Electronics 201: Pull-Up and Pull-Down Resistors
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- เผยแพร่เมื่อ 8 เม.ย. 2012
- In this Electronics 201 lecture, we talk about the useful tool that is the pull-up and pull-down resistor. We also go over the concept that is the tri-state buffer.
I'm looking for suggestions for future videos, so if you have any topics, just put them in the comments below.
As usual you can check out my blog at
8bitprojects.blogspot.com/ - วิทยาศาสตร์และเทคโนโลยี
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I've watched other's, yours explain everything, doesn't take many things for granted, it's complete and clear as well
Finally, a "complete" explanation which made sense, thank you
Im really happy how you talked about in detail the floating state in the beginning, a lot of other videos dont talk about that and why anyone would want a pull up or down resistor. Thank you for helping us!
Thanks! I had looked up the definition of pull up and pull down resistors several times without it making sense - now I see it was because I wasn't thinking about impedance.
Thanks for talking about impedence. Finally makes sence to me. I've tried to wrap my head around this for a while, never thinking of that the mcu has a resistance.
One of rare youtube videos I let commercials roll (muted).
hHD, your work is appreciated. thanks
key take aways 1. floating is bad 2. current is lazy , takes the path of least resistance 3. Impedance is your friend. thanks for the clear explanation
Thanks a million! I am kind of playing with basic electronics for three years and thanks to you now I really know what is going on inside.
Simply GREAT!
Thanks for the video friend, I really learned a lot about "philosophies in creating circuits" and electricity in general because of the ways you displayed this information! THANK YOU! it's rare to find such clear and concise conveyance of information on this subject
That was a great video! I learned a lot quickly. Greetings from Arizona.
Well done, very useful
Value R of Pull-Up
just wanted to point out that in the Pull-Up case, the value of the Pull-Up resistor has to limit the current flowing to the input pin and ground. it is preferred to be 10 times less than the impedance of the pin otherwise, a loading effect will be present as a result of the voltage divider, hence it is better to have the Pull up resistance Value R as 10 times less the impedance of input pin.
Good point, Ali H. Input impedance is desired to be high while output impedance is desired to be low.
This makes so much more sense now...Thanks for the tutorial!
Thanks heaps for the unique way of explaining the concept pull-up and pull-down resistors - it's the easiest to understand so far!
best explanation even in 2021
Pull-up and pull-down resistors well explained, thank you !
Excellent tutorial, thanks!
Floating = bad? That's not why my swimming instructor said...
What did he say?
dad's joke
Fantastic video - allowed me to explain the concepts better to my electronics club!
Thank you Great explanation. I thought I was the only one not able to understand the concept by the comments below
Thanks for this, the explanation and analogies were excellent! It really helped a lot!
Very clear. Champion tutorial mate. 10/10 would watch again.
Great tutorial, answered a lot of questions for me. Thanks!
Awesome video!!!! Thnx for the explanation were learning about this in automotive engine performance/diagnostics
Always was a source of confusion for me. Thanks for making it clear now.
Dude, amazing video, I have no idea about electronic circuits, but this helped me understands some of these Arduino demo projects i'm building. Thanks heaps mate.
Thanks for the video! Quick and clear explanation.
Finally, one video to answer all!! This is a GOOOOOOD VIDEO!!!
Thank you for this video, it thoroughly explained that logic is not on and off, but High and low. I had then misconception that it was High and off, but this video helped me realize that off can not be a logic state as there is an absence of info.
I thought Wikipedia's entry on this subject was concise and explained the concept really clearly, hope it helps someone:
"A pull-up resistor weakly "pulls" the voltage of the wire it is connected to towards its voltage source level when the other components on the line are inactive. When all other connections on the line are inactive, they are high-impedance and act like they are disconnected.
Since the other components act as though they are disconnected, the circuit acts as though it is disconnected, and the pull-up resistor brings the wire up to the high logic level.
When another component on the line goes active, it will override the high logic level set by the pull-up resistor.
The pull-up resistor ensures that the wire is at a defined logic level even if no active devices are connected to it.
A pull-down resistor works in the same way but is connected to ground. It holds the logic signal near zero volts when no other active device is connected."
As a beginner, I can tell that it's not explained well.
I need to read it a couple times, but that makes sense to me😎
Dude, very good instructional videos on electronics basics. I have watched three so far and plan to view more. Man, you should do many more of these on more electronics topics. How about one on H-Bridge motor controllers. Keep up the great work.
Thanks for this! I was having some trouble grasping what each type did but this seemed to help.
Now this is a more or less decent explanation, though not perfect. I had watched a few other videos on pull-up/down resistors and this is the first video I liked. Thanks. Now FINALLY it makes sense to me why and how it works.
Excellent tutorial. This subject was a always a bit fuzzy to me but not now!
Brilliant! You made me understand this. Many thanks
Excellent description, this is perhaps the least head-hurty description of why a pullup/dn resistor works, and more importantly, why a given value is chosen.
Excellent tutorial. Best explanation I could find.
Best video on the subject out there
Great video, man. Very informative, thanks a lot!
Thanks, cleared things up a little for me.
thanks for the explanation. It's very clear
Good tutorial!! Easy to understand. Great job！Thanks！
Great lecture. Made it crystal clear.
Amazing explanation!! Thankyou so much!!!
Excellent explained.
Great! Very good explanation of the idea
really your lecture helped me a lot in understanding that concept...thanks brother...
Thank you buddy....really saved me a lot of time.....thank you....
'current is lazy' :) good one.. easy to remember the concept.thanks
I think of a pull up or pull down resistor like a mechanical spring. Since the symbol for a resistor looks somewhat like a spring it is easy to remember. With a pull up resistor it is like a spring which tries to keep the voltage level at the level of the pull up source. Using a switch to ground "stretches" the spring down to Ground. Once the switch is released the "spring" returns the voltage to the higher voltage of the pull up source. With a pulldown resistor, the spring is trying to hold the voltage level down but can be stretched upward when the button is pushed.
Thank you so much for this video, i watched so many videos but they are all confusing except for yours. I just got started with the official arduino starter kit and i completed the project number 02 and also completed project 03 but i was still stuck at project 02 as to why there was a 10k resistor after the switch. I knew it was a pull down but a co worker today just confused the heck out of me and it turns out you confirmed i was right from the beginning. I'm so happy to learn my logic is healthy lol, there is nothing i hate more than thinking logically and be wrong and have no clue why. I can finally move on because of you. You're the best!!! And... I subscirbed to your channel, there seem to be a few good videos to watch laters, i just dont know how many but cant wait to find out.
Hi there, I think you meant to say that pull up resistor should be 1/10th or 10% of pin. In the case of pull up with V+ at 5V, 10kohm resistor vs 1kohm pin means that by simple voltage division, you actually have 0.45V at microcontroller pin which defeats the whole purpose.
Very good description!
201 = You Are The Best.
Even if it's kinda confusing cause of the used words, it's still a very good video and better than the other ones available for pull-up and pull-down resistors.
Thank you, very useful video
Nice tutorial, you're very clear, thank you !
Fantastic explanation - Great video. Thank you!
Woa I know pull up and down resistors.
Thanks for the great explanation!
Very educational video! I clearly understood pull up finally. You should do lectures on Polish school. Cheers!
Aspiring computer/mechanical engineer here - this was VERY helpful!
likewise brah. g/l for the both of us! ;]
great video, I love digital electronics, and this helped me solidify some things. And a side note; at 3:03 as well as the concept of pulling-out XD
This was helpful, thanks!
Hey m8. Thanks for my daily dose of education. :-)
Thank you! It was very clear :)
this helped me a lot, thank you!
7:45 why would any current gets pulled straight to ground when the resistance of the pull down resistor is larger than the mcu, isn't it suppose to go to the mcu instead because it has lower resistance ?
Nice lecture! Keep up the good work :)
Thank you for the nice tutorial...
very good teaching ...
Thanks a lot! Very helpful...
Great vid. How do you measure the input impedance?
good explanation mate. thanks
if i have a 10k resistor and say 40 inputs on a mega and do the pull down thing, will all that power going into the resistors be too much and will it heat up the resistor too?
Great stuff, man! Thanks. I need to translate this from your switch example to interfacing a microcontroller (output) to an LDO voltage regulator chip that has a handy extra pin to control on/off. I'll think on it a bit...
Pull up is active low - when button is "active" pin is low.
Pull down is active high - when button is "active" pin is high.
very nice explanation
so if i didnt know if a chip encorperates the pull up resistor for i2c and i put the resistor in, it wouldnt effect the i2c at all. so basically always put in a resistor and 5v supply for i2c?
This never made sense to me until now cheers
I FINALLY understood this
But in the case of pull'down resistor noise signal would also go to MCU (since it has lower impedance) instead of the ground?
On 7:38, lets say that µc has an impendance of 10Ω, which means that the resistor should have 100Ω, correct?
Why is the floating current choosing ground over the microcontroller when ground has a resistance of 100Ω and the microcontroller has a resistance of 10Ω?
He applied the one tenth value to the wrong resistor.... Your question is justified.
From another website: The general rule is to use a pull-up resistor that is an order of magnitude (1/10th) LESS than the input impedance of the input pin (10k-100k). An input pin on a microcontroller has an impedance that can vary from 100k-1MΩ
In case of pull down resistor. When the switch is open why the current would not choose the MC path because it has less resistor?
Thank you
+MrACG66 Yes, he explains that concept in reverse for the pull-up.
But when I drew that same circuit on proteus using a led instead for a micro controller, I still have to flip the switch before the led comes on and you said for pull up when it’s open it’s on
conceptually, would it be better to have a pull up resistor as this saves power in a microcontroller? instead of constantly letting it run to GND with a pull down.
Great video, the only thing i'm still confused is in the voltage that the microcontroller 'sees' (in the pull-up), i guess is less than 5 volts due to the resistor??
Well done!
hot!!
Nice tutorial.....does this apply to pull down resistor value for mosfets? you mentioned R= 10* impedence input.
Thanks for a great tutorial! There is something that i still do not understand, and i see others with the same query, however the responses seem to be addressing different issues:
In a PULL DOWN scenario, when the switch is OPEN, why wouldn't the 'stray voltage' still choose to go to the path of least resistance to the micro controller [with the lower built in resistor], than go straight to ground [with the higher pull down resistor], which was the whole point - to stop the stray voltage entering the pin...
i have no idea either. Did you ever figure this out?
Who the fuck would dislike this. This is better than Kahn ac..
what is the difference between pull up signal or pull down signal control? which is controlling?
Nice lecture
On the pull down, with the switch open, why is there any current flow at all from the ground?
Something I don't understand... When you close the switch in a pull up resistor circuit like the one in the video, the 5v connects directly to the ground, with only the resistor in-between. Would this not fry the resistor?
Can anyone explain to me again why the Impedance in the micro-controller is our friend? How does it work when we have a lot of current and when we have a weak signal? Do we still benefit from keeping one resistor (impedance) or do we have to change the resistor (impedance) to get good results in those 2 scenarios? thank you!
Hi-
Using the Amtel 1284P. Trying to send a signal to the CLEAR pin on a MAX16054 for the purpose of auto-shutdown via software.
The setup is like the first example in the MAX16054 datasheet. Need to calculate the value of the pull-down on the CLEAR line.
Tried to include links to the datasheets, but TH-cam wouldn't let me. Sorry
Thanks!
Excellent video. I would just like to point out that while floating pins on _inputs_ are generally considered bad, a floating pin on an _output_ is either doesn't matter, or is required like with multiple outputs on a buss configuration. The floating output would (obviously) be a separate video, but it should be stressed on this video that the "bad" label is applicable here only because this video is dealing with inputs.
I heard Pull-up concept is also used to increase the voltage level of the sensor when sensor gives comparably lower values. How does this pull up resistor used in that application ?
In the floating state, for there to be a "stray signal on the pin" that means that the micro controller also has a ground in addition to the main ground. The stray electrical signal would flow to micro controller's ground. Is that a true statement? If not why?
When you say the pull up circuit is built in to most uC's, does that include the Arduino? If so, does that eliminate the need for this and allow you to just wire 5v to button to pin?
What microcontroller are you using?
Excellent!!