[time-nuts] temperature control

WarrenS warrensjmail-one at yahoo.com
Sun Sep 18 04:23:15 UTC 2011

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

Bill Harris w7kxb at msn.com

Something to be said about "no moving parts".

> 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

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