RESISTORS
An introduction to resistance in an electric circuit
HOW DO THEY WORK?
WHAT DOES IT DO? As the name suggests, resistors resist the flow of electricity. The higher the value of the resistor, the more it resists, and the less electrical current will flow through it.
Unlike LEDs, resistors do not have a positive and negative lead. They can be connected either way around.
There are several types of resistors ranging from the different materials, colors, fixed or variable resistance value, the composition, structure and form.
FIXED RESISTORS These are the most commonly used resistors. These resistors have a fixed, constant electrical resistance that cannot be adjusted. There are several types: Carbon film resistors are used for applications where precise tolerance and temperature are not necessary. Metal film resistors are used for higher precision applications. Wirewound are used for high power applications.
Through-Hole
Surface-Mount
Electric Flow on Fixed Resistors
VARIABLE RESISTORS These are resistors of which the electric resistance value can be adjusted by controlling a contact (wiper) over a resistive element. They can be linear or radial.
Radial
Resistance
Less Resistance
More Resistance
Linear
APPLICATION ARDUINO
-
LED BLINK EXAMPLE
CIRCUIT
In this case, you will learn how to connect an LED and a resistor to Arduino without burning your LED bulb. Once you know how to choose the right resistor to protect your LED, you can use code provided in this example to blink your LED bulb. LetÕ s get our hands dirty!
STEP
1-
CALCULATE THE RESISTOR NEEDED
MATH TIME
COMPONENTS
A RDUIN O OR G ENUINO B OARD LED *(RED LED IN THIS EXAMPL E ) -Red LED has a voltage drop of 1.8 V and a current of abound 25m A - Arduino Pin has an output of 5V
V = (power source) - (Voltage Drop) = 5V - 1.8V = 3.2 V I = 25 mA R = V/I R = 3.2/0.025 =
STEP 2- CHOOSE THE RESISTOR
Based on the previous calculation, you need a 128 Ohm resistor , but we can use 220 Ohm instead, because...
- 220 Ohm is a standard value and is easily available.
- 128 Ohm will drive it at the maximum current which is not
desirable, since these components might have +/- 5 to 10% tolerance.
Ohm instead of 128 Ohm.
STEP 3- TRY TO BLINK LED Now you are good to go, just connect the circuit and follow the sample code below: