Home Automation Circuit Diagrams

Auto Night Lamp Circuits

We usually turn ON the lights in our houses and offices manually. We need to turn ON the lights only when it is dark. So, how will that be if we make a circuit which turns ON the lights automatically when it is dark? In this article, we shall see how to automatically turns ON our domestic Auto Night Lamp Circuits when it is dark.


  • Auto Night Lamp Using High Power LED
    • Circuit Diagram of Auto Intensity Control of LED Lights
    • Working
  • Intelligent Unambiguous Night Lamp Switcher
    • How to Operate this Night Lamp Switcher Circuit?

Auto Night Lamp Using High Power LED

Auto Night Lamp Using High Power LEDs is a circuit that turns on the LED lights connected to it at night and automatically turns them off during the day. LEDs are becoming more popular every day as a result of the benefits they bring over traditional filament bulbs or fluorescent lamps. They produce a higher-quality white light with a higher intensity than others. In comparison to their counterparts, they also use less energy.

This circuit demonstrates how to regulate the light intensity of a night lamp using high-power LEDs. The light dependent resistor is the component in the circuit that detects light. The light dependent resistor’s resistance is proportional to the amount of light it receives. The resistance of the circuit lowers as the intensity of light shining on it increases. The device’s resistance increases as the intensity of light shining on it diminishes. We’re using the light dependent resistor’s property to detect light and, as a result, control the LEDs. Twenty-five light emitting diodes are arranged in an array in such a way that five LEDs are connected in series and five such series LEDs are connected in parallel.

Circuit Diagram of Auto Intensity Control of LED Lights


In saturation mode, the transistors are employed. In this mode, they serve as electronic switches. The BC547 transistor is a general-purpose NPN transistor that is utilised to switch the LEDs further. This is a heat-sink-equipped power transistor. The heat sink aids the transistor in dissipating generated heat into the atmosphere, allowing it to withstand larger power loads than it could without it.

A 12V DC power supply powers the complete circuit, including the LEDs. Typically, a battery-based DC power supply is preferred. You can, however, utilise a regulated and rectified ac power source.

The circuit makes use of high-powered white LEDs. These LEDs produce the same amount of light as a standard fluorescent bulb. The amount of light provided is adequate for reading or any other daily activities. All of the components may be neatly put on a printed circuit board, and the LEDs can be set in the correct order. To ensure that the lighting is evenly dispersed in your room, try to arrange the LEDs at a spacing of around 1 cm between them.

Intelligent Unambiguous Night Lamp Switcher

There are numerous factors to consider while creating a night lamp switcher, without which it is possible to damage home equipment and lights. Strict steps are made in this circuit to ensure that the lights to be activated are not harmed as a result of switching. In general, if we build a simple automatic night lamp switcher, the lights will turn on when it gets dark. However, there is a snag. When the darkness level approaches, the circuit may receive sequential dark and light signals with short time intervals.This may cause the circuit to repeatedly turn ON and OFF the lights at a high frequency which can possibly damage our lights within a few minutes or hours. This happens every time at evening as well as in the morning when the light intensity crosses a value for which our circuit is sensitive and toggles the switch.

This circuit is not only a simple automatic light switching circuit, but it also prevents repetitive frequent switching of the devices, which is often overlooked in similar circuits but can harm our working equipment. The lights, in this situation. This is why the circuit is dubbed “intelligent unambiguous night lamp,” because it intelligently controls the lights to avoid recurrent switching caused by ambiguity.

Circuit Diagram for Unambiguous Night Lamp Switcher

Auto Night Lamp Circuits

How to Operate this Night Lamp Switcher Circuit?

Two photo detecting devices detect two levels of intensity in the circuit. In this circuit, photosensitive devices are Light Dependant Resistors. The level of light intensity is detected using a light dependant resistor and an op-amp as a comparator. The first light intensity is produced by the U1 IC 741, while the second light intensity is detected by the U2 IC741. These two light intensities are utilised to determine when the lights should be turned on and off without sending out confusing signals.

The two light detecting modules are wired together so that when the initial light intensity (dark point 1) is detected, the circuit activates the relay, which turns on the lights. When both light detecting modules detect light, the circuit will switch the relay off again. As a result, there are no ambiguities. Simpler circuits that sense darkness and turn on the lights exist, but the majority of them fail to remove unwanted repetitive switching. This circuit performs an excellent job of removing unwanted switching effects.

The 555 IC U3 is in the bistable mode whereas the IC U4 acts as a buffer. The output of first IC 741 is given to the reset pin of the bistable IC whereas the output of second light detecting module with IC 741 is given to the set input of the bistable multivibrator.


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