In today's video we will learn to calculate the resistance to the LED, let's see what the ideal resistance to connect a LED without that we will harm or degrade.
Come to the video.
To learn how to calculate this resistance we must consider three values: What power we going to feed? In this case we will do with 5 volts.
Those 5 volts are going to get from a charger a cell phone that you no longer use, which normally bring that voltage and we will connect a LED.
In this case I will connect a white LED.
We know it What is the ideal voltage work? and what is your current consumption? If we see in the table, Each LED has a voltage dream job.
in this case for example red They are between 1.
8 volts and 2.
5 volts, yellow equal, green are between 3.
4 volts blue 3 to 3.
4 like whites.
And the current dream job almost all LED it appears there is 20 milliamperes.
So knowing what we will work source which it is 5 volts, We will place at this time an LED white It is working ideally between 3 and 3.
4 volts and consumes 20 milliamps.
Let's do the math.
We know then that this LED we will use 3 volts and 20 milliamps.
If we had a 3-volt source We would not need to place a resistor.
Let's see the example.
This battery, if you get to see there this battery is 3 volts.
ie if I connect the LED I will turn without any problems no need using resistance What other according to the table I work with 3 volts? The green.
Please note that this has polarity LEDs have the same polarity, The longest leg is positive going, short to negative Battery, here we see the positive above and this part that says nothing is negative.
So long leg goes to the positive and negative.
Hence we see on As we will not use a battery exact 3 volt but a source of 5 volts we calculate the resistance.
We use Ohm's Law What Ohm's Law says? The intensity or current It is equal to the voltage on resistance.
As we will find resistance we should clear it, ie dividing resistance is passes multiply and multiplying the current is would split.
We would that resistance It will be equal to the voltage on the current.
What is the voltage? The voltage is not the 3-volt LED nor 5 It turns out that we need to find the voltage falling on the resistance, the voltage is here Is the difference between total supply voltage least we are using the LED Because this voltage is consuming this LED, ie it would be five least 3.
To understand the formula would voltage source less voltage LED on the current circulating want by the circuit, and what will it be? the LED.
We continue here Source voltage which is 5 lower voltage LED, which is 3 It is equal to 2 on the LED current How much is the LED current? 20 milliamps.
As we need to stop expressed in amperes when Milis 10 is the least 3 That is the point we have to take 3 places to the left.
One, two, put a zero .
tres 20 milliamps equals 0.
When doing this It gives us 100 Ohnmios This is the resistance value that we will use.
Here I have my 100 ohm resistor The color code when it has four bands is brown, black, brown, gold But if this resistance is not commercial, often happens, for example we have given 110, 120 which they are resistors that are not commercial we find the closest up not down because we would be increased the current and the LED may be damaged or degraded.
So we must seek it up; for example if we would have given 110 or 120 are values that are not commercial, ie you are going to an electronics store and not going to get.
I think the commercial value there above 110 and 120 I think it is 180 Ohms, or the commercial value they get more close to this above.
You'll see that if you use a 330 ohm resistor or close to 500 ohms, you just going to work only the LED he will not illuminate with enough intensity.
Many times in this way we want the circuit: not enlighten us much.
This would be the ideal, but above these also we will work.
Let's ride the circuit.
This is the power I got, It is an old cell, It is 5 volts and gives to 550 milliamperes enough to light several LED.
And what I did was open the two terminals, I cut, Some people have asked me in other videos what if you are first or first resistance is the LED? Do not care, as is a series circuit resistance acts similarly: before, as in this case, or later.
It will not be any difference resistance is going to limit current in either points since the current has no other way.
So I am going to place.
I'll just add it to the test Then I'll put welding.
We connect our 5-volt power source.
We connect you It does not work we because remember that the LED has polarization.
The longest leg will go to the positive so I'm investing, crossed wires and connect again.
That is our LED illuminating us.
Let's make a temporary connection.
Then this must be left well done, welded and leave well insulated.
There is already our circuit The power supply are these two black wires It passes through a 100 ohm resistor It reaches the longest leg of the LED which it is positive and negative with the negative circuit.
I will Bajgar some lights to realize enlightening with sufficient intensity.
Like we saw the other option which is connected directly to 3 volts.
This video was made especially for my friend the Fefa channel M which makes stunning homes for miniature dolls.
If you have daughters or nieces Be sure to go through the channel Fefa M.
He does amazing things and he asked me the favor to teach him to do this because I think you will use to illuminate the kitchen, for lamps within the amazing things he does.
Visit the channel dollhouse Fefa M.
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