6 LED IN SERIES

Designing a Series Circuit of Six LEDs with a Forward Bias Voltage of 2V and Forward Current of 20mA

Introduction: In this write-up, we will explore the design and characteristics of a series circuit consisting of six Light Emitting Diodes (LEDs). The LEDs will be connected in series with a forward bias voltage of 2V and a forward current of 20mA. The power supply for this circuit will be 18V. We will discuss the implications of this configuration and analyze the key parameters involved in the circuit design.

LED Basics: LEDs are semiconductor devices that emit light when a forward voltage is applied across their terminals. They are widely used in various applications such as lighting, displays, and indicators. LEDs have several advantages, including energy efficiency, long lifespan, and compact size.

Forward Voltage and Current: Each LED has a forward voltage (Vf) and forward current (If) specification. The forward voltage is the minimum voltage required to overcome the diode's internal resistance and allow current flow. The forward current is the optimal current at which the LED operates efficiently without getting damaged.

Series Circuit Configuration: Connecting LEDs in series means that the positive terminal of one LED is connected to the negative terminal of the next LED, creating a continuous path for current flow. This configuration allows the supply voltage to be shared across all the LEDs in the series.

Design Calculation: Given that each LED has a forward voltage of 2V and a forward current of 20mA, and the total supply voltage is 18V, we need to ensure that the circuit parameters are within the safe operating range.

Voltage Calculation: Since we have six LEDs connected in series, the total forward voltage (Vt) required will be: Vt = 2V x 6 = 12V

Current Calculation: The total forward current (It) flowing through the circuit will remain constant, as it is determined by the power supply. 

Therefore: It = 20mA

Resistor Calculation: To limit the current flowing through the LEDs, a current-limiting resistor is required. Since the supply voltage (Vs) and the total forward voltage (Vt) are known, we can calculate the value of the resistor (R) using Ohm's Law:

R = (Vs - Vt) / It

= (18V - 12V) / 20mA

= 300Ω

Results and Considerations: With a forward bias voltage of 2V and forward current of 20mA, and using a 300Ω current-limiting resistor, we can create a series circuit of six LEDs with a total forward voltage requirement of 12V. The remaining 6V of the supply voltage will be dropped across the current-limiting resistor.

It is important to note that while the calculations assume idealized LED characteristics, real-world variations in the forward voltage and current of the LEDs may exist. Additionally, thermal considerations should be taken into account to prevent overheating. Therefore, it is recommended to use appropriate heat sinks or consult the datasheets of the specific LEDs for detailed specifications and guidelines.

Conclusion: Designing a series circuit with six LEDs requires careful consideration of the forward voltage, forward current, and supply voltage. By properly calculating the values of the current-limiting resistor, the circuit can be configured to ensure the safe and efficient operation of the LEDs. It is essential to pay attention to real-world variations and thermal management to ensure the longevity and optimal performance of the LEDs.