Potentiometer Explained: How It Works and How to Use It

sponsored by PCB way this is a potentiometer it's an adjustable resistor they come in many shapes and

sizes we can insert them into test boards connect wires to them solder directly to them or solder them onto

circuit boards they usually have a dial a slider or an adjustable screw head which lets us change the resistance of

the component they are represented with symbols like these in engineering drawings we can use them to manually

adjust adust the voltage or current in a circuit when used to adjust current we call them a riat I'll explain how to use

both of these later on in the video see this game controller well the joystick has two potentiometers one measures the

up and down movements and the other measures the left and right movements this is a servo motor we use them in

robotics inside we find a small potentiometer which is used to check and control the position of the arm this

radi videoo uses a potentiometer to control the volume this DC power supply uses a potentiometer to control the

supply voltage this audio equipment uses a slide potentiometer so where have you seen them used let me know in the

comment section down below okay so how do they work if we look at a typical rotary potentiometer we notice there is

a metal protective casing on the back which is simply held in position by the small arms on the front

all of the parts connect onto a small brown sheet of insulation along the top Edge we usually find some letters and

numbers I'll explain these in just a moment we then notice a long shaft rising up off of the device we can

rotate this to alter the resistance of the component you'll see there is a slot cut into the top for a screwdriver or on

the side are some ridges which just help us grip the shaft we can also attach a knob onto this at the base of the shaft

there is a threaded section which we can use to attach the component to a sheet of material along the lower Edge are

three metal terminals we connect our circuit to these terminals these terminals can be straight or angled

depending on the application when we remove the back case we can see there is a track which runs between the two end

terminals another track runs in a loop at the center and connects only to the center terminal the outer track has a

very dark material over it this is a resistive material the track even looks like the symbol for resistance so it's

very easy to remember a wiper forms a bridge between the outer and inner track it is slightly spring-loaded to ensure a

good connection this is attached to the shaft rotating the shaft rotates the wiper the further we rotate the wiper

the further electrons will have to flow to get to the center pin and so the resistance increases we can also reverse

the connections so that we reduce the resistance as the shaft rotates on the printed text we usually find a k or M at

the end meaning thousand or million this one shows 1K meaning it's 1,000 ohms this one shows 500 K which is 500,000

ohms and this one shows 1 M which is 1 million ohms these values tell us the maximum resistance of this component the

first letter indicates the type B is very common it means the resistance changes in a linear pattern then we have

type A which gives us a logarithmic pattern we also have type c which gives us an inverse or reverse logarithmic

pattern however the letters used can vary by country and also by manufacturer so always check the manufacturer's data

sheets or you can check the performance with a multimeter by the way this is the new smart multimeter from KY weats and

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for you in the video description by using the resistance function on our multimeter we can see this 1,000 ohm

potentiometer has approximately 1,000 ohms of resistance across the entire resistive track we can connect between

terminals 1 and three to measure that or we can measure this directly across the internal resistive material notice the

resistance reduces as we move the probe we can plot this and notice that at about halfway we have half of the total

resistance this is therefore a linear B type potentiometer this one also has 1,000 ohms across the two end terminals

but notice the resistance changes logarithmically along the entire track this one is also 1,000 ohms but it

changes reverse logarithmically along the entire track logarithmic is is often used for volume control as it matches

the human ear linear is used for things like lights or signal control I've used the linear versions here to control the

colors of this RGB LED I'll explain how it works later on in the video but you can download my PCB project files for

free using the link in the video description you can then order the circuit board from PCB way our sponsor

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can design and build anything do check them out links down below we can get these dual versions which are basically

just two potentiometers joined together both are controlled from the same shaft these are useful in two channel stereo

audio volume control be careful though these have a low power rating these can typically be adjusted 10,000 times or

more they won't fully rotate usually just around 270° you can buy them individually or in

assorted kits depending on your needs there are multi-term potentiometers they also come in different sizes and usually

have a threaded section for mounting they have a long shaft which the control knob fits onto this is a 10 turn version

meaning the shaft can rotate 10 times this gives us very precise control of resistance it can usually handle

slightly more power too and this one can handle at least 1 million adjustments you'll notice that the body is much

longer than a regular rotary potentiometer that's because inside is a spiral wire track which provides the

fixed resistance this connects to the top and middle terminals at the center connected to the shaft is a slider which

can freely move up and down along a conductive track this is electrically insulated from the shaft the conductive

track connects to a circular terminal at the base allowing the shaft to rotate the flexible connector ensures a firm

connection the slider rotates with the shaft the plastic slider has some ridges which fit over the resistive coil when

the shaft rotates The Ridges will therefore follow the curve of the wire and so it can move up and down as the

shaft rotates a small spring arm sticks out from the slider and rubs against the wire coil this also rubs against the

conductive track providing a path for the electrons and allowing us to use just part of the total resistance this

one has a wiring diagram on the case showing the fixed resistance is between the center and right pin the wiper is

connected to the left pin on the back it also shows this component's maximum resistance of 5,000 ohms slide

potentiometers look something like this we Slide the dial to adjust the resistance they often have a flexible

cover for dust protection inside we have a resistive track and a conductive track the wiper acts like a bridge between the

two tracks moving the dial moves the bridge and changes the resistance the three pins are sometimes numbered

underneath but not always we also have six pin versions which have two sets of tracks inside these are basically just

two slide potentiometers joined together there are usually some other pins and these are just used for mounting the

device you can check the data sheet for the pinout diagrams or just use a Multimeter printed on the bottom are

some numbers and letters the first letter tells us the type of taper the numbers tell us the maximum resistance

this one shows 103 meaning 10 with three zeros after it which is 10,000 ohms this one shows 100K which means it's 100,000

ohms they do usually have a low power rating and are typically rated for at least 10,000 adjustments trimmer

potentiometers look something like this and they use these symbols these are much smaller and only designed for

calibrations of circuits with very occasional adjustments but the center is a rotating part with a small screw slot

or maybe a knob with an arrow these versions have less than one full rotation of movement so they aren't as

precise as the multi-term versions I'll explain these also in just the moment these components do have a very low

power rating so be careful they will easily break and they are designed only for occasional adjustments inside we

have a resistive Track Running between the two end terminals a circular conductive plate connects to the center

terminal and a tiny wiper Bridges across the two tracks and this is held in place by the rotor with this exposed version

we can see that the resistive track runs between the two end Terminals and the wiper arm connects to this and rubs

along it as we rotate it this then connects down through the center pin onto the middle terminal sometimes they

have a small wiring diagram printed on them but the unaligned PIN is generally the wiper pin it is easy to test with a

multimeter these small versions have a three-digit number printed onto them the first two are significant numbers and

the third tells us how many zeros to add for example this shows one1 meaning it's 10 with one zero after that so it's a

100 ohm resistor and that is the maximum resistance of this particular component this one shows 204 so it is 200,000 ohms

multi-turn trimmer potentiometers look like this they usually have a small metal screw which is used to adjust the

resistance very precisely the screw can rotate many many times these vertical versions have a resistive track between

the two end pins with a circular conductor in the middle and this connects to the center pin a wiper

Bridges between the two and connects to a plastic disc with gear teeth along its Outer Edge the thread of the cylinder on

the screw connects onto this adjusting the screw slowly rotates the disc and also the wiper precisely changing the

resistance so this gives us far more Precision compared to the single term versions this one has a small pin

diagram pressed into the case on the top of this one we find the numbers one2 meaning 10 with two zeros after that

which is therefore a 1,000 ohm maximum resistance version these long horizontal versions have a screw on the side this

one also has has a wiring diagram on the case so that we know which pin is which inside we find a resistive track and a

conductive track held onto a ceramic base the wiper Bridges across the two and is held by a slider adjusting the

screw rotates the thread and that moves the slider and wiper forwards or backwards along the tracks changing the

resistance very precisely the resistance is indicated with this number here it indicates a maximum of 1,000 ohms

resistance distance with all potentiometers make sure to check the manufacturer's data sheet for the

connection diagrams the rated power the voltage the number of uses and the type of taper many components will have a

parts number printed on them so you can search online and find the data sheet you can also get an engineering mindset

mug to help support the channel links down below for that we use potentiometers as voltage dividers or

current limiters with a voltage divider we connect the power supply across the two end pins and the wiper connects to

the center pin this pin provides our output voltage if we connect our multimeter to this output and to ground

we can see the output voltage varies as we rotate the shaft if we use the resistance function and connect between

the two outer pins the resistance remains constant we are measuring the total resistance of the track but if we

connect from the left pin and then the center pin we can see the resistance varies so we can use just part of this

total resistance here the battery is providing 9 volts on the positive wire and the negative wire is 0 volts so when

we connect them across the end pins the voltage needs to drop from 9 to0 across this length we can make that distance

long or short the same voltage drop will still occur just at a different rate let's say this track has 900 ohms of to

total resistance we could divide that track into nine segments 100 ohms each the electrons will all flow through this

track from one end to the other so the current is going to be the same at any point along the track so to find the

voltage at any point we just calculate the voltage drop we are starting with 9 volts Segment 1 has 100 ohms of

resistance so the current multiplied by the resistance gives us 1 volt and that means we have 8 vol Vol remaining at

this point segment two is also 100 ohms so it too causes a loss of 1 volt but it was only receiving 8 volts and so here

we have only 7 volts remaining and that continues along until we reach the end with zero volts remaining so now we know

the voltage drop at any point if we now take our wiper arm and connect to the track this lets us move along and make

use of the exact volt voltage we require because we are only using part of the total resistance and so we're only using

part of the total voltage drop this is great for signal and control applications but it is not good for a

power supply because as soon as we connect a load to the output the resistance of the load creates a

parallel path for the current and so the voltage will reduce we can also use potentiometers for current control but

we call this a Rio stat potentiometers only have a small power rating so larger current circuits will require a purpose

made riat which will look something like this they are generally much larger and can handle much more power we just

connect the power supply between one of the end pins and the center pin the electrons will flow from the battery

along the track and then out through the center pin as this is the only exit available moving the wiper changes how

far the electrons will need to flow to reach that exit the voltage drop occurs over this distance the further the

distance the more resistance the electrons encounter which reduces the current if we had a 900 ohm track we

could divide it into nine segments we connect the positive 9vt to one end with the zvt ground on the wiper all the

electrons need to flow through to the wiper the voltage drop Remains the Same between these two points no matter where

we move it at segment one one we are only using a small part of the total resistance so the current will be really

high at segment two the resistance has now doubled and so the current or half the current continues to reduce the

further we move along the resistive track until we reach the end where the minimum current can flow be careful

though if you move the wiper to the very start there is little to no resistance and so the battery will try to fully

discharge resulting in a huge current flowing here we can use this circuit to control the brightness of an LED just

connect the led to a resistor of around 350 to 400 ohms and then connect this to the potentiometer and use a 9volt

battery it should look something like this when we turn the shaft we can control the current and that changes the

brightness of the LED we need this resistor to set the maximum current for the circuit and that's just in case we

move the wiper too far otherwise a huge current will flow and it will just destroy the LED RGB LEDs are just three

separate LEDs combined into one a red green and a blue LED so if we control the brightness of each LED we can create

any color we want you can download my PCB file for free and order this yourself to make it home the circuit is

really quite simple I just use these value components and I'll leave the parts list in the video description for

you check out one of these videos to continue learning about Electronics engineering and I'll catch you there for

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