This circuit automatically adjusts the brightness of a lamp according to the intensity of the surrounding light. A sensor measures the total surrounding brightness and the lamp's
light intensity is controlled in the opposite direction. When the surrounding light is much brighter than usual (as regulated through the pot P1) the circuit dims the lamp. On the other
hand, when the surrounding light is darker than usual, the circuit increases the current supply to the lamp increasing its light intensity. This negative feedback regulation technique
ensures a relatively constant overall room illumination.
The sensor used in this circuit is an OPL100. It has a photodiode and an integrated regulator. The regulation control is passed on to the actual lamp circuit through an optocoupler
that provides the necessary electric and galvanic isolation. This optocoupler technique is very important to increase the safety level of the circuit. Potentiometer P1 provides
manual brightness adjustment.
Follow safety precautions in constructing this device. Insulate all high voltage lines properly. Use insulating box to house the circuit. The triac must be heatsinked and insulated properly.
Parts Placement Layout
External Wiring Layout
Electronic Circuits volume 1.0 - Circuit Nr. 29
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.