How about actual data? For the last week, the ambient outdoor temp at
this site has been between 50 (night time), and 60 (daytime). The
SiteMonitor temp inside this 18x16x10 enclosure has been like below. So
for at least this situation, it's been running between 10 and 20 degrees
above ambient. The daytime temp is probably higher because of sun exposure.
bp
<part15sbs{at}gmail{dot}com>
On 5/19/2015 6:34 AM, Chuck McCown wrote:
Back to the original question, need more data. It is a question of
physics. Jaime touched on it.
Live load.
Ambient temp.
Thermal conductivity of the enclosure.
Surface area of the enclosure.
Wind speed at coldest temp.
Thermal convection currents inside the enclosure.
Thermal conduction currents inside the enclosure.
Not trivial.
Perhaps use some transistor grease and place a rectangular type metal
plate resistor on the memory. Add a tiny bit of foil and insulation.
It would take so little energy to get the memory up into the safe
region that it could probably happen in a few seconds. As has been
mentioned, the pre-heat on boot would certainly do that. Once booted,
measure the temperature and heat or not heat. Be a fun experiment.
The memory thermal mass is so small the resistor probably would have
more thermal mass. You could get a 50 degree rise in maybe 5 seconds
with 1/4 watt if insulated properly.
*From:* Forrest Christian (List Account) <mailto:[email protected]>
*Sent:* Monday, May 18, 2015 8:09 PM
*To:* af <mailto:[email protected]>
*Subject:* [AFMUG] Enclosure low temperature
What is the lowest temperature that each of you would normally expect
to see in your enclosures?
The reason I'm asking is that I'm in the process of developing up a
few new products.
To date, all of the packetflux products are designed with components
rated -40 to +85C (I.E way cold to way hot). I'd like to retain
this rating, but I'm running into a minor snag:
For storage, I'm planning on integrating a SD card (probably microSD)
in a socket. I only need a GB or so, and SD card memory is
inexpensive at that range.
Unfortunately, all the reasonably priced SD cards are only rated down
to about -25C or -13F. which are about ~$3 in qty. "Industrial
temperature range" ones which are good down to -40C/F are available
but they add at least $30 to the cost for non-name brand, and even
more for known brands. When you're talking about a $100 end-user
price, a $30 1GB SD card seems excessive - and probably isn't even
possible if I want to meet the $100 price with some margin.
So, I'm currently playing the 'what options do I have' game. I hate
to ship a product only rated down to -25C/-13F, but I know for at
least a large chunk of my customer base they never see below this
temperature, especially when you add a watt of power dissipation in
the case with the device. Which leads me back to my original
question: What's the lowest temperature most people would expect to
see inside their enclosures.
--
*Forrest Christian* /CEO//, PacketFlux Technologies, Inc./
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
[email protected] <mailto:[email protected]> |
http://www.packetflux.com <http://www.packetflux.com/>
<http://www.linkedin.com/in/fwchristian>
<http://facebook.com/packetflux> <http://twitter.com/@packetflux>
