# Voltage divider tutorial

This tutorial is about voltage dividers. A voltage divider circuit uses resistors

to reduce voltage. You can use voltage dividers to do a

lot of things, like create a volume control circuit or generate

reference voltages and much more. If you apply Ohm’s law you’ll find that

one volt spread across two equal value resistors gives you

half a volt in the middle. So you are getting half the voltage. And as you would expect, four equal value resistors would give

you 1/4 volt, 2/4 volt, and 3/4 of a volt. For the sake of simplicity, let’s

just use two resistors. If you use two resistors of different

values, the voltage gets divided up in proportion to the amount of resistance

there is. In this example with twenty percent of

resistance on the bottom, you get twenty percent of the

input voltage on the output. If swap the position of these resistors, now with eighty percent of the

resistance on the bottom, you get eighty percent of the input voltage

on the output. By the way, voltage dividers will work

fine with both AC and DC input voltages. And this is the equation you should use

to calculate the output voltage voltage depending on the resistors

you are using. And if you are not getting the output

voltage that you want, try the equation with some different resistor

values, or rearrange the equation. Alright, here are some more examples. Here I am taking ten volts and dividing

it down to one volt. Here I’m taking five volts and dividing

it down to four volts. And here I am taking 100 volts and dividing

it down to one volt. You might have noticed I’m using extremely different resistance values

here… sometimes a few ohms… sometimes a few megaohms… but it is

ultimately the ratio of resistance values that determines the output voltage. Now that does not mean that when you

build a real world voltage divider you should use low value resistors. Whenever you create a voltage divider you

have to be aware of the overall power consumption of the circuit. And you calculate it using this equation. With this circuit, the resistors are

dissipating 0.1 Watts which is very little so everything is fine. But in this circuit the resistors are

dissipating a thousand watts! So the resistors are going to catch fire! The output voltage the same in both cases, but the power consumption is totally

different. Also before you create the voltage divider,

you have to be aware of how much current your voltage divider has to supply… because voltage dividers are not the same

thing as regulated power supplies. There is going to be a voltage drop

as soon as you connect your device to

the voltage divider, depending on how much load there is. For example, here is an unloaded voltage

divider giving me five volts. When I connect a microcontroller that draws

just one milliamp, the voltage drops to 4.56 volts. And that’s not so bad… the microcontroller

will still work… But if I try to power this motor that would

normally draw 100 milliamps from 5 volts, the voltage drops down to 0.5 volts,

and the motor won’t work. So this voltage divider would be a terrible

power supply for motor. In general, you shouldn’t be

using a voltage divider if you have to supply more than ten milliamps. But if you

want to screw around with resistor values and see what you can get away

with, you can calculate the Thevenin equivalent resistance of the voltage

divider using this equation. And yes it also happens to be the

same as the parallel resistance equation. Once you have calculated the Thevenin

equivalent circuit, you can calculate how much voltage your

load is really going to receive using the voltage divider equation from earlier. Now what are some real-world circuits where

you could use a voltage divider? Well an easy one is a volume control

circuit that you could use before an amplifier. And all you are doing here is just

dividing voltage with a potentiometer. In this amplifier circuit, I’m using the

voltage divider to add a DC bias to an audio signal so that the transistor can

turn on and amplify the signal properly. And finally the most obvious use of all is

powering devices that expect a certain voltage and only draw tiny

amounts current, like a cheap calculator or something. And you should really be using a voltage

regulator to do this, but what can I say some people are cheap. Alright I’m done with voltage dividers and

thank you for watching!

Awesome!! Thank you!! WOWWW

very good video and informative as well.

Nice video 🙂

Brilliant thank you

good tutorial for anyone looking for a quick review

a true hero my friend perfect

Buen dia, soy ingeniero electrónico y me encantan sus videos… son la locura! Hacia tiempo que no veia sus videos… en Colombia también hay necesidad de aprender y sus videos estan bien explicados. Saludos y espero su prox video. Have a nice day !

Thanks for the tutorial, very informative.

Another possible use (I hope it works, I still have to try it) is to regulate the Output voltage of a sensor which works on 10V basis and gives you 0-10V Output down to something a 5V basis microcontroller can handle in it's analog inputs (so regulate 0-10V signal down to 0-5V signal to be able to read it).

Question, you say it's bad to run a motor off of a voltage divider. What about a blower motor in a car, it runs off of the blower motor resistor which is 3 resistors in series and the fastest speed bypasses them. That's a voltage divider, right?

what if we remove GND in Volume control circuit (min 3:21) ???????????

lol "This box looks exactly like a calculator."

so i can use this to charge "dead" lithium batteries with really low currents?

Awesome video. I didn't fully understand how it works until I saw this.

this is what i was looking for, that combines several parameters ( electromotive field force to current and power calculation )

Finally i understood…

Thank you it was so helpful!

Thank you so much for explaining this in an understandable way.

KNOWLEDGE!

Can you use them to turn a transistor on and off? let's say the upper resistor is a thermistor and a normal resistor on the bottom and a transistors base terminal on the center. Will this turn the transistor on and off depending on the temperature?

Fundimetal question: Why does the voltage drop over a resistor?

Hello, great video!

The amplifier circuit near the end of the video,

it will only give a 5V or zero, right?

I've never heard the term "thevenin". Definitions, anyone?

Either you talk too fast or I think too slow…probably the latter. Great video! Thanks I understand it better now, I just had to hit the rewind button a few times. lol

Thank you so much

whyyyyyy is this soooo much easier to understand than my textbook

This is what i don't understand: I've looked up for an analogy about circuit behaviour with resistors, and this was it: A circuit is like a bicicle wheel ( while the bicicle is turned upside down ). The constantly moving wheel represents the circuit, and if you touch the wheel with your hand ( a resistor ) then the WHOLE part of the wheel will loose speed (voltage) ( The same applies with circuits ). But then i came across with these voltage dividers and doesn't make sense how i can obtain a fraction of voltage! ( If we put 2 hands ( resistors ) in the bicicle it would loose even more speed but still the speed is the same in all parts of the wheel / circuit. Can someone explain this to me?

How to get desired voltage output. I figured it out.

I've chosen 12Vdc as my power supply. I've chosen 5vdc as my desired voltage output. I've chosen 15,000Ω as the total resistance.

My equation for how to get desired voltage output.

R1 = (Vout / Vin) * Total Resistance

R2 = Total Resistance – R1

R1 = (5Vdc / 12Vdc) = 0.0.41666666666666666666666666666667 * 15,000Ω = 6,250Ω

R2 = 15,000Ω – 6250 = 8,750Ω

R1 = 6,250Ω

R2 = 8750Ω

Using equation : Vout = Vin * R1 / (Total Resistance)

5Vdc = 12Vdc * 6,250Ω = 75,000Ω / 15,000Ω = 5Vdc

Presto !!! Almost too easy.

With the motor demonstration, you have an R1: 800Ω, R2: 1kΩ resistor, with a load of 50Ω.

Now I'm not too familar with how the voltage is dropped down, but I'll give it a shot, and try to solve the problem of the voltage dropping.

What if instead of R1's value being 800Ω, you make it a 40Ω resistor. Of course the 40Ω resistor would have to be rated for more than 2 watts.. right?

With that, then the R1 : 40Ω would supply 0.225 Amps, at 5vdc.

How or where could I learn a little more about how to calculate that? To account for the voltage drop when you hook up a load with a specific resistance. Or is it just as simple as the fact that it's just another resistance in the circuit, or another resistance in the voltage divider circuit? Am I right? If not, could you please point me in the direction to where I could learn a little more about how to solve that problem?

Can someone help me please? 🙂 I have 12 VDC psu and I want it to power a circuit(12V 40 mA under load), but also a DC motor. the motor works fine with 6 V and it draws about 90 mA. I have messed around with resistors and tried to devide the 12V psu to 6V, by using 100 ohm resistors. Is it "safe" to do that?. cant seem to find an answer anywhere else 🙁

Thanks a lot for this video.

Thank you!

Great channel, great knowledge, too helpful. Thank you for the equations.

This made voltage dividers make sense to me finally.

I guess I am cheap, lol. I was preparing a question just about what kind of load can I apply to such a circuit. What if it is always a high impedance load? I don`t see the problem in the case the load draws less current than V / ( R_1 + R_2 ), which is flowing through the divider anyway. The curent flowing through the load would alter the voltage, but this could be computed if the load current demands where known beforehand.

Am I correct to conclude that the issue is going to be when the current drawn by the load is highy variable? In this case it is not possible to design a divider that will give the correct electrical tension.

Your formula V²/R doesn´t apply here as you have a series circuit.

The more I get into electricity, the more questions I have

So I tryed to calculate that example about current supply at around 2:10. How do you calculate the voltage drop? What does it mean for the current if you say the Microcontroller draws 1mA? To calculate the new voltage do you subtract this 1mA from the 5mA you had before? So 4mA*(resistance of the parallel path)?

A wonderfully clear and concise tutorial. Brilliant video, like the rest of your work. Appreciate your time and learned a lot👍

Concise, clear and rich in content! Awesome!

@3:35–3:43 Can you do a video about combining circuits to create more complex circuits? In particular, I'd like to have the topic of creating "modular circuit" addressed where you'd show us how to (or examples of) circuit blocks that don't affect adjacently connected circuits.

I'm making a hybrid drive system with a used inverter generator hooked up two a AC 3 phase to dc rectifier and a dc motor , when I run it I'm getting DC voltage up in the triple digits. What can I do to reduce the voltage to at least 24 volts but be able to get a decent amount of amps 50 at least.

Can anyone explain why If i have 700v AC and use 2 Equal Value 4M OHM Resistors, it doesn't give Half Voltage (350v), it gives 296v? (Which is 700/2.36 instead of 700/2) I checked the Tolerance of the Resistors, and they are both 3.91M Ohms Exactly

For more information, Im using the voltage divider to Lower the voltage from 700v to anything below 500v for a tester i have. so the current should be little to none.

Most clear explanation!!

What is the advantage of using zener diode instead of this voltage divider?

what happens to ic when vcc is loe

Now I fully understood

There was always somewhat of a contradiction about electricity, in my head at least. Electricity takes the path of least resistance is what im always and what I remember from my school education and generally all around. Why do for example led's soldered in parallel onto a positive and ground wire all light up? There must be something wrong about that first statement. Somebody care to explain please 🙂

I feel so dumb when I look up videos about electronics lol.

Thank you, it was very informative

the real question is where's the catmercial break?

💚💛💜💓💕💖💗💘💝💞💟👍👍👍👍

PERFECT… THANK YOU

I have a question I want to make voltage divider for 12 V 🔋 with four 1000 ohm (1kohm) resistors. I want to reduce voltage that my Arduino can calculate the voltage. Is this value is good. For the normal resistors? Please help me.

Anyone want to listen this: 3:48….Some people are really cheap xDDDDDDDDDDDDDDDDDDD!!

my voltage divider works as load and got burned what to do please reply

I want to go from USB to 1.5 v DC. Where do you get a converter for that?

…..So I won't be "Cheap"

A damn fine tutorial!

Thank God you make this video…. 🙄🙄🙄Thank you so much

Hi Need your help ..

I have a celling fan (75 watts & 300 RPM Elctric volts 220) normally I like very slow speed but my fan runs very fast on 1 speed regulator .. I need to reduce its speed but can not be done thru regulator as it is alreayd 1 ..I thought to use Resitor and fix it in Regulator on positive wire .. Can u suggest me following .

1. will this work using resistor to slow the speed of the fan ?

2. Is it safe for the fan .?

3. Second what capacity of Resistor to be used to find the result ..?

Kindly repond to it thanks

so this would not work with a 2 amp draw am i correct

Thank you, exactly what I was looking for!

Does a voltage divider limit current too?

What material i need 70amps and 5000wats maximum,, 220volts ac

Can I use (+) and (-) of a AA size rechargeable battery in the top resistance and bottom resistance (following your circuit) ?

Finally, some real world examples, not just theory and formulas as in many other tutorials

i believ on it the actual measurement and computation should meet and the requierment… nice..

Do you have a tutorial on how to divide voltage for more then 10mA ?

Like how do i divide 15.1v 0.4A into 12v 0.2A ?

I sum electronics as the flow and control of water in a network of pipes with resistance and gates.

I'd say the most popular IC that uses voltage dividing is the 555 timer.

Image is too small

I kinda wished you had added one more example that shows what happens when you try to divide a mere 5 volts with the 1 and 9 ohm resistors. Many of us juniors use 1/4 watt resistors, and if my calculations are correct then 5*5/1+9 = 2.5 watts, which should burn up a 1/4 watt resistors (albeit not as badly as your example). Correct?

Resistor is current divider not Volt . Nicely explaination

شكرا على هاذا الترجمه

Is there any good books to read about voltage dividers.

Relatively new to electronics. Got lost @ 2:39.

However, I've fount that watching a tutorial several times, along with wathing others, it sometimes sinks in and I get the concept. Cheers

Can u plz mak a video of voltage divider for a arduino uno or mega with input of 12V…. plz reply

Hi, plase turkish subtitle

Shakespear

On top of that, if you can, you could add an op-amp follower to make sure the voltage at that point doesn't change no matter what you want to attach. Still won't solve the current problem.

Let's say I have 27volts and I want to get an out put of 1ma, what kinda resister would I use???..

I'm kind of new at this but I'm curious what if I need a constant 12 volt but I need 7.5 amps to go down to 5 amps what do I do. Like do I just take a 7.5 amp fuse and then wire to a 5 amp fuse or would it blow the 5 amp fuse…

If you have a 20 amp draw Frome a battery at 12 volts but you want 2.8v at 20a, What is the most efficient way to achieve that? Note this is not just an example I'm going to use this in real life if there is a reasonable way to do this.

YES! HE SPEAKS ENGLISH!

Okay, you make electronics waaaaay more interesting than at school where we learned basically everything in theory. Keep it up!

(Know that this is now a 9 and a half year old video but its still very much informative and the quality is even competing to today's standards which is really impressive)

@ 1:22min

100V / (1+99Ohm) = 1A

1A * 99V = 99 Watt!

😉