Christmas Fairy Flashing LED Lights Circuit

Get ready to jingle all the way with this guide to building your own Christmas lights!

This circuit uses flashing LED lights like tiny Christmas bulbs to create a fun and festive design.

You can arrange the lights in a string or pattern and even use different colors to make them look extra special.

Circuit Working:

Parts List:

This uncomplicated and cost effective circuit serves a purpose beyond just Christmas festivities.

It comprises merely two resistors, a small signal transistor like the BC547 one flashing LED and a series of regular LEDs.

The flashing LED functions as an oscillator toggling the transistor on and off, which in turn, controls the remaining LEDs.

The power source can be an unregulated 12V mains supply.

No current limiting resistor is necessary in the LED chain since the cumulative forward voltages of the LEDs match the supply voltage.

For instance, if red LEDs are employed with a 1.65V voltage drop, seven LEDs can be powered with a 12V supply.

Alternatively use six yellow LEDs 2.1V each or five green LEDs 2.7V.

Mixing colors is also an option.

Variation for Fairy Lights.

Formulas:

To build a circuit that causes the LEDs to flash sequentially to create a Christmas fairy flashing LED lights circuit.

This is a basic schematic of a circuit that controls LEDs with a BC547 transistor and resistors.

How to Determine Current Using LEDs:

Ensuring that your LEDs function within their safe current limitations is the most important aspect of your design.

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

Current via an LED formula:

I = V_supply​ − V_LED​​ / R_LED​

where,

• I is the LEDs current flow measured in amperes, A.
• Vsupply is supply voltage measured in volts V
• VLED is the LEDs forward voltage usually about 2V for ordinary LEDs, see the datasheet for exact numbers.
• Value of the series resistor in ohms Ω RLED

Resistor Power Dissipation:

Determine the power dissipation to make sure your resistors can withstand the power without overheating:

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.

Transistor Base Resistor:

You must determine the base resistor in order to guarantee proper operation of the BC547 transistor.

To saturate the transistor, there needs be enough base current IB.

Formula for Base Resistor:

R_B = V_supply−V_BE / I_B

where,

• VBE is the transistors base emitter voltage usually 0.7V for BC547
• IB Base current required (usually I_C / h_FE where, IC is the collector current and hFE is the transistors current gain).

Depending on the specific features of your LEDs and power source, change the resistor values as necessary.

These formulas guarantee the efficient and safe operation of your circuit.

How to Build:

To build Christmas Fairy Flashing LED Lights Circuit, follow these steps:

Assemble the Base Circuit:

• Connect the flashing LED to the circuit.
• This LED will serve as an oscillator.
• Connect the small signal transistor BC547 to the circuit.
• The flashing LED should be used to switch the transistor on and off.

Connect the String of Regular LEDs:

• Attach the string of regular LEDs to the transistor.
• The transistor will act as a switch, turning these LEDs on and off based on the flashing LEDs oscillation.

Power Supply Connection:

• Use an unregulated 12V mains supply to power the circuit.
• Connect the power supply appropriately.

No Current Limiting Resistor:

• Since the forward voltages of the LEDs in the chain add up to the supply voltage, no current limiting resistor is required for the LED chain.

Color Selection for Regular LEDs:

• Choose the color and quantity of regular LEDs based on their forward voltage.
• For example, if using red LEDs with a voltage drop of 1.65V you can power seven LEDs with a 12V supply.
• Alternatively, use the appropriate quantity for yellow 2.1V each or green 2.7V LEDs.

Testing:

• Once the circuit is assembled, power it up and observe the flashing pattern of the LEDs.
• Ensure that the LEDs light up as expected.

Note:

Remember to double check your connections and components and exercise caution when working with electrical circuits.

If you are not familiar with electronic components and circuits consider seeking assistance from someone with experience or consulting additional resources for guidance.

Conclusion:

To conclude, a modification can be made to the circuit by introducing a PNP transistor alongside the NPN transistor.

This variation creates alternating flashes between two strings of LEDs enhancing the overall visual effect.

The Christmas Fairy Flashing LED Lights Circuit provides a DIY solution for creating charming and dynamic lighting arrangements during the holiday season.

References:

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