[aprssig] Balloon warmth

[Earl Needham]

Be sure and research those CR123s, though. They have some interesting failure modes.

7 3
Earl


------Original Message------
From: Scott Miller
Sender: aprssig-bounces at tapr.org
To: TAPR APRS Mailing List
ReplyTo: TAPR APRS Mailing List
Subject: Re: [aprssig] Balloon warmth
Sent: Mar 24, 2010 09:26

The sodium acetate ones are heavy, though.

If I can find board space for the traces, I'm thinking of scattering a 
few big flat SMT resistors around the board.  The CR123A cells can put 
out 1500 mA continuously, so I could easily get a few watts of heat as 
needed.  I wish metal core PCBs were a little cheaper - that might help 
spread the heat around better.

Scott
N1VG

Steve Noskowicz wrote:
> 
> 
> The sealed plastic pouch versions don't use air.  It is a reversible exothermic chemical reaction.  This is the ones with the metal popple disk.
> 
> I think they have a super saturated solution of an acetate salt, perhaps sodium acetate.  There's several YouTube videos showing the process - ad nausium...
> 
> at fractions of an inch of mercury the Iron compound versions will die.
> 
> 
> -- 73, Steve, K9DCI
> 
> 
> --- On Wed, 3/24/10, Scott Miller <scott at opentrac.org> wrote:
> 
>> About a dozen people have suggested
>> this, but I'm not convinced the oxygen level is
>> sufficient.  I do happen to have a vacuum chamber in
>> the shop, so once I get a functioning payload again I'll
>> have to throw a few of those in there and compare the heat
>> generated to a control at 1 atmosphere.
>> 
>> Scott
>> N1VG
>> 
>> AD4BL wrote:
>> > An alternative to keeping equipment warm on a balloon
>> flight is to use the hand warmers.   They
>> last about
>> > 8 hours and provide enough heat to keep equipment
>> operating in a cold environment.
>> > 
>> 
>> 
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> 
> 
>       
> 
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> 


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KD5XB -- Earl Needham
http://groups.yahoo.com/group/cw_bugs
Quoting from the Coast Guard: ZUT
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