LCD-LED Display

LED Lamp Dimmer Circuit

I’ll teach you how to make a simple LED lamp dimmer circuit with very basic components in this project. The LED gently shines with increasing brightness in this circuit, and after reaching its maximum brightness, the LED gradually dims its brightness, and the process continues. The LM358 operational amplifier IC serves as the circuit’s foundation.


  • Introduction
  • LED Lamp Dimmer Circuit Diagram
  • Circuit Components
  • Component Description
  • Working of LED Lamp Dimmer Circuit


One of the most significant advantages of LEDs over traditional light bulbs is their ability to be readily controlled, i.e. their intensity may be quickly changed. You may have used light dimmers before, but this LED Lamp Dimmer Circuit is a relatively basic circuit in which a group of LEDs changes their strength continually.

You can also build this circuit with high-power LEDs for real-time use by making minor changes to the power dissipation.

LED Lamp Dimmer Circuit Diagram

LED Lamp Dimmer

Circuit Components

  • IC LM358 (IC1) – 1
  • Transistor BC547 (T1) – 1
  • Resistors (R1, R2) 4.7KΩ – 2
  • Resistor (R3) 22KΩ – 1
  • Resistor (R4) 10KΩ – 1
  • Resistor (R5) 4.7MΩ – 1
  • Resistor (R6) 100Ω – 1
  • Capacitor (C1) 0.47µF – 1
  • LEDs – 3
  • 9V Battery
  • Breadboard
  • Connecting Wires

Component Description


This IC is made up of two independent, high-gain, frequency-compensated operational amplifiers that can run over a wide variety of voltages from a single source. If the difference between the two supplies is 3 V to 32 V (3 V to 26 V for the LM2904) and Vcc is at least 1.5 V more positive than the input common-mode voltage, operation from split supplies is also conceivable. The low supply-current drain is unaffected by supply voltage magnitude.


To amplify weak input signals, a three-terminal electronic gadget is used. Two PN junction diodes are joined together to form a transistor. Bipolar junction transistors, Field effect transistors, and photo transistors are all examples of transistors. Because of their small size and light weight, they are primarily used in electrical machines.


Light Emitting Diode is the abbreviation for Light Emitting Diode. It consists of a semiconductor device. When electricity is supplied to an LED, electrons mix with holes, releasing energy in the form of light. Red, Orange, Amber, Yellow, Green, Blue, and White are just a few of the hues available in LED. LEDs now come in visible, ultraviolet, and infrared wavelengths, and they have a great brightness.

Working of LED Lamp Dimmer Circuit

The LM358 is primarily made up of a package that contains two independent high-gain operational amplifiers. The most important feature of this IC is that we do not need to provide individual power supplies for each comparator till the power supply range is large enough. The LM358 can be used as a transducer amplifier or a DC gain block, among other things.

The LM358 IC has a high DC voltage gain of 100db. When it comes to the power supply, this IC may operate between 3 and 32 volts, while the twin power supply operates between 1.5 and 16 volts. Furthermore, it can support a high output voltage.

Pin Configuration of IC LM358
Pin Configuration of IC LM358

In the circuit described here, an op-amp is utilised to generate a triangular wave. The LED only begins to glow slowly and brightens as a result of the triangular wave, after which it slowly turns off and gradually brightens again. Many times, the same cycle repeats itself.

As indicated in the diagram above, each independent op-amp in the package has two input pins and one output pin. The op-two amp’s input terminals are pin 2, which is a negative pin, and pin 3, which is a positive pin. If positive input is desired, pin 3 is used, and if negative feedback is desired, pin 2 is used. When the op-amp receives no feedback, it is at that state.

When the voltage at pin number 2, which is a negative input pin, is higher when compared with the voltage at pin 3 i.e. a positive pin, then the output will be received towards maximum positive voltage while if there is a slight boost at the negative pin of the op-amp as compared with the positive pin of the op-amp than the output moves in the direction of the negative maximum. This feature of op-amp design makes it ideal for use in level detection.

The voltage level that we want to detect is applied to one of the input pins, while the voltage that we want to detect is applied to the other. In our circuit, a voltage is connected to the positive pin (pin 3) and the voltage to be detected is applied to the negative pin.

When the input voltage to the positive pin is somewhat higher than the voltage to the negative pin, the output rapidly mounts to the positive maximum and remains there until the input voltage falls below the level to be detected.

This circuit also employs the same phenomenon. Resistor R5 and capacitor C1 are employed for the timing component. The state of pin 3 changes from high to low depending on the charging and discharging of the capacitor in the circuit, and pin 2 of the op-amp acquires the desired output as a reference to it. Transistor T1 is used as a signal amplifier in the circuit to drive the LED, while resistor R6 is utilised as a current limiter to protect the LED from damage caused by high current.


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