Nightlight

A night light orientation (short night light ) is a lamp that emits a faint but constant light, allowing for spatial orientation in relative darkness.

Tasks and areas of

Night lights are used primarily in the area of sleeping rooms to support the orientation without any additional lighting at nighttime awakenings and getting out of bed, for example, for toileting. This is possible because at night greatly dilated the pupils and thus the eyes are very sensitive, so that even a very weak sufficient light to recognize objects and obstacles in the room. Photopic vision, ie seeing with color perception is not be given in low light, for guidance but usually not necessary. Turning on the room lighting should be avoided as a light normal strength with nocturnal dilated pupils is perceived as unpleasant dazzling, as long as no adaptation is done. Also eliminates the need to grope in the dark for the light switch, creating a risk of an accident is reduced (especially for the elderly or infirm ).

Night lights can also help to reduce the spread especially in children afraid of the dark. The fear of darkness is as Achluophobie (also: Nyktophobie ) refers. For this purpose there are night lights with child-friendly designs and shapes.

A special feature is the night lights of the emergency escape and rescue routes. In this function, night lights can be used but at best a makeshift in the private sector, as for emergency lighting in accordance with applicable building codes do not meet special formal or technical requirements, the standard night lights. In particular, an emergency lighting system of the normal power supply must be independent to ensure the function in case of power failure.

Energy supply and consumption

As a night light burns permanently or at least for long periods, low power consumption is a primary criterion for the design of the lamp and in particular the selection of the light source ( see below).

The power consumption of conventional power-saving night lights with bulbs is between 0.2 and 2 watts. At 1 watt of power and a current price of about 28 cents / kWh, electricity costs of about € 2.45 / year resulting in continuous operation ( during the day ).

If the duty cycle is reduced, energy consumption and costs are reduced accordingly. For this purpose, night lights are partially equipped with a light sensor that automatically turns on the light in the dark ( twilight switch ). Here is paying attention to the power consumption of the sensor circuit.

It can be found in commercial and night lights with motion detectors; but this is usually not meaningful, since the duration of in-house power consumption of a standard motion sensor is similar to or even greater than that of a power-saving night light.

Thanks to its low power consumption, the power supply of night lights instead of the socket can be done alternatively on batteries / rechargeable batteries. In this way, night lights can also be used for mobile use or as emergency lighting ( see above). There are light durations of a few hours in continuous operation reached ( Calculation example: a light with 0.3 W power causes it is powered from a battery with 1.5 volts a current of 200 mA, at a nominal charge the battery of 2000 mAh gives a burn time of about 10 h).

Light color

It is advantageous to use red light for orientation and night light. In darkness, the eye is a pigment ( rhodopsin ), which enhances the light sensitivity of the eye. With white light the rhodopsin is degraded in a very short time, the light sensitivity of the eye is going strong back (one is almost blind). Red light has no effect on the degradation of rhodopsin. The high sensitivity of the eye is maintained, the vision is good - albeit farbverfälscht, which is not a drawback for simple visual tasks. The above conditions are the reason why, for example, light displays are executed often red or orange at night inside a car.

Bulbs

The light source in night lights different light sources are used. The main criterion is the energy consumption.

• Glow lamps (color usually reddish- orange or green, sometimes recognizable by flickering, due to high voltage is not suitable for battery operation )
• Elektrolumineszenzstrahler, in particular LEDs (now increasingly common )
• Light bulbs with low power ( rare, since for bad light efficiency and high power consumption actually unsuitable for continuous use )
• Fluorescent lamps (rare, not available for low power )
• Tritium gas light source (very rare, needs no power supply).

• Electric lamp