Computer Inputs: Pull-Up and Pull-Down Circuits

[@andrewk778]

While watching this video, I thought about you, investing equipment and time, all to share your knowledge and experience. NONE of this was available when I was a kid. Thank you for sharing.

[@Okie-Tom]

You are very good at teaching the very basic understanding of the circuits! Thank you!

[@sourikishona]

I don't know in which words I should thank you for this great video...❤❤❤❤

[@J.T672]

Hi Justin, I work for toyota a dealer and these videos are really helpful under standard circuit design . I've also been on various training courses and never seen these explained on anty of my courses .. I think most circuits ,sensors on toyota are pull up design . Really enjoyed the video

[@corollagl82]

I am trying to convert an old kettering system into a kettering - mosfet combination. Thanks for this, you just gave me an idea on how i can switch the p channel mosfet via contact point.

[@billyyoder8171]

Thank you Justin. Another great job. Have a blessed and safe week to you and your family.

[@feeneysmechanical6215]

Thank you Justin for everything you do

[@NewLevelAuto]

He's been on a roll eh Greg?

[@alibatebi2161]

on of the best explanation of pull up. pull down circuit. thanks

[@hoaxs1939]

Also known as a Voltage/ Potential Divider Circuit. Great video with very good examples.

[@mikemcmanus2815]

Fantastic video! So efficient, so cogent. Well done.

[@DJ-tn7vj]

Thanks for the video. Appreciate the pull up and down concept that you broke down.

[@nickayivor8432]

Very KNOWLEDGEABLE Thanks 👍 Justin Miller From Nick Ayivor from London England UK 🇬🇧

[@arthurfricchione8119]

Justin you are putting out terrific videos. I just finished setting up some custom probes on my Pico 2205A. Great informative video. This video is also very informative and clearly explained. Thanks for taking the time to share your knowledge. 👍👍👍

[@JustinMillerAutomotive]

I'm glad it was helpful. Thanks for the kind words.

[@asdautomotive8909]

Buena explicación de señales de entrada . Pull-up Pull-down

[@DylanRabier]

Great video! GM wiring diagrams will show you the symbol for a pull up or pull down resistor.

[@adelsharaff2362]

thank you so much. I was so lost, not anymore.

[@AutoDiagnosticsPK]

Great lecture Justin ❤....one request, please keep your cursor colour darker....yellow colour was making it difficult to follow you

[@mohsinshaikh9513]

Amazing video. Very valuable information

[@moparnut6286]

Man I love these videos very educational thank you!

[@jgeorges3061]

Thank you Justin for awesome information really appreciate ur time by doing this.cheeers

[@francisdsa6790]

Exelent professional demonstration thanks 💐🙏⭐⭐⭐⭐⭐

[@frankyv5999]

thank you sir, for your time and knowledge

[@Mewanrahnam575]

Keep going Sir..if you can you please do a tutorial on CAN harware circuit and workings

[@Tubecraft1]

thanks for the vid ,I have one question in the door lock example how is it a pull down when the door lock switch applies voltage to the ECU ? have I misunderstood

[@matthewmiller9855]

Hello, I really like your videos thus far. Thank you for taking the time to do this for us. I am confused though. I am still very new to this. So I reserve the right to be wrong. I am currently going through scannerdanner's book. What you call a pull-up circuit, he calls a pull-down circuit and vice versa. He says if voltage is from an external source then it is a pull up circuit. Reason being that if the switch is open then the sensing circuit will read 0V when the switch is closed the sensing circuit is "pulled up" to source voltage. Now I am more confused. Maybe it doesn't matter what we call it as long as we understand the circuit. Thank you again.

[@JustinMillerAutomotive]

Mathew, I am glad that you are curious! I hope this helps: Without the book in front of me, I am not sure what exactly ScannerDanner is trying to communicate. However, when you use a resistor on an input circuit like this, they are classified as either '"pull-up" or "pull-down" resistor circuits. This video correctly labels them. In a pull-down circuit, the pull-down resistor holds the logic signal to zero volts (0V) when no other active device is connected In a pull-up circuit, the pull-up resistor holds the logic signal to a reference voltage (usually 5V, 8V, or 12V in automotive applications) when no other active device is connected Here are a couple of links about it: www.circuitbasics.com/pull-up-and-pull-down-resistors/ circuitdigest.com/tutorial/pull-up-and-pull-down-resistor

[@jche4503]

easy way to put it is mechanical or hydraulic switches as fuel injectors are pull up/ power comes from external source grounded at computer. gm fuel pump is pull down power comes from computer and external grounded. what mr miller is referring to is a hall effect sensor or electronic switches like cam shaft or crankshaft sensors. scanner danner goes into detail about these in his premium. mr miller is not explaining what type of switch he is referring too. theres mechanical, hydraulic, and electronic switches

[@spelunkerd]

@@jche4503 When we talk about pull up or pull down, we need to remember which resistor we are talking about. The designation in the microelectronics world refers to the actual resistor inside the PCM, put there to give stable voltage even when the switch is open, and to limit current when switch is closed. But in Paul's lecture series I believe he was talking about how the actual sensor, like a fuel pump or temp sensor influences the incoming voltage. I like his idea to identify the two general kinds of circuits, but muddy use of specific terminology can lead to confusion as well. It may sometimes be better to use the terms 'ground side switched', or 'power side switched', for clarity.

[@jyao5409]

The pull up resistor and pull down resistor are clearly defined. I associate pull up circuit with pull up resistor. And pull down circuit with pull down resistor. This is different than the ground side switched or power side switches circuitry.

[@bernardocisneros4402]

@@jyao5409 That's the best way to remember it.

[@AldiShuli]

Great information, thankyou.

[@totbob8947]

Good explication

[@paulalmquist5683]

your yellow circle pointer is very hard so see against the light yellow background. Make it darker like blue or black for better contrast, better visibility.

[@lugmgrm2835]

Excellent ! Thank you

[@shrikantgupta4255]

Well Explained

[@alibatebi2161]

thanks for very interesting video. so that`s why when cooling temp sensor is unplugged the cooling fan starts working because it default to 5v.so it is pull up design?

[@JustinMillerAutomotive]

No, that is not necessarily true. The output circuit is independent of the input circuit. That may be a fail-safe programmed into the computer so that the engine does not overheat if the sensor circuit has a failure.

[@udaysubramaniam2530]

Thank you so much!

[@mikeadler434]

👍👍

[@hichamsaid9472]

Dear sir I have a question about the three-wire sensors (we suppose it works with 5 v), when we unplug the connector from the sensor, we get 5 v or zero volt on the signal wire I am so confused.

[@JustinMillerAutomotive]

It all comes down to understanding how voltage drops in a circuit, including knowing where voltage drops (or doesn't drop) when the circuit is open. The input circuit is a voltage divider circuit. When you unplug the connector from the sensor, the circuit is open and voltage will not drop across the internal resistor in the computer. Because of that, you will get either 0 volts or 5 volts depending on whether it is a pull-down or pull-up circuit.

[@hichamsaid9472]

@@JustinMillerAutomotive thank you so much

[@vincentlee2460]

Its 3.33333v and not 3.6 v at video 3:11

[@sheerwillsurvival2064]

Every video I watch seems to say something different. High side switched or low side switch. And scanner danner says pull down when you unplug goes to 5volts 🤦🏼‍♂️

[@JustinMillerAutomotive]

I have not personally heard Scanner Danner say this, but others have told me that he is teaching it backwards. Don't hold that against him. He's still a very good teacher. Everyone makes mistakes and learns as they go. It doesn't take very much research online to confirm that a pull-up resistor will default to 5 volts when unplugged and a pull-down resistor will default to zero volts when unplugged. I have been teaching for over 20 years and have certainly taught some wrong principles along the way! I hope I am learning and getting smarter as I go!

[@bernardocisneros4402]

Instead of thinking about it as a pull up or pull down circuit, think of it as a pull up or pull down resistor, and where the resistor is located determines if it's a pull up or pull down circuit. If the resistor is connected to ground (negative), then it's a pull down circuit. If the resistor is connected to voltage (positive), then it's a pull up circuit.

[@hammerhead6537]

Excellent! Thank you.

[@JustinMillerAutomotive]

You are welcome!