LCD-LED Display

LED Lamp Dimmer Circuit

In this project, I will guide you through creating a straightforward LED lamp dimmer circuit using readily available components. This circuit allows the LED to softly brighten, reaching its peak intensity before gradually dimming, and then repeating the cycle. The core of the circuit is built around the LM358 operational amplifier IC.


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


One of the key benefits of LEDs compared to traditional light bulbs is their ease of control, allowing for rapid adjustments in brightness. While you might have experience with light dimmers, this LED Lamp Dimmer Circuit is a relatively straightforward setup in which a cluster of LEDs continuously modulates their intensity.

With slight modifications in power dissipation, you can adapt this circuit to accommodate high-power LEDs for real-time applications.

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 integrated circuit (IC) comprises two separate high-gain operational amplifiers, which are frequency-compensated and capable of functioning across a broad range of voltage levels derived from a single power source. It is operational when the voltage difference between the two supplies falls within the range of 3 V to 32 V (or 3 V to 26 V for the LM2904). Additionally, it is possible to operate this IC with split supplies, provided that Vcc is at least 1.5 V greater than the input common-mode voltage. Importantly, the low current consumption remains consistent, regardless of the magnitude of the supply voltage.


A three-terminal electronic device is employed to enhance feeble input signals. This device combines two PN junction diodes to create a transistor. Transistors come in various types, including bipolar junction transistors, field-effect transistors, and phototransistors. They find their primary utility in electrical devices due to their compact size and lightweight design.


LED stands for Light Emitting Diode, which is a semiconductor device. When an LED is powered with electricity, electrons combine with holes, resulting in the emission of light energy. LEDs are available in a wide range of colors, including red, orange, amber, yellow, green, blue, and white. Additionally, LEDs are now produced in visible, ultraviolet, and infrared wavelengths, and they are known for their exceptional brightness.

Working of LED Lamp Dimmer Circuit

The LM358 primarily consists of a package housing two independent high-gain operational amplifiers. A significant advantage of this IC is that it doesn’t necessitate individual power supplies for each comparator, as long as the power supply range is sufficiently broad. The LM358 has versatile applications, such as serving as a transducer amplifier or a DC gain block.

Notably, the LM358 IC boasts a substantial DC voltage gain of 100dB. In terms of power supply, it can function within the range of 3 to 32 volts, whereas in a split power supply configuration, it operates effectively within the 1.5 to 16-volt range. Additionally, it can accommodate high output voltage levels.

Pin Configuration of IC LM358Pin Configuration of IC LM358

In this circuit configuration, an operational amplifier (op-amp) is employed to generate a triangular waveform. The LED’s behavior is characterized by a gradual onset of illumination due to the triangular wave, followed by a gradual dimming, and this cycle repeats multiple times.

As depicted in the provided diagram, each independent op-amp within the package possesses two input pins and one output pin. The input terminals of the second op-amp are pin 2 (negative) and pin 3 (positive). Pin 3 is used for positive input when needed, while pin 2 is employed for negative feedback purposes. The op-amp remains in a non-feedback state when it receives no feedback.

When the voltage at pin 2, designated as the negative input, surpasses the voltage at pin 3, the positive input, the output tends toward its maximum positive level. Conversely, if there’s a slight elevation in voltage at the negative pin compared to the positive pin of the op-amp, the output shifts towards its maximum negative value. This inherent feature of op-amp design renders it well-suited for level detection applications.

In level detection, we apply the voltage level we wish to detect to one of the input pins and a reference voltage to the other. In our specific circuit, we connect the voltage to be detected to the positive pin (pin 3) and a reference voltage to the negative pin.

When the input voltage at the positive pin exceeds the voltage at the negative pin, the output quickly rises to its maximum positive level and remains there until the input voltage falls below the detection threshold.

This circuit capitalizes on the same principle. Resistor R5 and capacitor C1 serve as the timing components. The state of pin 3 oscillates between high and low states based on the charging and discharging of the capacitor within the circuit, while pin 2 of the op-amp functions as the reference for the desired output. Transistor T1 functions as a signal amplifier to drive the LED, and resistor R6 acts as a current limiter, safeguarding the LED from potential damage due to excessive current.


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