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Automatic emergency light

Bench build · Batteries and solar · Intermediate · about 30 minutes

LED lamp turns on when mains fails, charges when it returns. While the mains adapter is on, it charges the cell and holds a relay in, which keeps the lamp off. When the mains fails the relay drops out and its normally-closed contact connects the cell to the lamp.

Automatic emergency light: the finished build running on the simulator's bench

Build it in the labGuided build, test sheet and fault finding, free in your browser.

Parts list

Test procedure

Each test has an expected value and a pass range, like a factory test sheet:

  1. Mains on: lamp off
  2. Mains on: cell charging
  3. Mains fails: lamp on

How it works

What it does: LED lamp turns on when mains fails, charges when it returns.

Build it (guided or ready-made), then run its test procedure below. Every test has an expected value and a pass range, just like a factory test sheet.

Background

The rechargeable emergency lights in shops, stairwells and homes during brownouts.

More builds: batteries and solar