Night Active Relay. Utility Gadgets .13

Now you can light your home premises with this Automatic lamp. It turns on in the evening and turns off in the morning. No switch and no manual operation. So it can light the premises even if the inmates are not in home. A simple security measure.

1. Transformer power supply is used for the circuit.

2. LDR is used as light sensor. Its resistance is very high in dark

3. During day light, LDR conducts and ground the base of T1 so it will be off. Relay remains de energized.

4. When the day light decreases in the evening, resistance of LDR increases and T1 gets base bias and conducts. This activates the relay and lamp turns on. This condition retains till morning.

5. Capacitor C1 is added for the clean switching of relay. T1 will conduct only when C2 is fully charged. Otherwise relay will click during the light transition.

6. Relay is used connect the load such as Bulb, CFL or Tube light. Three to four CFL can be connected to the relay.

7. Light from lamp should not fall on LDR.

8. Keep the unit in a place where day light is available.

9. Adjust VR1 to set the sensitivity of LDR to turn the lamp on at the particular light level in the evening.

4 responses to “Night Active Relay. Utility Gadgets .13

  1. Nice circuit, I was trying to make such circuit from 3 years but never started building. Can you make it with transformer less power supply ???

    • Hello Abishai
      Thansformerless power supply will not give sufficient current to drive relay. So transformer is necessary. If Triac is used, it can be directly connected to mains.

    • Triac cannot be used for driving CFL because of the circuit inside the CFL. It will flicker and damage easily. Triac can be used for bulbs but due to energy efficiency, people think of CFL