The LED Resistor Calculator tool is designed to help you calculate the resistor value and power dissipation required in an LED circuit. Here’s a detailed explanation of each parameter in the tool and how to obtain the necessary values:

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1. Supply Voltage (V)

What is it?

The supply voltage is the voltage provided by the power source in your circuit, such as a battery, power adapter, or a regulated power supply.

How can I get it?

• If you’re using a battery, check its specifications (e.g., 9V battery or 3.7V Li-ion battery).
• If you’re using a power adapter, its voltage rating will be printed on it.
• For regulated power supplies, you set the voltage directly.

Example Values:

• A 9V battery = 9V
• USB power supply = 5V
• Li-ion battery = 3.7V

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2. LED Forward Voltage (V)

What is it?

The forward voltage of an LED is the voltage drop across the LED when it’s operating at its desired current. Different LED colors and types have different forward voltage values.

How can I get it?

• Check the LED’s datasheet or product packaging.
• Typical forward voltage values for common LEDs:
  • Red LED: 1.8–2.2V
  • Green LED: 2.0–3.0V
  • Blue LED: 3.0–3.5V
  • White LED: 3.0–3.5V

Example: If you are using a red LED, its forward voltage is typically around 1.8V.

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3. LED Current (mA)

What is it?

The LED current is the amount of current the LED needs to operate efficiently and provide the desired brightness without overheating. It is measured in milliamps (mA).

How can I get it?

• Check the LED’s datasheet or packaging.
• Common operating currents for LEDs are:
  • Standard LEDs: 20mA (0.02A)
  • High-power LEDs: 350mA or more.

Example: For most small indicator LEDs, the operating current is 20mA.

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4. Number of LEDs

What is it?

The number of LEDs refers to how many LEDs you plan to connect in your circuit. The configuration (series or parallel) affects how the total voltage and current are calculated.

How can I determine this?

• Count the number of LEDs you are using in the circuit.
• Choose the connection type:
  • Series: The total voltage is the sum of the forward voltages, and the current is the same through all LEDs.
  • Parallel: The total voltage is the same as the forward voltage of one LED, but the current is the sum of the currents through all LEDs.

Example:

• Series: 3 red LEDs = Total forward voltage 1.8V×3=5.4V1.8V \times 3 = 5.4V.
• Parallel: 3 red LEDs = Total forward voltage 1.8V1.8V, total current 20mA×3=60mA20mA \times 3 = 60mA.

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5. Connection Type (Series or Parallel)

What is it?

The connection type determines how the LEDs are wired in the circuit. It affects the total voltage and current calculations:

• Series: LEDs are connected end-to-end, so the total forward voltage is the sum of all LEDs, but the current remains constant.
• Parallel: LEDs are connected with their anodes and cathodes together, so the forward voltage is the same as one LED, but the total current is the sum of all LEDs.

How can I choose?

• Use series if your power supply can provide sufficient voltage.
• Use parallel if you need to drive multiple LEDs from a lower voltage source.

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What the Tool Displays

• Resistor Value (Ω\Omega): The calculated resistance you need to limit current in your circuit.
• Power Dissipation (W): The amount of power (heat) the resistor will dissipate. Choose a resistor with a power rating higher than this value (e.g., use a 0.5W resistor if the dissipation is 0.432W).

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Practical Notes

• Always double-check your input values to avoid incorrect calculations.
• For resistors, use the nearest standard value if the exact calculated value is unavailable.
• Ensure the resistor’s power rating is higher than the calculated dissipation to prevent overheating.

If you’d like to enhance the tool further (e.g., include support for different resistor types or provide a list of standard resistor values), let me know!