Arduino #5 - Combining Resistor with LED | Resistor value calculation + Power Rating
Hello friends, welcome to the another tutorial of How to Electro. In this tutorial, we will get a basic introduction to the resistor and led along with the calculation of particular resistor value to use with an led, so that LED will work properly and have a long-life time. We will know this calculation in both the connection types namely, parallel connection and series connection. So friends, let's begin.....
Introduction
This tutorial will give us a basic introduction to the resistor and the LED along with the way of calculating the resistor value for the LED to work properly.
Resistors are useful component in electronics circuit. It helps the circuit from being broken, by providing required voltage and current to the components of the circuit. The main work of it is to provide required voltage and current to the particular components or circuit. In this way, it can uses as many ways like voltage regulator, variable voltage regulator and so on. It comes in a wide range of values having specific uses. We will know more about it in the upcoming tutorials.
LEDs are also an useful component for an circuit, as it can be used to indicate the proper working of a circuit, like power on, battery charging and so on. It can also be used as a light source by combining two or more LEDs as in a modern LED Bulb. These all has cause an increase in the use of LEDs these days. We will know more about the LEDs like its working, uses etc. in the upcoming tutorials.
Resistor Calculation
Resistor Calculation for an LED means, that , calculating the proper resistor value for an LED for the proper working of it by giving required voltage and current to the LED. We will know about the resistor calculation of a simple circuit along with series combination and parallel combination ( ways to connect LEDs ). So friends, lets start from simple circuit...Simple Circuit
The circuit consists of a battery for powering LED, a resistor and a LED. The battery used is 0f 9V and the LED used is of 1.2V, and hence the direct connection to the battery will burn out the LED. So a resistor is used for providing required voltage and current.
Calculating the value of the resistor :-
The value of the resistor can be calculated by the ohm's law, which states that, the potential difference (V) across the conductor, is directly proportional to the current passing through the conductor.i. e.
V=IR;
where, R gives the resistor value.
Now, we will use this to calculate the value of the resistor. Arranging the formula for the resistor calculation for an LED is :-
R = (V supplied - V led)/Current of LED in A
where, R is the value of the resistor in ohm's,
V supplies is the supplies voltage,
V led is the LED voltage, that is consume for proper working.
In the above circuit, V supplied is 9V, V led is 1.8V ( its different according to LED ), Current of LED is a 20mA ( it also varies according to LEDs ), Calculating the value of resistor will give =
R = (9-1.8)×1000/20 = 360 ohm.
Above we had divided the current with 1000 to convert the current in A from mA.
So friends, above we had get the value of resistor = 360 ohm and thus value of resistor is generally not available. So find the nearest one value that is 390 ohm and use it in the circuit. If you are concern about the value of resistor, then, make the desired resistor by combing them. We will know about these in the upcoming tutorials. Remember always to supply only 86% of the required current for increasing the life of the LED. i.e. A LED with 30mA current should be supplied 26mA current.
Now, we had to calculate the power of the resistor, that we should use here. The power is calculated by multiplying the (V supplied - V led) with current of the led. Generally for a low current it is 1/4 watt, but it varies with higher value of current. It comes in many range as , 1/4 watt, 1/2 watt, 1 watt, 2 watt, 5 watt and so on. There is need for Calculating the power to supply the proper voltage and current, so that it glows with its full strength.
In the above circuit power use is =
P = 7.2 × 20/1000 = 0.144 W.
So here, we will use the 1/4 watt resistor i.e. 0.25 Watt resistor. Here we had to also use the power range that is nearest and higher than the required wattage, it not available.
So friends, for the above circuit, 390ohm/0.25 Watt resistor is required for the proper working of LED.
Series combination
V led = Sum of voltage of all LEDs. (1.8+1.8+1.8)V = 5.4V.
Current ( in Ampere ) = 20mA/1000 = 0.02 A.
V supplied = 9V.
R = (9-5.4)/0.02 = 180 ohm.
P = 3.6V × 0.02A = 0.072W.
So, the required resistor is of 180 ohm and of 1/4 Watt.
Parallel Combination
In the above circuit, first type of parallel combination is used, So, here we know about it. Another type of combination is described ar the end of this tutorial.
So, as we know the properties of a parallel combination, So,
V supplied = 9V,
V led= 1.8V ( Voltage is constant in the parallel combination ),
Current ( in A ) = sum of current of all the LEDs i.e. ( 20+20+20 )/1000 = 0.06A.
Now, R = (9 - 1.8)/0.06 = 120ohm, and
P = (9 - 1.8) × 0.06 = 0.432 Watt i.e. nearest to 1 Watt.
Hence, the resistor used is the 120 ohm/1 watt resistor.
In the second type of parallel combination, we had to add different resistor for all the LEDs according to its specifications. Hence, we can consider it as a combination of various simple circuits. The connection of it is shown above, which will clarify everything regarding this.
So friends, that's all for this tutorial. Hope u enjoyed it. If you have any question regarding this tutorial, then ask me in comment box.
Thanks
How to Electro ( Samridh Sharma )
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