Emergency Exit Light

Overview

The emergency exit light is an illuminated EXIT sign carrying its own backup power so the legend stays lit through a mains failure. In normal operation it runs from the building supply while trickle-charging an onboard battery. When the supply drops, an automatic transfer circuit switches the LED string onto the battery rail within milliseconds and holds the legend illuminated for the code-required 90 minutes. The unit is mandated on egress paths by building and life-safety codes, and a periodic self-test verifies that the battery can still carry the load.

Construction

The sign is built around a two-piece Housing whose front bezel frames an edge-lit acrylic EXIT Legend Panel screen-printed with the EXIT legend; snap-in chevrons set the egress direction. Behind the legend, the LED Board carries a string of white SMD LEDs that inject light into the panel edge for even illumination.

The Control Board is the working core. It charges the pack through a constant-current charging circuit, monitors the mains, and runs the transfer/inverter stage that re-routes the LEDs to battery on power loss. A self-test button forces a battery-discharge test and a status LED reports charge and fault states. Power for the outage comes from the Backup Battery, a Li-ion pack with its own protection and balancing board sized for the 90-minute duration.

Building power lands at the AC Input terminal block, which feeds the control board through the line, neutral, and earth conductors. The Mounting Bracket bracket fixes the sign to a wall or ceiling junction box, with a canopy concealing the wiring at the mounting point.