Just to add a couple random thoughts here... 1) Part of my concern is not knowing the cold failure modes. If you attempt to write to a card when it's cold do you destroy the card? Or does getting too cold by itself cause data loss. If I knew for instance that as long as I didn't write to the card below say -10F, I just would read a temperature sensor near the card.
2) I hate heaters. However, there's about 1W dissipated in the new product, so there is some internal heating. -forrest On Mon, May 18, 2015 at 9:52 PM, Forrest Christian (List Account) < [email protected]> wrote: > Let me explain it this way: > > Because I'm worried about the reliability of the SD card, I'm not likely > to prevent basic operation and general operation if it fails. There's > going to be sufficient memory otherwise for the device to run and operate > correctly. > > The purpose of the additional memory is for various large data storage. > An example would be if this hardware made it into a site monitor Base unit, > being able to keep all of the firmware images for all of the expansion > module types on the SD card. The unit would then pull from there (much > faster) to upgrade expansion modules in a fraction of the time. Another > example would be supporting email notifications for events - i.e. the > temperature is too cold. Without that functionality, the enhanced > features would not be available. More applicable to the current design, > there's been some requests for on-device logging of enough data so that > certain values would have historical graphs. And so on. > > This thread is definitely giving me a lot of things to think about... > > -forrest > > > On Mon, May 18, 2015 at 8:40 PM, Ken Hohhof <[email protected]> wrote: > >> I would agree with George’s numbers. Some of our smaller enclosures >> don’t have much thermal mass or internal heating. With the crazy weather >> extremes, we could conceivably get down to –25F inside the box for a day, >> especially the ones we purposely put on the north side of a grain bin to >> shield them from the summer sun. >> >> My question would be, what happens if it gets that cold? Lose some >> data? Lose the firmware? Permanently damage the device? I could live >> with some data loss as a result of a record temperature day. But I >> wouldn’t want to go out and replace a failed unit when it’s that cold. >> >> *From:* George Skorup <[email protected]> >> *Sent:* Monday, May 18, 2015 9:32 PM >> *To:* [email protected] >> *Subject:* Re: [AFMUG] Enclosure low temperature >> >> This winter was pretty cold. For about a week straight in the middle of >> January and again in February, I had a few base units reporting under 0F >> every night. And I know the outside air temp was -20 to -25F. Obviously >> take the base unit's temp reading with a grain of salt because it's clearly >> generating some internal heat. I would bet inside the enclosures it was >> easily -15F. But I think your -13F is probably OK. >> >> On 5/18/2015 9:09 PM, Forrest Christian (List Account) wrote: >> >> 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] | http://www.packetflux.com >> <http://www.linkedin.com/in/fwchristian> >> <http://facebook.com/packetflux> <http://twitter.com/@packetflux> >> >> >> > > > -- > *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* > Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 > [email protected] | http://www.packetflux.com > <http://www.linkedin.com/in/fwchristian> <http://facebook.com/packetflux> > <http://twitter.com/@packetflux> > > -- *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 [email protected] | http://www.packetflux.com <http://www.linkedin.com/in/fwchristian> <http://facebook.com/packetflux> <http://twitter.com/@packetflux>
