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Rojony Khatun
CalculatorToolsProjectExpert
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Małgorzata Koperska, MD Steven Wooding
Last updated: September 21, 2025

LED Blinking Circuit Using C1815 Transistor for Electronics Projects

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C1815 Transistor

C1815 Transistor

A low-power NPN bipolar junction transistor (BJT) widely used for general-purpose switching and amplification in electronic circuits.

22µF Capacitor

22µF Capacitor

Medium-value film or ceramic capacitor for AC/DC circuits

3V LED 5mm

3V LED 5mm

3V, 5mm round light-emitting diode

1K Fixed Resistor 1/4W

1K Fixed Resistor 1/4W

A 1,000-ohm resistor rated for 0.25 watts

4.7k Fixed Resistor 1/4W

4.7k Fixed Resistor 1/4W

A 4700-ohm resistor rated for 1/4 watts

1m Fixed Resistor 1/4W

1M Fixed Resistor 1/4W

A 1 megaohm fixed resistor rated at 0.25 watts (¼W), used to limit current, drop voltage, or set biasing levels in electronic circuits.

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LED Blinking Circuit using Transistor Circuit

Build a simple LED blinking circuit using C1815 transistor. Ideal for beginners and hobbyists to learn transistor switching and timing circuits.

transistor LED flasher

The LED ON/OFF is automatically switched on and off in an LED blinking circuit made with C1815 transistor. It illustrates the fundamental principles of transistor switching and timing as an introduction to electronics learning and amateur projects.

simple LED blinking DIY

The LED Blinking Circuit Using C1815 represents a very simple and easy-going project in electronics that causes an LED to turn on and off automatically. The circuit designed with the C1815 NPN transistor, some resistors, and capacitors forms a simple astable multivibrator. During power, the capacitor fills and empties, creating an ON and OFF effect on the transistor. This makes the attached LED flicker at the rate calculated by the resistor and capacitor values. When these elements are modified, they control the speed of blinking. The circuit is ideal for understanding transistor switching, timing circuits, and principles of oscillation to anyone who is interested in electronics, hobbyists, and the DIY community. It may also be extended to power various LEDs, buzzers, or small loads to create a visual or auditory effect. Components are cheap and can be built on a breadboard or PCB, and are useful as an introduction to oscillating circuits in electronics.

Work / Installation (Inputs → Outputs)

  • Power Input → 3–12V DC supply.
  • C1815 Transistor → Acts as a switch to control LED.
  • RC Network → Capacitor and resistors set the blinking frequency.
  • LED Output → Blinks ON and OFF according to transistor switching.
  • Installation → Assemble components on breadboard or PCB; connect LED with current-limiting resistor; power the circuit; adjust RC values for desired blink rate.

Testing & Final Adjustments

The DC power supply is to be connected after assembly. Automatic blinking of the LED should occur. Measure the rate of blinking and set resistors or capacitors to slow down or speed up. Make sure to confirm that the LED is poled and the C1815 transistor is positioned. Repeat Cycles should be carried out to ascertain consistency. In case of no blinking on the LED, investigate the connections of the capacitor and the resistor. Appropriate testing ensures the appropriate working LED blinking circuit that can be used in hobby projects, learning transistor switching, and testing timing circuits.

Frequently Asked Questions - LED Blinking Circuit using Transistor Circuit:

What is C1815?

It is an NPN transistor commonly used for low-power switching applications.

Can I use any LED?

Yes, standard low-current LEDs work with a suitable current-limiting resistor.

What voltage is required?

Typically 3–12V DC supply.

How to adjust blink speed?

Change the capacitor or resistor values in the RC network.

Is it beginner-friendly?

Yes, simple and inexpensive circuit for learning electronics.

Can it drive multiple LEDs?

Yes, within the current rating of the C1815 transistor.

Do I need a heatsink?

No, C1815 handles small currents without a heatsink.

Can it be used in projects?

Yes, for visual indicators, LED flashers, or hobby projects.

Is assembly difficult?

No, can be easily assembled on breadboard or PCB.

Is it cost-effective?

Yes, uses minimal and inexpensive components like C1815, resistors, and capacitors.

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.