 50.00 so who cares about adding
> >> another flip flop or
> >> counter at 25 cents each.
> > The goal, well my goal is to build a GPSDO to this set of requirements
> > 1) well under 1/2 the cost of the t-bolt.
> > 2) can be made with common parts and skills most people have
> > 3) is completely modifiable (open source software)
> > So #1 above means you use a low cost box, perhaps the case and old CDROM
> > was once housed in or maybe you gut and old PC chassis
> > #2 pretty much means you have to keep theparts cound way down. Yes a
> > might cost only $1 but as soon as you get more then about three of those
> > cent cips you need a PCB. PCB making is not a common everyday skill so
> > means a way-low parts count
> > #3 means the uP is gong to have to come with a very easy to use and free
> > open source toolchain. Adruino is like that, there are others, but a
> > uP chip is not going to work
> > You are right that one way to engineer a product is to first set
> > performance numbers. But another more common way is to first identify a
> > target customer and then set a target price. In this case the target
> > customer is a hobbyist with only basic skills who wants a low cost easy
> > build GPSDO that has can understand and modify himself.
> > Next with those very hard to meet requirements (low cost, low parts
> > simple to build) we can ask if the exected perfomance is "good enough"
> > What is good enough. I'd say if you could use the GPSDO a a local
> > frequency standard for a counter that has 8 digits you are doing "well
> > enough". If you can get to 10 digital it is pretty good
> > --
> > Chris Albertson
> > Redondo Beach, California
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