An inverter that has been converted into an emergency power system. This system only activates when the electricity from the mains supply is interrupted; more critically, it does not activate when power from the mains supply is available.

Fig. 1: Auto on/off circuit for inverter Can you provide me with a configuration (emergency lighting system) in which only a small number of my lights will turn on when the power from the mains is cut off, and more significantly, in which they will not turn on when the supply from the mains is available? This is the question that a reader who wanted to install an emergency lighting system in his factory posed to us when he contacted us. The first thing that came to mind was, "Why doesn't he just use an inverter?" Then, however, we came to the conclusion that a typical inverter would cause the emergency light to turn on even when there is electricity coming from the mains, which is something the reader did not require. We had to act quickly, so we tossed an old inverter and made a few alterations. We connected our specialized inverter to the line that supplied power to the emergency light he had. We were able to modify the inverter in little than two hours, and as a result, the reader was more satisfied. Now that we've made some adjustments, we'd want to go ahead and share them with you in the event that it makes our readers even happier. This straightforward circuit can be implemented as an auto-on/auto-off switch in any residential inverter, provided that the inverter's output load is known. Utilize a relay that has a higher current rating if you need to handle a heavier load.