DIY automatic light regulatorTwilight switches turn on the lights depending on the intensity of ambient light. A twilight switch can regulate illumination depending on the brightness of external light.Automatic built-in regulators maintain a specified illumination level depending on the changes in external lighting. Thus they smoothly adjust specified illumination. In this way lighting can be controlled in the streets, houses, staircases, land estates, shop windows, advertisement signs, and duty rooms of industrial facilities.Automatic light regulators save a lot of electric power. The main category of twilight switches has a photocell in its design.A photocell measures illumination. So depending on the determined value the device turns electric circuit on or off. The popular summer house sensors on solar batteries also have photocells in their designs. To be more specific, they use sensitive phototransistors or photodiodes which turn on the charging mode during the day and switch on LEDs in the nighttime.The operating principle of such device can be shown through the example of two simple assemblies which use a phototransistor and a key element on the basis of bipolar transistors. The devices come without additional up-invertors. They are powered from galvanic cells and are mounted onto small sections of the printed circuit board which facilitates assembly.The number of power elements depends exclusively on the load, i.e. on the number and capacity of LEDs. One of the devices has a regulator of actuation threshold for the LED when a certain night-time period comes.The device works from power units within the range from 3 to 9 V. Such devices are worked out very well and perfectly fit under lampshades.

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