Christmas Fairy Flashing LED Lights Circuit

With this simple Christmas light construction tutorial get ready to jingle all the way!

This circuit creates a fun and festive pattern with flashing LED lights that resemble small Christmas bulbs.

To make the lights appear even more unique one can arrange them in a string or pattern and even use various colors of bulbs.

Circuit Working:

Parts List:

There is more to this simple and affordable circuit than just Christmas celebrations.

It only consists of two resistors, a flashing LED, a tiny signal transistor such as the BC547 and many ordinary LEDs.

The remaining LEDs are controlled by the transistor which is turned ON and OFF by the flashing LED functioning as an oscillator.

A 12V unregulated mains supply can serve as the power source.

As the supply voltage and the cumulative forward voltages of the LEDs match, the LED chain does not require a current limiting resistor.

For example seven LEDs can easily be powered by a 12V source if red LEDs are used with a 1.65V voltage drop.

As a replacement use five green LEDs at 2.7V or six yellow LEDs at 2.1V each.

Another alternative is to mix colors which is an alternative to fairy lights.

Formulas:

To build a circuit that will make the LEDs flash sequentially so that it looks like a Christmas fairy.

This simple circuit design controls LEDs using resistors and a BC547 transistor.

How to Calculate Current Using LEDs:

Ensuring that the LEDs run within their safe current limitations is the most important component of the circuit.

To guarantee correct functioning each LEDs and its series resistor need to be calculated.

The formula for current flowing through an LED is as follows:

I = V_supply​ − V_LED​​ / R_LED​

where,

• Amperes or I are used to measure the LEDs current flow.
• Volts V is the unit of measurement for supply voltage.
• VLED stands for LED forward voltage for standard LEDs this is generally around 2V the datasheet provides exact information.
• The series resistors value in ohms RLED

Dissipation of Resistor Power:

Find out how much power the resistors can handle without overheating by measuring their dissipation:

P = I² × R

where,

• P is for power dissipation W watts.
• I is the resistors current measured in amperes A.
• R stands for resistance in ohms Ω.

Base Transistor the resistor:

To ensure that the BC547 transistor operates properly one have to find the base resistor.

A sufficient amount of base current IB is required to completely charge the transistor.

Formula for Base Resistor:

R_B = V_supply−V_BE / I_B

where,

• VBE or base emitter voltage is usually 0.7V for BC547 transistors.
• IC / hFE where IC is the collector current and hFE is the transistors current gain is the IB base current that is needed.

Keeping note of the specific features of the LEDs and power source, adjust the resistor values as required.

These formulas guarantee the circuits efficient and safe operation.

How to Build:

To build Christmas Fairy Flashing LED Lights Circuit follow the below mentioned steps:

Put the Base Circuit Together:

• Connect the LED that is blinking to the circuit.
• This LED are going to be used as an oscillator.
• Connect the circuit to the BC547 tiny signal transistor.
• To turn the transistor ON and OFF use the flashing LED.

Connect the regular LED String:

• Connect the transistor to the string of standard LEDs.
• By acting as a switch the transistor will turn these LEDs ON and OFF in response to the oscillation of the flashing LEDs.

Connection to the Power Supply:

• For circuit power use an unregulated 12V mains supply.
• Make sure the power supply is connected correctly.

No Limiting Resistor for Current:

• Because the supply voltage is equal to the forward voltages of the LEDs in the chain the LED chain does not need a current limiting resistor.

Choosing a Color for Standard LEDs:

• Select the number and color of standard LEDs according to their forward voltage.
• Using red LEDs with a voltage drop of 1.65V for example one can use a 12V source to power seven LEDs.
• As an alternative use the right amount for green 2.7V or yellow 2.1V LEDs.

Testing:

• After the circuit is put together turn it ON and see how the LEDs flash.
• Check to see if the LEDs are flashing as expected.

Take note:

• When working with electrical circuits always be careful and verify the connections and components.
• Consider asking an experienced person for help or consulting other sources for advice if one is unfamiliar with electronic components and circuits.

Conclusion:

By adding a PNP transistor along with to the NPN transistor the Christmas Fairy Flashing LED Lights Circuit can be modified by doing so.

Two strings of LEDs alternately flash in this form adding to the overall visual impression.

During the holiday season the Christmas Fairy Flashing LED Lights Circuit offers a DIY way to create beautiful and fascinating lighting patterns.

References:

Flashing LED String/Christmas lights to steady on [closed]