Our refrigerator must run at +5C during all times. But one day, the security relay of the house flipped and cut the power off. The power outage lasted 6 hours, and the temperature within the refrigerator rose to +15C. To avoid this in the future, I decided to build a mains power alarm, so I can take action if the power relay flips again.
|Figure 1. Mains Power Alarm.|
|Figure 2. PSU and metal box.|
The metal box in figure 2 measures 125 mm x 80 mm x 50 mm. The blue relay is taped to the wall.
|Figure 3. Front view.|
Figure 3 remarks. Labels are in the Danish language.
ALARM TIL means "Alarm is on".
LYSNET OK means "Mains Ok".
73 from OZ1BXM Lars