View Full Version : Temperature range of BS2pe compared to OWL2pe
02-25-2010, 04:51 AM
I was just looking at the description of EME Systems OWL2pe and noticed that the temperature rating is -40 to +85 degrees Celsius. As I understand it is based of the same components (+ some additional ) as the·original BS2pe, so how comes the BS2pe rating is only between 0 and +70C?
My BS2pe went into coma when the environment temperature went down to -28C, that has happend twice this winter, so I wonder if I shall replace it with a BS2p24 instead. Hope I dont have to do too much changing of the code.
02-25-2010, 06:11 AM
SX microcontrollers have a problem with their internal 4.6V brownout reset circuit at subzero temperatures. Somewhere around -15 to -25 degC they go off into la-la land. That only occurs with the 4.6 volt brownout setting (BOR46), and that is the setting that was used on all the SX-based Stamps until recently and is still present on the BS2pe and the BS2px. Parallax has been gradually switching the modules over to an external reset circuit and disabling the SX internal brownout detector. Doing so has allowed reliable -40 degC operation of the new crop BS2e, 'sx and 'p. If you switch to the BS2p, you will have to change some timing constants (baudmodes, PULSIN etc.), and also you may have to allow for the current drain of the 'p vs the 'pe.
The OWL2pe uses the BOR26 setting instead of BOR46. That 2.6V level makes a world of difference. I have done extensive testing, some down to -60 degC. Parts on the OWL2pe are industrial parts rated for -40 degC to +85 degC operation, and the Stamp and 27LC256 memory operate fine down to 2.6 volts.
02-25-2010, 03:36 PM
OK, thanks, that really make sense.
So I guess I can expect Parallax will change the settings on the -pe and the -px soon too.
Not that the current temperature rating is a very hard problem for me, I've been using a little 12V light bulb to heat the encloser inside when I notice the -pe find it hard to keep its eyes open. And there can be many years before temperatures in our coastal climate drop down to -28C next time.
02-26-2010, 01:28 PM
Can I assume you in Norway? I think of Norway even in the coastal areas as cold, at least in comparison to what we experience here in the San Francisco bay area. Incidentally, about winter Olympic success of Norway--doing very well with 7 gold and 19 total--congratulations!! .
I have a customer in Oulu, Finland, and the OWL2pe's there do see very low temperatures down to -30 for extended periods in the sub-arctic.
02-26-2010, 04:14 PM
Oh yes, I live in mid Norway (64.00N 10.30E) but the average temp here in wintertime is just below zero, and in the·summer, perhaps some·15 degrees Celsius. This winter has been the coldest in years with·temps down to -30C for several days. Compared to·other places on the same latitude around the world (like Alaska) we are blessed with·a mild·climate, thanks to the mid atlantic Golf Stream that supplies us with hot ocean water from the Carribean areas, big affect on the scandinavian climate!
Back to topic, I know I need to re-design my weather station soon because it has almost grown out of its originally PCB. New ideas and lots of changes·has made it·look like a magpies nest! ·I have no data logging features so far so maybe it would be a good idea to re-design the whole thing and include an OWL2pe instead of the existing BS2pe. And I see the OWL is well dokumented and seems very fun to play with. (Now Moderators throw me into Sandbox I guess)
02-27-2010, 12:17 AM
No sandbox necessary; the OWL2pe is a Stamp in good standing. It has a genuine BS2pe v1.3 (32 i/o), 9 external A-D channels, 1 Mbyte of flash logging memory (AT45DB081D), and a DS1307 RTC.
That is interesting about the climate of scandinavia, and the west coastal area of Norway especially. I see where you are, not too far north of Trondheim. Here people start shivering at 10 degC, and Wiki tells me the lowest recorded temperature in San Francisco was (−3 °C) on December 11, 1932.