A Pulldown Resistor brings a line down to a voltage (Typically Ground Potential), while allowing the line to be pulled up.

learn more… | top users | synonyms

1
vote
1answer
63 views

External pull down device required, How much?

In the datasheet for a MCU, it is mentioned that TM "Test Mode" pin require an external pull down device. But there is no details: If I will put pull down resistor, what value should I choose then ?
0
votes
1answer
104 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)
2
votes
2answers
103 views

Pull down resistor on logic gate input

I would like to use a pull-down resistor on the input of a NOT logic gate. I am using a 5V microcontroller, and I want to ensure that the input of the gate will never be floating (eg. microcontroller ...
0
votes
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 ...
0
votes
0answers
45 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 ...
-2
votes
1answer
136 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
votes
2answers
337 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
531 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
1
vote
1answer
34 views

Pulldown doesn't seem to affect inverter?

I have a relay/optoisolator circuit which is connected to a microcontroller. The input/output is controlled by a physical slide switch. I expected this to turn off the relay and status light ...
-1
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.
1
vote
2answers
101 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 ...
7
votes
2answers
461 views

Why does atmel use 39R pull-down resistor?

I recently bought an SAM4S XPLAINED Board to get a bit experienced with ARM. There is an external RAM on this board and there is a 39R pull-down resistor on PIN6 which is the /CS1 line of the RAM. ...
1
vote
1answer
45 views

Question about comparator MAX912 latch enable

http://www.hep.uiuc.edu/cleo/trig3/boards/tile/vme021d_data_sheets/max912.pdf I am using this MAX912 as comparator. There is a latch enable in this circuit which according to the datasheet, output is ...
1
vote
2answers
81 views

Safely connecting GPIO input to output

I'm working on piece of software for Raspberry Pi and I'm writing an integration test. One of the cases requires that I'm able to read a state of one pin on another (basically if one output pin is ...
2
votes
1answer
271 views

Enabling Freescale IMX6 pull down registers on an input pin

I'm looking for a way to enable the pull down resistor on a Freescale iMX6 MCU. I'm running a Linux distribution on it and usually interact with the hardware using a higher-level language, so I'm ...
0
votes
3answers
69 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 ...
0
votes
2answers
67 views

Isolating GPIO's using diodes

Schematic The arrows are GPIO's I want to be able to close multiple switches at once in any particular order in order to manipulate GPIO's manually. I could give each GPIO its own resistor, but when ...
0
votes
2answers
140 views

does CompactRIO modules have builtin pull-up/down resistors

I have Compact RIO 9076 with 4 different modules: NI-9205 (Analog Input), NI-9264(Analog Output), NI-9402 (Bidirectional Digital I/O), NI-9403 (Bidirectional Digital I/O). I have several 3rd party ...
1
vote
1answer
1k views

FPGA floating pins, when place pull-up/down resistor on Input or Output

I've looked my FPGA datasheet and found that there is no pull-up/down resistors on it's pins(just a pull-up but that need to be enabled). So, when I power up my circuit I've for a "big" amount of time ...
0
votes
1answer
173 views

Is it possible to detect high impedance at FPGA input?

I am using a FPGA development board which have neither pull-up nor pull-down resister at the input side. VHDL code that I am developing has to detect either logic zero or logic one and to do ...
0
votes
2answers
295 views

What is the wiring for a pull-down resistor on the Or gate?

Is this wiring and resistor the best choice as a pull-down resistor? Is it necessary to put the pull-down resistor(s) on all inputs and outputs? I put a 10K Ohm resistor connected to the chip ground. ...
1
vote
2answers
1k views

What does pulldown resistor from Arduino's output pin to ground do? Is it necessary?

I came across the first picture below. But I am not able to find out how such arrangement is necessary or beneficial when you want to switch a load with an N channel MOSFET? Question number 1: Is ...
0
votes
3answers
66 views

Low leakage current methods of initializing pin inputs at power up

Suppose I have an IC that has a standard level triggered input pin. I need this pin's state to be setup immediately at power on at a time when my MCU's GPIOs may not have established levels. What are ...
0
votes
3answers
500 views

Pull-down resistor ; why is it crucial

These 3 diagrams represent 3 test cases. Dia 1: When I perform an analogRead of analog port 0, then I get a high value obviously. According to the manual, the <...
1
vote
3answers
418 views

pull down resistor in PIR circuit

I have an motion sensor circuit. The circuit calls for a voltage of 2-15 dc volts. On the PIR data sheet the source pins calls for a pull down resistor of 47K at 5 volts. My question is if I use 8 ...
0
votes
1answer
544 views

Connect arduino to COM pin of a NO NC button

I probably have a basic question but i'd like a confirmation on my solution. I have finished my arduino breadboard prototype which is using some basic momentary push buttons along with pull down ...
0
votes
2answers
80 views

Why does my mainboard power the cathode to turn the Power-LED off?

Close to all desktop motherboards have a pin header that is supposed to power an LED on the front of an enclosure with to indicate that the computer is on. In the documentation for my board, these ...
0
votes
1answer
187 views

Weak pull down for SPI

I am using Arduino(does not matter) and 8 x 12 bit-ADCs to read some values. I created a prototype which consists of a Shift Register(SR) and all outputs of SR are connected to individual ADC's chip-...
1
vote
1answer
118 views

Pull down/pull up resistor for 5v input

I need to implement a pull-down resistor for a project, but I am unsure of what resistor to buy. My circuit deals with 5v inputs. Essentially, I am trying to make this: keypad scanner. Here is a ...
0
votes
2answers
265 views

How to detect input voltage change on specific pin of atmega32? DC jack sensing

I am trying to make an LCD circuit that, eventually, will control an amplifier and display data to the user through the LCD. One of the features I want to include is the ability to show if the device ...
2
votes
2answers
241 views

Simple SPST Switch Circuit - Pull-down Resistor VS. Current Limiting Resistor

Super Noob EE question: Here is my quick draw-up of my SPST switch circuit schematic. I know I probably did not do this right, but if it gets the idea across, then thats good enough for me atm. ...
4
votes
1answer
260 views

MCU pull down input push button with interrupt ESD issue

I have an MCU operated at 3 volt with an input pin that is floating by default. I have an external pull down circuit with a 10K resistor connected to the I/O pin. I also have it tied to VCC using a ...
0
votes
0answers
71 views

How much resistance should a pull resistor include? [closed]

How much pull to ground resistance do I need? Is the amount you need variable? How did you figure this out? (Where can I learn too) Any references I should look to? So sorry for my large host of ...
2
votes
1answer
225 views

LED's connected to a relay remain on?

I built a simple project with an Arduino board. I use the board to read analog input values from a rotation sensor (potentiometer), and use the values to determine which SSR relay on a module to turn ...
0
votes
3answers
111 views

Turn pull-up into pull-down

I have come across the following problem a few times in the past: You have a break-out board where some pins have already been pulled up or down for convenience, e.g. RESET pulled high to keep the ...
4
votes
1answer
756 views

Placement/Location of pull up / pull down resistor?

I have connected a microcontroller GPIO pin, which is intended to be an output, to a DC-DC converter's active high Enable input pin. Since this pin is active high, and because I do not want this ...
4
votes
3answers
967 views

Experiment with pull up/down resistors gives unexpected results

The wikipedia article on pull-up/down resistors provides this image: along with some explanatory text: ... the circuit shown [in the picture] uses 5 V logic level inputs to actuate a relay. ...
0
votes
3answers
208 views

What is the need for a pull-down resistor in this schematic?

here at the second page: http://www.skyeinstruments.info/index_htm_files/W200P%20Windvane.pdf there is an external 470k resistor in parallel with the measuring device. it seems like the manufacturer ...
0
votes
1answer
135 views

DS1302 realtime clock - pulldowns required?

I'm trying to wire up a DS1302 realtime clock, one of these: to a parallax propeller board. The datasheet says (page 4) that pulldowns are integrated into each of the main lines (looks like 3 ...
0
votes
1answer
359 views

GPIO Pin configurations [duplicate]

I went through the data sheet of STM32F4 and found the pin configuration of GPIOs. I dont understand the difference between these configurations. • Input floating • Input pull-up • Input-pull-down • ...
1
vote
3answers
408 views

Do I need pull-down resistor on Enable pin cd74hc4051

Can I directly connect enable pin to ground? I am not going to use it. datasheet Also can I connect all unused pins of LM324 op-amp to ground through single resistor or what configuration does it ...
28
votes
5answers
24k views

When to use pull-down vs. pull-up resistors

After learning and experimenting with microcontrollers, I've understood the concept of pull-up- and pull-down resistors. I now understand when and how to use them, and how they work. I've mainly used ...
1
vote
1answer
547 views

Using an internal pull-down resistor on a microcontroller

I am using an STM32 microcontroller. If I configure a pin as input with a pull-down resistor for use with a button, do I also need to put a resistor between the input pin and VDD?
0
votes
1answer
103 views

The proper way to store bits in JK flip flops [closed]

Currently I'm working on a contraption where when a button is pushed, it briefly creates a 4 bit binary sequence. I want to have this binary sequence, 0000 all the way up to 1111, stored properly in ...
0
votes
3answers
980 views

Solar cell powered supercapacitor charger with strange output voltage regulator problem

I have a strange problem in a low power circuit design. I designed a buck-boost converter as a maximum power point tracking circuit (control the output of solar cell within a small voltage range ...
2
votes
3answers
319 views

Murata OKR-T/10 pulldown value

On the Murata OKR-T/10, the data sheet specifies a 49kohm pulldown resistor but I've seen people using a 1k. Is there a more correct value or does anything 1k or above work just as well?
1
vote
1answer
163 views

Effects of “loading down” Voltage-Divider Circuits

Hello I am currently a beginner in the world of electrical engineering and would like some help on voltage-divider circuits. My question mainly concerns the "loading down effect". Can someone please ...
-2
votes
2answers
552 views

Voltage divider circuit and the Pull-down resister

I am reading about the pull-down resister here. Question 1. The circuit schematic of a light sensor using a voltage divider circuit is shown as: LDR has a resistance of 0.5k\$ \Omega \$ in ...
1
vote
1answer
711 views

How do you size pull-up/down resistors? [duplicate]

The attached photo is pulled from a Piccolo DSP reference design from TI. They use 57.6k pull-up resistors and 2.2k pull-down resistors to allow configuration of boot pins at startup. I've seen all ...