[time-nuts] FE5680 GPS Disciplined Controller Update

EWKehren at aol.com EWKehren at aol.com
Tue Jun 24 19:50:30 UTC 2014


The response has been very positive such that a $ 45 kit is doable. Working 
 on getting at least two beta tests lined up.
However it is disappointing that no one has stepped up to tackle the  
temperature problem. how many have looked at the temperature attachment and  
clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but 
 there will be one or two orders of magnitude degradation without active 
fan  temperature control unless the internal temperature compensation is  
disabled.
I like to float an other idea I did attach a picture of the auxiliary board 
 which we also use on other projects. That board along with inductors and  
two mini circuit transformers could be added to the kit for an extra $  
8.00. Other parts are readily available. Going forward it would make sense to  
have a temperature control board and a clean up loop board. We have them but  
they are express PCB. if members would be willing to do a Gerber version I 
will  gladly work with them off list and than they could be added for an 
extra $ 4.00  to the kit.  We do not have the time. Total kit would be $ 57.00 
maybe $  55.00 including four 5 X 5 cm. boards.
Let me know what you think.
Bert Kehren
 
 
In a message dated 6/19/2014 2:56:52 P.M. Eastern Daylight Time,  
tvb at LeapSecond.com writes:


-----  Original Message ----- 
From: "Chris Albertson"  <albertson.chris at gmail.com>
To: "Discussion of precise time and  frequency measurement" 
<time-nuts at febo.com>
Sent: Thursday, June 19,  2014 8:31 AM
Subject: Re: [time-nuts] FE5680 GPS Disciplined  Controller


> I've been working in the same thing BUT I don't  want anyone who builds it
> to need a PCB.  And I want the firmware  to load over USB so there is no
> need to ship programmed chips or deal  with external programmers.   I 
think
> I can get the cost  below $20.     That said I doubt I'll get 1E-13
>  performance out of my Rb.
> 
> My little Arduino based controller  has been running now for a couple 
months
> and keeping a crystal in  lock.  The board has a pins left over for a 
serial
> port that I'll  hook up to the Rb.
> 
> The trick to getting the cost down is NOT  to do a custom PCB.  Take
> advantage of one of the uP development  boards and then for under $5 you 
get
> the USB interface, D/A and A/D,  serial ports, timers and quite a bit of
> logic all  1/3rd the size  of a credit card.
> 
> 
> On Thu, Jun 19, 2014 at 12:57 AM,  Jan Boutsen <jan.boutsen at telenet.be>
> wrote:
> 
>>  Count me in for an assembled and tested board. Great project.
>>  Jan
>>
>>
>>
>>
>> ----- Original  Message -----
>> From: <EWKehren at aol.com>
>> To:  <time-nuts at febo.com>
>> Sent: Wednesday, June 18, 2014 8:49  PM
>> Subject: [time-nuts] FE5680 GPS Disciplined  Controller
>>
>>
>>
>> FE5680 GPS  Disciplined  Controller
>> With all the FE  5680 rubidium  oscillators being used as door stops out
>> there some of us  decided  to develop a GPSDO for it. The main question 
we
>>  have:
>> Is there sufficient  interest among time nuts for a  discipline 
controller
>> for the FE5680 to make it  available?  Looking at the postings over the 
last
>> two years I am not so   sure.
>> The  construction and preliminary testing of a Brooks  Shera style GPS
>> discipline  controller for the later version  (6.81e-13 resolution) of 
the
>> FE5680
>> has been   completed. We are trying to determine the number of people 
that
>>  would be  interested in obtaining an FE5680 discipline controller (if  
there
>> is
>> sufficient  interest about $45 a kit  shipping included, $75 for an
>> assembled and tested  board,  international orders for an additional $5)
>> when
>> it  is
>> released.
>> We are also looking for three Beta   testers that would be willing to
>> purchase, assemble, and test our  Beta release  controller kit with their
>> own
>>  FE5680A and GPS receiver or Tbolt and provide  feedback. Please send  an
>> email to
>> _EWKehren at aol.com_  (mailto:EWKehren at aol.com)   Subject Time-Nuts FE 
5680A,
>>  if you would be interested in being one of the three  Beta testers. A  
key
>> requirement is the willingness to get to it right away,  the  board 
assembly
>> takes about 30 minutes. Instrumentation  to measure results is  also a
>> requirement. We obtained  impressive results using a cheap ublox 6M
>>  receiver.
>>
>> The  FE5680 GPS discipline controller  is a small (2” x 2”) board using 
8
>> DIP’s and 1  SOT23-5  package powered by +5v with 0.1” headers for all
>>  inputs
>> and outputs. Our  plan is to have the kit supplier  solder in the only 
SMD
>> device on the board. A  GPS receiver  1PPS and 10 MHz sine from the 
FE5680
>> feed the board with two  9600  baud serial ports sending TTL level tuning
>> commands to  the FE5680 and receiving  commands from and sending status  
data
>> to a
>> PC for data logging and system  control  via a simple terminal program.
>> In the chip count are  two  opto couplers that allow the use of isolated 
TTL
>> to USB  conversion. These  USB adapters are readily available and  
furnish
>> the 5 V necessary for the  secondary of the opto  circuit. An option is 
to
>> not
>> use the opto couplers  and  send the PIC TTL level RX and TX into a TTL 
to
>> RS232  adapter. Another option is  to use a TTL to RS232 converter after 
 the
>> opto couplers but then an external 5 V  source would have  to be supplied
>> for
>> the opto couplers.
>> As  I  mentioned before to get best performance from the FE5680  
temperature
>> control is  a must and after much fan and metal  work I realized that a 
Lap
>> Top heat pipe is  the easiest  lowest cost solution. Comments 
appreciated.
>> As
>> an  alternative the  temperature correction needs to be disabled.   
Otherwise
>> two control loops fight each  other.  If you  look close on page 7  of 
the
>> brochure temperature stability  from –10 to +60 C looks good but a closer
>> look
>> and you  see 4 E-11 changes over small temperature changes in the -10 to 
60
>>  C range. Extensive analysis has been done on the FE 5680 A and maybe  
some
>> one  can tackle that problem. Please look at what N5TNL  did. It is 
attached
>> and click  on his link. The FE 5680A does  have a 4 channel MAX 1246 ADC 
and
>> most likely it  is used to  monitor temperature.
>> Also  mentioned before the FE 5680  output is not the cleanest, I did
>> observe it and  some one  posted the attached. I apologize but my 
records do
>> not
>>  show who did, so  if you posted the data please come forward. For  
serious
>> applications where you  are using it as your main  reference a clean up 
like
>> the
>> Morion MV89 or HP  10811  should be considered.
>> This  addition is not  required for beta tests but temperature control 
will
>>  help.
>> I am also  enclosing the express PCB layout, be free to  use it but it 
would
>> be more  economical to do a group buy if  there is enough interest and 
some
>> one steps up  to  kit.
>> Bert  Kehren
>> To  not exceed the  attachment limit the plot will be a separate   
posting
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>  
----------------------------------------------------------------------------
>>  ----
>>
>>
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> 
> 
> 
> 
> --  
> 
> Chris Albertson
> Redondo Beach, California
>  _______________________________________________
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