A Pullup Resistor brings a line up to a voltage (Typically VCC), while allowing the line to be pulled low.

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1answer
28 views

NPN BJT non-inverting simple amplifier [on hold]

How to use an NPN BJT as a non-inverting amplifier with a pull-down resistor? (as opposed to using it as in textbooks as an inverting amplifier with a pull up resistor)
1
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2answers
39 views

12 Vdc Intel fan tachometer output to 24 Vdc PLC input

I'm working on a cooling fan rotation supervision system, and I'm planning to use my old 4-wire Intel E18764 12 Vdc cooling fan to test it (as I don't have access to the 24 Vdc actual fan I'm going to ...
0
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1answer
93 views

Pull up/Pull down power consumption [closed]

For a microcontroller, does pulling up a GPIO pin consumes more power than pulling it down? (I've got the option to pull a GPIO pin up or down)
0
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3answers
70 views

Does several PIC12F683 pull-ups cause short circuit

I am connecting several PICs together by GP4 and GP5 pins, and I used their internal pull-ups to make pins high by default. If in all PICs pull-ups are enabled. Does connecting a lot of PICs together (...
0
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1answer
75 views

Open Collector Circuit Needs Pull-Up Resistor to Measure Frequency?

I need a little help determining what I need in order to measure frequency from an Encoder containing the attached Open Collector Output. The 5 Volts will actually be 24 Volts in my scenario (this is ...
2
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0answers
26 views

MCP4131: How to know what value resistors to use on the multiplexed SPI IO?

There are two aspects here. The first question is related to R1 below: The datasheet says: "R1 must be sized to ensure VIL and VIH of the devices are met" but gives no formula. So first question: (...
2
votes
1answer
87 views

I2C ideal pull-up resistor calculation

As part of a test i was given the following question: My attempt gave an incorrect answer. The "correct" answer is 1000 ohm but i am having trouble figuring out why. My interpretation; min value ...
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votes
3answers
56 views

Arduino Mega Pull-up on Analog input

does Arduino Mega2560 (based on ATMega 2560) has an input pull-up on analog inputs? Can I set the input pull-up as usual by software? The reason is that I need to use the analog pins as extra digital ...
0
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2answers
49 views

Understanding pull-up resistors and the 7489 memory chip

I have been learning about the 7489 memory chip. I had two of these that turned out to be broken (see here for previous question on this). I got more and I have finally gotten everything to work. ...
2
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0answers
51 views

PIC32MX350F256 Errata , IO open Drain Issue

In one of our Product we used Microchip micro controller ā€œ PIC32MX350F256Lā€. Attached image is small part of circuit showing uC interfacing with a SPI device. We are using bit banging communication ...
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0answers
33 views

Pullup/pulldown configurations for memory I/O lines

I have a custom board with a AM3352 processor, and I am curently configuring the multiplex settings for each pin, and I've stumbled accross a confusing point when configuring the I/O lines for the ...
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votes
3answers
108 views

Microcontroller internal pull up [duplicate]

I was reading microntroller datasheet, they mention any I/O pins can be configrued as Open drain , or as Special pheripheral ( like SPI , I2C etc..) or push pull. Q) Can we enabled microcontroller ...
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2answers
60 views

Considering input pin impedance when calculating pull-up resistor value

When calculating the value of a pull up resistor , i am dividing the Vcc voltage by the desired current value. simulate this circuit – Schematic created using CircuitLab But since ...
3
votes
1answer
88 views

SPI bus termination and pull-up resistors

My microcontroller (ATMEL series) needs to communicate to a slave device using SPI protocol. I am designing the hardware. The maximum SPI bus speed is 1 MHz. The distance between the master and slave ...
3
votes
2answers
98 views

Why do we use pull up resistor with PIC?

I tried to find an appropriate answer for the question but couldn't find what I needed exactly. I found out that "Initially the output from the PIC is floating and we use the pull up resistor R7 to ...
0
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0answers
38 views

BeagleBone GPIOs mode

I want to know what is the mode of BeagleBone white pin if I use it as an input, is it pull-up or pull-down or have both or what exactly, I am a little confused, I had read that it is pull-down and ...
0
votes
2answers
63 views

How to detect pin state change in pulled up pins

I am working on Toradex module and developing a simple application where I am detecting the input and displaying it on UART. Now the application requirement is that we give 12v as input but the ...
1
vote
1answer
96 views

Why do we need a pull-up resistor when there is a floating connection at the base of a transistor?

Let's say that the base is connected to any normal PIC. My teacher was talking something like, "There will be a floating output at the base when nothing is connected so we use the R7 (10k) for safety."...
3
votes
3answers
85 views

How to enable Output pin to high by default in Arduino Uno?

In Arduino Uno, I noticed that when I set a PIN to output, the default initial state is low. Is there a way to set the initial output state to high? The pinmode documentation supports only input, ...
0
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1answer
130 views

STM32F103 GPIO and wrong configurations

I have a few questions about gpio. First What if two push-pull pins with high level connected? My point of view is that there is no way for current and nothing bad will happen. And reading of pin ...
2
votes
1answer
98 views

Why is my pull-up resistor not working?

here's my schematic. I've got this circuit hooked up to those pins. Q1 is P-channel MOSFET (AO3401A), I've also got an ATmega328P not pictured, and POWER_BUTTON is connected to PC4 of the ...
4
votes
3answers
195 views

I2C communication won't start unless SDA pullup resistor is reinserted

I'm working on a project where a PIC12LF1552 microprocessor is using I2C to talk to a TMP75 temperature sensor. Like the title says, a very strange issue keeps happening. Overview Every time I ...
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1answer
83 views

Water Level Indicator

I have built water level indicator circuit as shown in this figure. If the inputs of IC 74148 is connected directly to negative supply through pull up resistor it works, but if it is connected to ...
1
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1answer
51 views

interfacing external push button to msp430 using energia

I am writing code in Energia using the mso430g2553 launchpad and an external pushbutton with a pullup resistor. The code should simply display the state of the button on the serial monitor, 1 for ...
1
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1answer
46 views

To make input-output pin of sensor high from mcu is it better to give logic high from mcu or making the mcu-pin input with pull-up?

I drive sht11 temperature-humidity sensor from mcu, the reference design from MikroElektronika uses the following: To make sda pin high, the pin connected to sda (which is pull-up) is not given to ...
7
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4answers
527 views

What small IC could give switchable I2C pullups?

My goal is to replace a DPST on pullup resistors with something simple, cheap and very small that can be activated with the I2C bus voltage. I thought that this might be a common enough requirement ...
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votes
1answer
87 views

Pull-up resistor causing unintentional voltage divider?

I'm trying to use the output of a comparator as the input of a schmitt trigger built with positive feedback on another comparator. Both have open collector outputs. When the two are not connected, ...
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votes
1answer
134 views

Pull Up/Pull Down Resistor Confusion

I have googled the crap out of this but I can never find a good answer. In a circuit with a pull up resistor, why is the input pin fed current with a resistor? A pull down resistor circuit doesn't do ...
0
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2answers
297 views

Should the output of logic gate have pull-up or pull-down resistor

I am a bit confused whether my chosen AND gate should have pull-up or pull-down resistor on the outputs, as I don't see any sentence containing words like pull-up/down or sink or source ... but as far ...
0
votes
1answer
441 views

stm32f4 pull up resistor value

I'am working with Stm32f4 discovery board , i need to know the right value of the pull up resistor on the GPIO port all there is on the datasheet is : week pull up Thank you
0
votes
2answers
55 views

DIP switch on Atmega32, are external pull-ups neccessary?

I'm connecting a DIP switch to an Atmega32 as shown in the diagram above. This works well in my application so far. However the common opinion seems to be that external pullups are necessary for a ...
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3answers
301 views

Why do we need a pull-up resistor if we can just make a short to the power source? [duplicate]

I saw the term pull-up resistor being mentioned everywhere, but I haven't grasp the reasoning behind its use. For example, I saw one in the book Practical Electronics for Inventors, in this schematic ...
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1answer
130 views

NMOS - Why is a resistor necessary?

I understand how the logic levels of an NMOS work with a pull-up resistor. 1. What would happen though if there was no resistor attached? (What would the logic levels look like and why?) 2. What ...
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votes
1answer
83 views

Pull Up/Down vs High/Low Pull [closed]

Is pull up the same as high pull? Is pull down the same as low pull? If they are different what is the difference? These two terms are all mentioned in this guide and it is kinda confusing.
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2answers
92 views

Pull up/ Pull down resistor

I am using an external pullup resistor on my input pin, and a switch connected to GND. It is like in the picture below. In the below picture, when the switch is open, the MCU input pin will see a ...
3
votes
1answer
69 views

Electron flow with pulling resistors

I'm very confused on the idea of pulling resistors. I get that they set the default voltage to a value so that you don't get a floating high or low value, but I don't get the application in TTL. So ...
3
votes
2answers
259 views

Temperature compensation in transistor current cource

I am working with analysis of BJT current source. I didn't get the explanation of temperature compensation in NPN transistor with PNP and pull up resistor. How does it work actually?
0
votes
1answer
108 views

Pull Up Resistor on signal too low (Tx from HC-06), why it get fixed?

I had problems with a bluetooth module HC-06 because it didnt transmit the data by UART, but someone told me to add a pullup resistor between the VCC and the TX of the module, it works, we tested with ...
3
votes
3answers
115 views

How to avoid Attiny84 being powered on by a pulled up data line?

I've developed a simple sensor board based on the Attiny84a microcontroller which is able to communicate over a serial connection. I'm using an arduino bootloader and the SoftwareSerial library on ...
1
vote
1answer
124 views

How could this transistor be in saturation?

For this RTL circuit (RTL inverter with active pull-up): The textbook says that in the output high state, Qp is in saturation and the circuit looks like: I wonder how this is possible? $$Rcp = ...
2
votes
2answers
755 views

How does strength work in Verilog?

I want to create an assignment which takes care of pull-ups from a port pin. I wrote the following: ...
0
votes
0answers
68 views

LVCMOS33 to LVCMOS25 using a diode and pull up resistor

I am trying to interface LVCMOS33 to LVCMOS25 without using a supply voltage of 2.5V. I was thinking of using a schottky diode and a pull up resistor. I am trying to do this to two signals; ...
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votes
2answers
102 views

about getting the ACK right in TWI

okay, i'm an old EE that mostly just writes DSP code and dinks around in MATLAB. but once in a while i get to dabble in more concrete things. and, actually, this TWI-bit-banging code seems to work, ...
0
votes
1answer
118 views

Voltage divider with pull up resistor

I'm trying to trigger a logic fall signal on my raspberry pin input which is set with a internal pullup resitor (on 3V). The input raw signal I have in actually a 0V which change to -5V during a ...
1
vote
0answers
243 views

What happens when you use internal+external pull-up resistor?

I was working with an Arduino One and this rotary encoder from SparkFun. Then, for no good reason, I put three pull-up resistors, one for each input pin (pin 2, 3 & 4) facing the encoder, like ...
0
votes
3answers
67 views

Can this active-high scenario be achieved without an external pull down resistor

If I understand correctly, few microcontrollers offer internal pull down resistors on their input pins but almost all allow for internal pull up resistors to be configured. Why exactly is that ? I ...
1
vote
4answers
312 views

What is the purpose of a pull-up resistor in a microcontroller?

I'm reading about the AVR microcontroller. In a chapter on I/O ports I've stumbled accross a concept that I have trouble understanding: the pull-up resistor. Here is a quote from the textbook: ...
0
votes
1answer
105 views

Tristate logic equivalent in NMOS logic

Suppose I have 3 signals generated by NMOS logic. Each of those signals has an associated enable pin that when driven high will result in the value of the signal appearing on the output (I should note ...
4
votes
1answer
100 views

Pull up resistor in NMOS logic value

For my senior high school project I decided to build a basic CPU from discrete components. I plan on using a 5V logic level and the current design calls for around 2000-3000 N-channel MOSFET ...
2
votes
3answers
644 views

Why are pull-up resistors required to be connected to the 2 lines of I2C? [duplicate]

Without pull-up resistors connected to the 2 lines of I2C, I2C communication fails. Why is there a need to have pull-up resistors for I2C? In contrast, UART and SPI do not need pull-up resistors. ...