Between spontaneous reboots and false alarms, the device that I'm testing has been quite noisy lately. The false alarms were caused by a variety of voltage or current spikes at either pump start-up or shut-off. Now these are all on event counters, so a spike will result in a small event count and a problem will have a large count. It is much quieter already.

The power grid has also been rather noisy too resulting in the monitor rebooting at random times of the day. Or, was it a power problem? For now, the watchdog register's initial value is being reported to the WellNow app in place of one of the other monitored values. Most of the time it was reporting that the power was indeed the culprit, but sometimes it was the watchdog timer causing the reboot. Eventually, I found that it re-setting the time after a power outage was causing the watchdog to time-out. Changing the clock would cause the next watchdog refresh to be delayed. I've chosen to set the watchdog timeout interval to a bit over two minutes rather than invoke the refresh sequence when the clock is changed.

Fixing the power problem may be a bit trickier. First, I tried adding a 220uF capacitor to the 5V input. That worked for all of about three hours. Ok, 1000uF. Within a few days, "Beeeep!". Another power glitch reboot. Fine, 3300uF, but no more. It's been silent for about a week, but a better solution is needed. I'm going to increase the input voltage a bit. No, I'm not. The MCP1700 that is installed in my prototype has a 6V maximum input. Well, there is the MCP1703, same footprint and can handle 16V. But increasing the voltage to a linear regulator will increase the power dissipated by the regulator, and in a SOT-23 case, there is only a little leeway. There is just enough, though. On a hot day, it will be a warm chip, but well within parameters. Time to order some more parts...