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| # | Post Title | Result Info | Date | User | Forum |
| Answer to: How to calculate correct resistor values for an LED? | 6 Relevance | 1 year ago | Admin | Arduino | |
| The resistor value for an LED is crucial as it limits the current flowing through the LED, protecting it from damage. Choosing the right resistor value depends on the LED's specifications and the voltage of your circuit. Here's how you can calculate it: Formula- R = (Vsource - Vf) / ILed Vsource is the Arduino’s pin voltage (e.g., 5V or 3.3V). Vf is the LED’s forward voltage (e.g., ~2V for red, ~3V for blue/white). Iled is the desired current (usually 10-20mA for standard LEDs). For example, with a 5V source, a red LED (Vf = 2V), and 15mA current: R = (5V - 2V) / 0.015A = 200Ω People choose different resistor values based on: Brightness: Lower resistors (e.g., 100Ω) make LEDs brighter; higher resistors (e.g., 1kΩ) dim them. Power source: Different sources (3.3V vs. 5V) need different resistors. LED specs: Forward voltage and current ratings vary by LED. | |||||
| Answer to: Need help with the working of this circuit | 6 Relevance | 2 years ago | mertozkan | Circuits and Projects | |
| @nathan This circuit diagram is for a simple LED flashlight controlled by a push button switch. Here's how it works: 1. Power Supply: The circuit is powered by two 3V batteries connected in series, providing a total of 6V. 2. Switch: When you press the button ("Push ON"), it completes the circuit, allowing current to flow. 3. Capacitor and Diode: - The 100u capacitor is used to smooth out any voltage fluctuations, acting as a buffer to provide a steady voltage to the LED. - The 1N4148 diode prevents current from flowing back into the capacitor, ensuring that the capacitor discharges only towards the LED. 4. Resistor (100k): This resistor limits the base current going into the transistor. It ensures that the transistor is not damaged by excessive current and controls the transistor's switching action. 5. Transistor (BC547): This acts as a switch. When current flows through the 100k resistor to the transistor's base, it allows a larger current to flow from the collector to the emitter of the transistor, powering the LED. 6. LED: The "Super-bright White LED" lights up when the transistor conducts. LEDs are diodes that emit light when current flows through them in the correct direction, as indicated by the arrow in the symbol. 7. Resistor (15R): This 15-ohm resistor is connected in series with the LED to limit the current flowing through the LED, protecting it from burning out by excessive current. In summary, when the push button is pressed, it completes the circuit allowing current to flow. The current passes through the 100k resistor to the transistor's base, turning it on. This allows a larger current to flow through the transistor to the LED, lighting it up. The resistor in series with the LED ensures that only a safe amount of current flows through the LED. The diode and capacitor work together to manage the voltage and current supplied to the LED for steady operation. | |||||
