Hi I have installed a number of PCBs (approx 50) with an Atmega162 taking time of day from a DS1337 and displaying this on 7 segment displays.
The RTC is backed up by a lithium cell battery (CR2032) to store the time when the unit is powered off/power failure.
Everything was working fine with no problems until a few of the more recent installations seems to be loosing the time.
These are all installed in a location where a power failure is simulated once a week and a backup generator kicks in.
Does it sound likely that there is something in the gererator supply that the chips may not be used in the usual mains supply (230VAC 50 HZ) like a spike or harmonic?
The power supply on the PCB is transformer to approx 15 V then rectified in a chip and 5 V regulator to give 5VDC.
Or another reason could be the more than usual frequency of power off/on. I have seen this in an installation before that turned off automatically every night and on in the morning, seemed to drain the battery very quickly. To get around this i programed the chip to swich on and start at 0900 each morning.
Planning to go to the installation tomorrow but would be interested to hear anybodys thoughts as to what else may be the problem...