Resistors

 

Resistors




















Resistors in Arduino are components that oppose the flow of electrical current. Think of them like a pipe narrowing down: the narrower the pipe (higher resistance), the less water (current) can flow through.

Here's why they're used in Arduino projects and some examples:

  • Limiting Current to LEDs: LEDs (Light Emitting Diodes) are delicate components that can be damaged if too much current flows through them. A resistor placed in series (one after the other) with the LED limits the current to a safe level.

    • Example: You have an LED that needs 20mA (milliamperes) to light up properly and the Arduino output pin provides 5V (volts). Without a resistor, too much current would flow and burn out the LED. You calculate the required resistance (using Ohm's Law: Resistance = Voltage/Current) and place that value resistor in series with the LED.

  • Creating Voltage Dividers: A voltage divider uses two or more resistors in series to create a specific voltage at the point between them.

    • Example: You have a sensor that outputs a voltage between 0V and 3V, but the Arduino analog input can only handle 0V to 5V. You can use a voltage divider to scale down the sensor's output to a range of 0V to 1.5V, making it safe to read. This involves using two resistors in series; the voltage at the middle point (where the sensor is connected) is a fraction of the total voltage (5V from the Arduino), determined by the resistor values.

  • Pull-up and Pull-down Resistors: These resistors ensure that an input pin has a defined state (HIGH or LOW) when no signal is applied.

    • Example: You have a button connected to an Arduino input pin. When the button is not pressed, the pin could be floating (neither HIGH nor LOW), leading to unpredictable readings. A pull-up resistor connects the pin to 5V through a relatively high resistance (e.g., 10k ohms). Normally, the pin is HIGH. When the button is pressed, it connects the pin to ground (0V), making it LOW. Without the pull-up resistor, the pin state would be undefined when the button isn't pressed. A pull-down resistor works similarly, but connects the pin to ground, making it normally LOW.

In each case, the value of the resistor (measured in Ohms, denoted by the symbol Ω) is crucial. Different resistor values are needed for different applications. Common resistor values range from a few ohms to millions of ohms (megaohms). You select a resistor based on the voltage and current requirements of your circuit, using Ohm's Law (Voltage = Current * Resistance) to calculate the appropriate value.

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