Freezing consumer Sonoff (Shelly1) to -20C - Page 1
Forum section: electronics / beginners

author: cybermaus
author_rank: Frequent Contributor
timestamp: October 29, 2019, 09:33:00 am
content: ​HiWe have about 15 Shelly1 devices, a EU build and hopefully slightly better quality of Sonoff IoT devicesThey are used to control lights on a Campground, day/night etc.We want to turn off the entire camping circuit lights for the winter, but it can get -15, sometimes even -20 Celsius at night.I wonder if there is any expectations or knowledge about this. Will the solder joints or electrolytic capacitors suffer?Obviously it would it be better keeping them powered, turning off the lights by software, using the standby current of maybe 1W to keep the device slight above surroundings. I've read about theoretical "tin-pest" on modern lead-free. And I guess electrolyte can eventually freeze, though with all the chemicals in there, its probably way lower then 0 Celsius.But I really rather turn off the entire circuit, anyone has any actual experience in this, for either Shelly specific, or on modern lead-free solder joints or electrolytic capacitors?Thanks

author: Rigolon
author_rank: Regular Contributor
timestamp: October 29, 2019, 11:20:20 am
content: Well I can't say much about the solder joints. I live in a tropical region so temperature usually is not an issue.But electrolytic capacitors usually work on very low temperatures -40°C or -55°C are pretty common.In this cases you could always search for the datasheet of the equipment or contact the manufacture.But their manual already specifies that the Shelly1 can work from -40 to +40°C

author: MagicSmoker
author_rank: Super Contributor
timestamp: October 29, 2019, 12:08:05 pm
content: In my experience, the two big things to watch out for at low temperatures are, indeed, the ESR of electrolytic capacitors (which goes up - sometimes dramatically - once temperature drops below 5C or so) and clock crystals ceasing to oscillate, even at temperatures within the range allowed by the datasheet.There's not much you can do about the former except make sure the circuit can tolerate the higher ESR (and note this is somewhat self-correcting if there is a reasonable amount of ripple current present - the higher ESR causes more internal heating) while for the latter I've resorted to placing a 0.5W resistor sized to draw about 0.25W from the power supply in close proximity to the crystal to keep it warmer than the ambient.I'm not familiar with a Sonoff Shelly1, but if it is a consumer-grade electronics device then I wouldn't count on it to actually perform reliably across a wide environmental range (temp and humidity).

author: cybermaus
author_rank: Frequent Contributor
timestamp: October 29, 2019, 02:35:29 pm
content: Quote from: Rigolon on October 29, 2019, 11:20:20 amWork temp, yes. But Storage temp?I suspect the listed -40C is ambient temperature. With the device using a little standby, suspect it stays nicely warm, well above -13C "tin-rot" temp.But when turned off the entire winter?In fact,this shows someextra expected internal temps while running.Note how it is not listing low temps, and in fact seems to assume standby temp is 15C higher then ambient.But, maybe you are right. If they list -40C ambient, and also list while standby it may be internally 15~20 higher, then it should be capable of -20C when turned off.Oh well, maybe I should just try and see how many are still alive come summer.