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Questions tagged [pullup]

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

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A FPGA I/O is connected to the OE# of a transceiver and I want to ensure that OE# is high (>=2V) when the system powers up and until the FPGA is configured. The system is battery powered and the ...
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Why shouldn't the resistance of R3 be less than 100 ohms? (See note 12 mentioned at the bottom of the image.)
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I created a schematic for the MAX3485 with the ESP32, but I have a question about the selection of biasing resistor(R39,R40) values. Some people use 4.7k, 10k, and 20k ohm resistors, but I'm unsure ...
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I am building a custom charging panel that will sit behind our couch. It has four DIY USB-C cables that can be pulled out to charge phones. Under the panel, they connect to a 5V power supply rated for ...
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I would like to detect if my DRC-40A is supplied by mains (220v AC) with an arduino nano esp32. I thinked in this two options: Is it better A o B? I also want to keep safe the Arduino's 3.3V. The ...
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I am designing a stand alone board which contains only AD5941. AD5941 contains SPI interface. STM32 board is used for communicating with AD5941. Cable assembly will go from STM32 board to SPI ...
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I am designing a PCB board with an ESP32 and multiple I2C devices on the same I2C line. One I2C device is an RTC (Real-Time Clock) chip, which is included in my board design. I will take the chip and ...
Ahtisham A's user avatar
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In Xilinx's 7 Series FPGAs Configuration User Guide (UG470), they say M[2:0] determine the configuration mode. Connect each mode pin either directly, or via a ≤1 kΩ resistor, to VCCO_0 or GND. Adding ...
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I am building a square wave generator with a ne555. The datasheet in section 6.3.2 Astable Operations has an example circuit that is essentially the same as my practice circuit but with a 1k pullup ...
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I am new to electronics and I am trying to build RGB LED which can be controlled with buttons. Each button toggles red, green and blue value respectively. I am stuck with buttons, I am trying to make ...
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I am trying to make a power up sequence for a sensor that requires 3.3V, 5V and 10V. 5V and 10V power should be applied after 3.3V. My PCB is powered by 12V, and I use STM32L4R5, connected to the EN ...
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I drew a schematic of connecting button to GPIO with input mode with built-in pull up / pull down resistor: Is it a true connection? if it's not, can you fix the problem? The thing I want to do is so ...
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I would like to utilize the bootstrap design of the BeaglePlay board (schematic: link). In case the User button is pressed the GND gets connected to BOOTMODEx. What is the role of the diode(s) here? ...
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I understand that "drive output" on this datasheet means that it's the maximum current the IC can source/sink - i.e. if there is something pulling one of its outputs high at a current higher ...
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I’ve been reading the book “Complex Digital Hardware Design” by Istvan Nagy. On page 74 he writes PU [resistors are] typically 3 to 10 times larger resistor value than PD. On 3.3V signals a 10k PU ...
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I am currently trying to design a circuit that makes it possible to either pull up a line to 5V or pull it down to ground depending on the signal of a microcontroller. The resistor needs to be 1K to ...
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I am designing a circuit that uses two IC's on the main PCB and a matrix of 8 I2C devices connected in a string. These devices are all on discrete boards and have internal level-shifting and their own ...
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I am making measurements for the characterization of pull-up and pull-down resistances in microcontrollers GPIO interface. I am currently working on a STM32 microcontroller, and in particular the ...
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Both of my 'Cube-like' SN4-N2 Inductive Sensor (NPN NC) LED go slightly 'Dim' when activated. I need the LED to turn Off/On when activated. I've tried 5K6 and 2K7 resistors with little change in LED ...
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Regarding this power multiplexer IC's the digital inputs D0 and D1, the input impedance of the D0 and D1 is not given. Only Input current at D0 or D1 is given as 1.4uA. So far I ended with the ...
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I have a charging system based on the IP3212 (diagram below) charging will be done via USB Type-C, the current should be within 1.5-3A (depending on the battery that the user puts). I have questions ...
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I'm working with the eval/dev-kit of the RA8D1 MCU and the external memory bus on their schematic has 4.7K pull-ups on the 16-bit SDRAM data-lines. (from https://www.renesas.com/en/document/sch/ek-...
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I'm level shifting a 5 V signal to an ESP32's input GPIO. I'm using a 2N7000 MOSFET in that way: The input signal has this shape: The LOW pulse lasts 40 μs. I've calculated a pull-up resistance of ...
PaoloRos's user avatar
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I have connected Digilent PmodENC board with a rotary shaft encoder to myRIO MXP DIO pin. MyRIO has an internal 40 kOhm pull-up resistor. On PmodENC board each encoder output has 2 resistors with ...
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This is my first project: Do you think that all the pull-up and pull-dwn resistors value are good? Do the capacitor are oversized? Any suggestions about the circuit in general? Thank you :) Updates:
PaoloRos's user avatar
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Like many others I'm in software so apologies in advance if the question sounds dumb. I watched some videos, read some articles and also read some answers here, such as: Pull-up resistor clarification ...
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I'm trying to use a water sensor in a new design, and I don't understand the example circuit that is given in the datasheet, even though it looks very very simple. I must be missing something. Any ...
Open_Hamster3337's user avatar
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I’m using an ESP32-S3 to communicate with a 5V-only LCD module with an i8080 parallel bus interface. To shift the levels, I’m using the SN74LVC8T245 bidirectional level shifter. This means I can both ...
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I have been trying to design a 2-way active crossover, with low-pass and high-pass channels. So far I got the desired frequency response but the transient response is not up to mark. Here is the ...
Sajil's user avatar
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So, currently we are having problems with the I2C Communications on our cabinet Each row on the cabinet has 5 boards which have 2 16bit io expanders each board has 32 devices and there are 4 boards in ...
reppp's user avatar
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I have these devices: Sensor Keyence FS-N41P Camera Flir Blackfly S Controller Teknic Clearcore The sensor triggers the camera and the controller. The controller supplies 24V to the sensor. This is ...
Martin Henne's user avatar
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I am trying to grasp the idea of an Open Circuit/Open Drain, but I haven't been able to find, which other types of outputs exist ("Closed Circuits", so to speak). It would be helpful, if you ...
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Good morning, everyone. I am exploring the transition of the receptacle from a micro USB connector to a USB Type-C. Initially, my plan included implementing both sink and source capacity. However, ...
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I'm considering upgrading my dad's old tablet, which currently has a micro USB connector. The issue arises from his habit of frequently misplacing the charger, and I'd prefer not to rely on an ...
condor12's user avatar
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2 answers
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I cannot seem to make the schematic below work. As you will plainly see, the idea is to use the PNP as a switching device for a PhotoMOS (TLP354x). By switching SW1, Q1's base goes to the ground ...
VoltsAndNuts's user avatar
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I am learning to design buck converter, and I'm using a LM70880-Q1 buck. There is power good pin available and I want to make use of this pin. It is an open collector output that goes low if the Vout ...
Virtualworld 's user avatar
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Datasheets usually specific pin leakage current for digital inputs in the Electrical Characteristics, which is generally in microamperes (µA) range. I understood from different SE posts that the ...
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I´m using the LSM6DSR accelerometer/gyroscope from ST on a project. Looking into the application hints, it suggests using a 10k resistor as pullup for SDA AND SCL: Since I´m using another slave (...
DMinatto's user avatar
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3 answers
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I'm designing a circuit containing a button with a pull-up/pull-down logic depending on whether I'm grounding a header. The button triggers a GPIO that will detect if the header is grounded thanks to ...
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I am using GPIO expanders (MCP23017) for an array of buttons. Each button is connected between GND and an input pin of the expander. I've enabled the 100k internal pull-up resistor on the MCP23017 (...
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I'm trying to repair a "Flexineb E2" veterinary nebuliser for somebody, it holds a charge and works plausibly well if the battery connection is briefly interrupted but will not power-on if ...
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I started investigating this circuit. The circuit is used to detect another PCBA when it is plugged in as the signal IN# and sends the signal IN#_BUF to the microcontroller. The issue is sometimes the ...
WUP's user avatar
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I have a 12v automotive electrical system that has a pressure switch that switches at 40psi. It is normally closed to ground (low pressure), and goes open when switched (high pressure). The switch ...
Chris S's user avatar
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I'm feeding a BCD diode matrix of switches with Vcc at 3.3 V and running the BCD outputs into GPIOs on the ESP32-C6. The plan is to set each GPIO input to internal pull-down so I can pull it up ...
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I am building this AND gate, and I managed to get it to work properly. However, I had to increase the value of the pull-up resistor to 3 megohms which is too big for what I need. However if I don't ...
Jake's user avatar
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I am trying to build a full adder with NAND gates. I have a transistor implementation: I am getting the wrong output voltages for Cout and S; is there a way to fix this? Is it my resistors that have ...
Jake's user avatar
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I have a Hall-effect sensor with an open-collector output rated for max. 25 mA. This sensor will be used to switch an NPN transistor powering a 12 V LED strip. The load is 300 mA. Could I get away ...
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I have an enable pin that i want to drive high always except when a limit switch is closed, and at the same time I want to monitor the state of the limit switch So is that possible with input_pull-up ...
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I need to shift a 3.3V, push-pull SPI bus from my STM32F3 controller up to 5V to drive a MAX7219 LED controller. To do this, I aim to use an NVT2022 level shifter, datasheet here. The first paragraph ...
kiryakov's user avatar
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I have a circuit where I want to drive the CS# input on a SPI flash chip from an output pad on an FPGA. The flash IC's datasheet recommends putting an external ...
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