[time-nuts] temperature control

[EWKehren at aol.com]

WS
I did follow your suggestion and installed the original ATT heat  sink and 
got a base plate temperature of 47 C. Prior to that I did lower  the fan 
speed by reducing the voltage to 6 V, that increased the base plate  to 43 C 
but all vibration and noise disappeared. The only way to find out  what if any 
performance degradation occurs is with a D/M measuring A/V. Once I  have 
software for my D/M I will conduct tests with different Rb/OCXO  combinations. 
My goal remains the same, the best in long term and short term  performance 
in a GPS Rb OCXO combination.
This test was more of what can be done and the amazing part to me was how  
little moving air will make a difference. I will stay with my 5X5X1 cm 
vibration  mounted fan that sits to the side of the Rb moving air across an array 
of small  heat sinks with circular fins unless A/V tests tells me I have a 
problem. 
Bert Kehren
 
 
In a message dated 9/18/2011 12:24:04 A.M. Eastern Daylight Time,  
warrensjmail-one at yahoo.com writes:


Advantages and Trade-offs both ways
For a simple "no moving  parts" version,
Oversize the heat sink and attach a 10 Watt resistor to it  whose voltage 
is 
controlled to keep the Heat sink temperature  constant

ws
****************
Bill Harris w7kxb at  msn.com

Bert:
Something to be said about "no moving  parts".
Bill-w7kxb

*********
> From: EWKehren at  aol.com
> Date: Sat, 17 Sep 2011 21:22:30 -0400
> To: time-nuts at  febo.com
> Subject: [time-nuts] temperature control
>
>  Recent comments on dewier  flasks bring me back to test I conducted   
last
> year using a nice flask that I tested extensively using the guts  of a 
> 10811
> as a constant heat source. What I found and  reported was that the ambient
> inside changed as much as .4 C with 8 C  changes on the outside. The tests
> ended when it fell off the pedestal  that I mounted on my balcony in 
order 
> to
> take advantage of  the large overnight changes. Since then I have focused 
> on
>  temperature control by fan cooling. Shopping for small fin heat sinks I  
> ran
>  across a VGA cooling assembly at our favorite  supply site 370537089468 
> for
> a  total of $5.92. At that  price I said what the heck. It came in 4 days
> and I  mounted it  on the back of a FRS. After 4 hours without cooling, 
the
> back  plate  was 59.7 C with an ambient of 29.2. the fan assembly without 
 
> fan
> running  was actually already cooling the back  plate, because without it
> mounted, the  temperature was 62  C.  6 minutes after powering up the 12 
V 
> 80 mA
>  fan,  temperature had dropped to 45 C and 30 minutes after power up the  
> back
> plate is  40.6 C again with 29.2 ambient. The fan  is very quiet and it is
> amazing what can  be done with a small  amount of moving air. This fan 
with 
> a
> single op amp   will be able to hold the back plate within .1 C at 45 C.
> Eventually  all my  time/frequency units will have some kind of moving 
air 
>  temp.
> control. Lower  temp. will also extend life.
> Now my  dilemma is whether to use my original design with an array of 
small
>  heat sinks with the fan off the side not part of the Rb or stay with  
this
> super  simple design.
> Bert Kehren   Miami


_______________________________________________
time-nuts  mailing list -- time-nuts at febo.com
To unsubscribe, go to  
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the  instructions there.