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Rojony Khatun
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Małgorzata Koperska, MD Steven Wooding
Last updated: September 19, 2025

Auto Night Light On-Off Circuit Using IRFZ44N MOSFET

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10K Fixed Resistor

10K Variable Resistor

Adjustable resistor with 10,000 ohm resistance

IRFZ44N MOSFET

IRFZ44N MOSFET

N-channel power MOSFET, Vds 55V, Id 49A, Rds(on) ~0.032Ω, used for switching high-current loads efficiently in electronics projects and motor control circuits

LDR (light-dependent resistor)

LDR (light-dependent resistor)

A resistor whose resistance decreases with increasing incident light intensity; also called a photoresistor

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Auto night light on-off Circuit

Simple auto night light on-off circuit using IRFZ44N MOSFET. Automatically turns lights on at night and off during the day with efficient control.

MOSFET night lamp circuit

Electronic Switch An auto night light circuit based on IRFZ44N MOSFET is an electronic switch that will automatically switch lights on at night and off during the day. The LDR sensor measures the obscurity of light, and the MOSFET is used as a switch to manage the load. This installation saves manual operation, and it is an efficient way of saving energy.

automatic light switch circuit

The IRFZ44N device of the auto night light on-off is a cheap and stable solution to turn on and off the lamps. It employs a Light Dependent Resistor (LDR) to detect the light in the environment. The LDR resistance decreases when there is an availability of daylight, the MOSFET is maintained off, and the light remains off. The LDR resistance is further boosted at night, and this activates the IRFZ44N MOSFET to turn on the lamp. This is an easy-to-construct and simple circuit that conserves energy and operates at 12V DC via the lamps or LED lights. It is a great solution to use outdoors in the garden lights, street lamp, or night lights in rooms that do not require hand control.

Work / Installation (Inputs → Outputs)

The circuit then joins an LDR and biasing resistors to sense daylight. The signal activates the IRFZ44N MOSFET, which is a low-loss electronic switch. It will be fed with a 12 V DC supply through the MOSFET to the lamp, the output. MOSFET is in the off state, and therefore, the lamp is off during the day. The lamp is automatically turned on by the MOSFET at night. It is easy to install: the LDR should be connected to the control pin, the power supply to the input, and the lamp to the output.

Testing & Final Adjustments

Once the circuit of the auto night light on-off is assembled with the components of IRFZ44N, switch it on by covering and uncovering the LDR. When it is daytime, the lamp should not be on. When it becomes dark, the lamp must switch on immediately. Tune the resistor that is linked to the LDR to adjust its sensitivity. In case the switch in the circuit occurs too soon or too late, adjust the resistor values to achieve a better performance. Make sure that IRFZ44N is properly heat-dissipated if the load in the circuit draws high current. Lastly, attach the LDR in a position where it would detect the natural light directly and ensure that it is not affected by the rain or dust to last long.

Frequently Asked Questions - Auto night light on-off Circuit:

What is an auto night light circuit?

It is a circuit that automatically turns lights on at night and off during the day using an LDR sensor.

Why use IRFZ44N MOSFET in this circuit?

IRFZ44N is a high-current MOSFET that works efficiently as an electronic switch with low losses.

What voltage does this circuit use?

It typically works on 12V DC for LED or small lamps.

Can this circuit control AC lights?

Yes, but it requires a relay or triac driver stage for AC load switching.

How to adjust sensitivity of the circuit?

By changing the resistor value connected with the LDR, you can set light sensitivity.

Does it save electricity?

Yes, the light turns on only at night and off during the day, reducing energy waste.

Where can this circuit be used?

In garden lights, street lamps, outdoor security lights, or room night lamps.

Is the circuit safe to use?

Yes, it is safe for low-voltage DC loads. For AC loads, use proper isolation with relays.

What is the load capacity of IRFZ44N?

IRFZ44N can handle up to 49A at 55V, but cooling is required for high loads.

Can I use a different MOSFET instead of IRFZ44N?

Yes, other N-channel MOSFETs with similar ratings can be used as replacements.

Rojony Khatun

Rojony Khatun

CalculatorToolsProject

Rojony Khatun is the creator of a free online tools website designed to simplify everyday and engineering-related calculations for students, professionals, and hobbyists. The platform offers a wide variety of basic and advanced calculators across key categories, including Electrical Calculators, Electronic Calculators, and Time & Date Calculators, helping users solve problems quickly and accurately.