Dusk-to-dawn switch (interruptor crepuscular, photocell switch)

What a dusk-to-dawn switch is

An interruptor crepuscular switches lights on automatically at dusk and off at dawn. It uses a photocell that measures ambient light: when it falls below the level you set, it closes the circuit, and when it rises again, it opens it. Nobody has to remember the garden or entrance light, and it is never left on during the day.

Types

• Built-in photocell: a single weatherproof unit fitted outdoors.
• Separate sensor: the unit sits in the board and a small sensor goes outside. The neatest option in residential buildings and business premises.
• Astronomical clock: it does not measure light but calculates sunset and sunrise from the date and location. Shadows and dirt do not affect it.

Dusk switch with a timer

Often you do not want the light on all night. The answer is to pair the dusk switch with a time switch: the light comes on at dusk and goes off, say, at midnight. On entrances, signs and façades it saves a good deal, and it helps meet the light pollution limits in Andalusia (Decree 357/2010).

Setting and installing it

• Set the switch-on light level, in lux.
• Keep the photocell away from the fittings it controls, or it will switch on and off endlessly.
• Aim it where street lights and car headlights do not reach it.
• For large loads, the dusk switch drives a relay or contactor.

Who to call

We fit dusk switches, astronomical clocks and timers for gardens, façades and residential buildings. See outdoor lighting and communal area lighting in Seville, Spain.