# Beginner Electronics - Beginner Electronics – 7 – How Much Resistance?

## Beginner Electronics

29 Lessons

### Beginner Electronics – 7 – How Much Resistance?

what's going on everyone my name is Kota moore and welcome back to electronics episode 7 in this episode we are going to learn how to choose the proper value

of resistor to put into a circuit now in our case we just learned about LEDs so we need to know what resistor value how much resistance we need to put into a circuit so that

our LED will work and not burn out now there's a really cool equation for doing this for any electronic component that you need to figure out if you need a resistor for but you need to know some

information first first you need to know what component are you trying to get the resistance value for and I'll explain all this in a little bit don't worry then you need to know the voltage I'm

just going to put V you need to know the voltage of your power source I'll just abbreviate it like that then you must know the forward voltage the forward voltage of whatever component you have

and then you must also find out how many amps your component uses as well now this all looks crazy but don't worry we know love this first of all what is our component well in our case we want to

figure out how much resistance value we need for an LED the LED is our electronic component like I said this equation will work for any electronic component that you need to figure out if

you need resistor for okay so an LED is our component next we need the voltage of our power source in my case I am going to be using a 9-volt battery if you have a battery holder for say two

double-a batteries that's going to be I believe three volts you just add up the voltages on the battery but I'm just going to be using a 9-volt battery all right now what in the world is forward

voltage of our component well in order to figure this out you need to know the manufacturer of the component that you have so who created your component if you know that you can go online look up

the manufacturer of your LED or of your electronic component and they should have a datasheet online that shows you what the forward voltage would be in my case when I ordered my LEDs it came with

a little note card that told me the forward voltages of every single LED that I ordered so for my LEDs the forward voltage for almost all of them is 3.2 volts that's

basically how many volts the LED will use up if you don't know this that's fine just start off by using a 1.5 kilo ohm resistor and that should be plenty to not burn out your LED but it is

important that when you order electronics components know who created them so you can look it up online or save any of the cards that they send you that gives you information about the

product so the forward voltage you can really get by just looking up who created your LED or your component and next we also have to have the amps that our component uses up this is also found

in the same way by looking up the manufacturer and the datasheet of your component in my case it the LEDs that I have take up 24 milliamp so I'm just going to put em a now because this

equation only works with amps we have to convert milliamps to amps 24 milliamps is basically 0.02 for amps and I'm assuming that you can figure that out I just took my 24 milliamps and multiplied

it by point zero zero one and that'll get you amps now we have all of the information we need for this equation to tell us how much we how much resistance we need basically what we are going to

do is we are going to say the amount of resistance we need in this circuit is going to be equivalent to and I'll write it out first we have our power source voltage minus the forward voltage of our

component all divided by the amount of amps we have so if we actually plug in numbers for this we're going to say resistance is equivalent to if we look at our power source voltage I'm going to

be using a nine volt battery so it's going to be nine volts so nine minus the forward voltage of our component which my LED is take up three point two volts so three point two divided by the amount

of amps our component takes in our case point zero two four amps so I'm just going to write point zero two four so if we simplify this R equals nine minus 3.2 is I believe five point

so we have to do 5.8 / 0.024 and if we whip out a calculator this is equivalent to approximately rounding all the decimal points 240 ohms there we go we know if we want to use my specific led

in a circuit where the power source or the battery is a 9-volt battery we must have a 240 ohm resistor in the circuit or somewhere around there it doesn't have to be exact to operate my LED at

its maximum potential according to the manufacturer so it seems like quite a bit of work but eventually you'll begin to memorize this equation just write it down somewhere you are going to be using

it a fair amount if you ever questioned how much resistance you need for a circuit we look up all this information plug it into the equation and you'll get the approximate resistor value now

resistors don't come in every single value so you are going to have to approximate say I don't have a 240 ohm resistor say I have only I don't know a 280 ohm resistor that'll be plenty I

mean it's even more than the recommended resistance value even if I have to go a bit less than 240 that's completely fine my LED will still work and probably not burn out if I don't go too far under now

if I only have a 100 ohm resistor that might be a problem but I hope that all made sense as long as you know what component you are trying to get the resistor value for in our case an LED

you can look up all the other information online your forward voltage in your amps and obviously you know the power source because you're the one providing it the battery and then you

can use this equation I hope this all made sense everyone if you have any questions whatsoever let me know down below in the comments and either I or someone else will hopefully answer your

question and/or help out with any of your problems again thanks for watching everyone and I'll see you guys in the next video

We figure out how to calculate how much resistance a circuit needs!

See my website: https://codenmore.github.io/