[time-nuts] temperature control

EWKehren at aol.com EWKehren at aol.com
Sun Sep 18 01:22:30 UTC 2011

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

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