Questions tagged [floating]

A voltage that is not connected by any conducting path (including resistors) to ground or the key voltage reference point.

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How to drive multiple floating N-channel MOSFETs

I want drive a RGBW-LED (CREE XLamp XM-L) using a synchronous constant current buck. To control the brightness and color, the LED of each color channel is controlled by a shunt transistor using PWM. ...
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Microchip FPGA Internal Short Circuit

We are using the FPGA ProASIC3E A3PE1500-PQ208. The FPGA got internally short circuited during runtime. The FPGA IO Supply Voltage and FPGA ground are permanently short circuited and it is not ...
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Vl53l0x ToF Sensor turn on without gnd

My ToF sensor turn on if I not connected its ground pin to common ground (I let it float). Why?
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Tying open-collector outputs to TTL inputs

I know that open collector outputs are effectively either 0 V or high-Z. I also know that TTL chips tend to read a disconnected output as high, but that really you should have something like a 1 kΩ ...
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Why is the voltage across high impedance indeterminate?

The analog pins on my Arduino read sporadic values when unconnected, and my multimeter (set to VDC) shows random values when there's no connection between the probes. If I connect the analog pins on ...
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Do disconnected input pins act as “antennas” capacitors that get gradually charged, building up higher and higher voltage?

Disconnected input pin acts as an antenna affected by surrounding electromagnetic noise, and can "float" between on and off. Does the input pin also act as a capacitor that gets gradually ...
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148 views

Are there logic gates by which a signal could propagate backwards?

Is there a type of logic gate with floating inputs (I'm using that term loosely) such that a fixed voltage on an output could "propagate backwards?" Let me clarify with examples... Say you ...
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6 votes
2 answers
673 views

Counting signal switching between floating and LOW in Arduino

I have a rotating contact (contact breaker of an ICE) that switches between being not connected to anything (floating) and being connected to the case of the ICE. The engine case is connected to ...
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Bias tee for floating DC supply

I have a floating DC low noise current source driving a load. I also need to drive this load with an RF source but the grounds are not referenced to each other so I don't think I can use a standard ...
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Connecting GND on secondary side to protective ground

We have a battery powered equipment which mainly consists of a temperature sensor connected to a microcontroller via a filter. In addition to battery power we have now added the possibility to use a ...
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4 answers
211 views

Is it possible to "stack" the outputs of 2 or more buck converters?

Is it possible to "stack" the outputs of 2 or more buck converters? The buck converter circuit in question I am considering is the 48v to 5v typical example circuit from page 20 of the ...
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Randomly Floating PWM signal

I am having trouble with a randomly floating digital signal. Transmission is between a microprocessor and a CPLD unit and is used to run a half bridge. Measurement was taken after the output resistor ...
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Random activation of transistor base by capacitive coupling (ghost voltage)

I have a smart module used for home automation. It is equipped with two relays, a wifi mcu, and two switch input. For the switch input it uses AC mains detection using transistor (non-isolated.) In ...
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1 answer
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What does "Default Output State" mean for a digital isolator?

I do not understand the term "Default Output State" of the SI8422AB-D-IS digital isolator. I saw it on this datasheet at page 3: Does it mean "the default output voltage if the input ...
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-1 votes
3 answers
249 views

Why does an LED remain glowing when MOSFET gate is open?

Hello, I'm working with an N-Channel MOSFET (Link to data sheet for the MOSFET - https://www.onsemi.com/pub/Collateral/FQU13N10L-D.pdf) for the first time on a DC motor project, and I'm trying to ...
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Floating voltages and current path between isolated circuits

I have a bit of trouble understanding floating voltages. I thought about quite a few circuits and scenarios involving isolation transformers and floating voltages but something is still off. Here are ...
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1 answer
114 views

Strange floating base NPN behavior

I'm learning about NPN transistors and have wired up this: I understand some of its behavior, but one is a complete mystery for me. First, if I tie "B" (green dangling wire) to "G"...
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Dc power supply outputting sine wave at both terminals

I connected a DC power supply (set to 706mV) to a 1kohm resistor as this: The semantic is like: However, strange things happen when I use the oscilloscope to view the voltage waveform at point A and ...
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Confused about opamp's inner "ground"

(well. I am NOT speaking of "virtual ground" throughout this question/) As this figure has shown an opamp can be viewed as: We all know that an opamp like this has two inputs and one output ...
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No unconnected inputs yet ICs (logic gates) still seem to yield erratic/odd behaviour

I just finished building a 4-bit adder on a breadboard and I am experiencing some quite odd/erratic behaviour and I am wondering why. The actual circuit/logic works as intended, meaning the 4-bit ...
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3 answers
340 views

Understanding Differential Mode Voltage of a Floating Circuit?

I am currently trying to work on studying for the ECE NCEE FE exam, but I came across the problem and don't quite understand the answer. Essentially we have an ideal transformer with an arbitrary ...
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What is the correct way to bias a floating instrumentation amplifier?

Im designing a voltage measurement circuit that needs to measure differential signals in the order of mV in the presence of high voltage common mode noise. Im using a isolated DC/DC converter that is ...
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Floating input pin with external pull-up

I would like to improve the performance of my push buttons, which sometimes don't respond when pressed. They have external pull-up resistors and have been initialised as floating input pins. Does not ...
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2 answers
522 views

Floating analog input of ADS1115

I am using an ADS1115 as an analog to digital converter. R2 and C2 are used as a low pass filter. I have used two schottky diodes as voltage clippers to protect against over voltage. To avoid ...
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3 answers
73 views

Floating traces on MCU dev boards bad for noise?

When you have development boards for microprocessors with every GPIO pinned out on headers around the edge of the board, is the board more susceptible to picking up noise than a board without all ...
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141 views

How does a pull-down prevent a "false 1" in a pin?

yesterday I asked a question about pull-ups and pull-downs and resistance in an input pin, but I feel that the question that invaded me today is different from my yesterday's post so this is why I'm ...
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Floating battery negative terminal [closed]

I am building a circuit that uses an op amp comparator stage to control the circuit shown. The op amp circuit will switch on or off the transistor to drive the motor supplied with a set of AAA ...
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154 views

Floating Simulated Inductor

In the image below, I do understand that a grounded inductor can be simulated using op amps. However, to make a floating simulated inductor, I have read some posts that said two ground simulated ...
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1 answer
174 views

Floating Nodes Error in Simulation in ORCAD PSPICE

Does anyone have any insight as to what exactly is wrong with my circuit on Orcad/PSPICE? My name is in the project name so I blurred it out for obvious reasons
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40 views

Battery powered device - How to measure external floating differential voltage

I have the following task. As depicted in the sketch, I have a battery powered device which needs to measure the differential voltage VIN between two external nodes, EXT_NODE1 and EXT_NODE2. It is not ...
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1 vote
1 answer
182 views

What is the result of 1 and float on OR gate?

If only one input is 1 into an OR gate, the output is 1, but does that still count if there is no input from other sources? (like float) Or is the output simply float as well?
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2 answers
438 views

How to get rid of floating voltage on Bridge rectifier

I'm trying to implement a rectifier and AC voltage sensor. The rectifier part works just fine. I'm able to power my device without any issues. Please look at C2 in the screenshot (Circuit schematic)....
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Why does my ungrounded DC power supply work?

This is a question about electronics theory that I haven't been able to grasp. I was testing a stepper motor wired like the following: https://learn.adafruit.com/adafruit-tb6612-h-bridge-dc-stepper-...
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1 vote
2 answers
702 views

Floating Differential measurement?

Can I simply hook up an opamp inputs, (either using a differential or in-amp topology that is/are also powered from a floating power supply), across a device under test that itself has exceeding ...
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3 votes
2 answers
127 views

EMC - conducted emissions - unused wires in cable - puzzling coupling

I am trying to understand the impact of unconnected wires in a cable for EMC conducted emissions tests. My product has a shared unshielded cable for supply and communication (I know it's bad practice....
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1 vote
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Sensing of AC current. Isolation Capacitor Problems?

I want to measure the AC Current flowing through a Piezocrystal (replaced in the circuit with a resistor) being driven by a TI DRV2700. http://www.ti.com/lit/ds/symlink/drv2700.pdf This Chip puts out ...
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3 answers
840 views

About floating ground and circuit problems

Good morning, I have a power supply with floating ground that drives my circuit. Since the circuit doesn't work as expected (it works fine only if the ground is tied to earth) I did some measures with ...
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6 answers
158 views

Is a floating pin equivalent to a very weak pull down?

I know that if a MCU pin is configured as "input" and it is not connected to any pull up/ pull down resistor, it is said to be floating. In this situation, we could say that the pin is in series with ...
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9 votes
7 answers
956 views

Why can a MCU input floating pin easily change state?

I would like a technical ("engineering") explanation of why a MCU input floating pin can easily change its state depending on the outside electromagnetic interference. Is it related to the fact that ...
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1 vote
2 answers
52 views

How to handle disconnected resistive sensor?

I'm trying to connect a PT100 thermo probe to an Arduino project to measure water temperature. After some research I have found and adopted a design using a Wheatstone bridge and an instrumentation ...
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14 votes
6 answers
6k views

Is a pull up/down resistor really necessary?

Logical reading (1 or 0) of a micro-controller input GPIO pin may float if it is neither connected to VCC nor GND; someone said it is because of surrounding RF interference. When a floating GPIO ...
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1 answer
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How can I simulate the circuit with floating node in Orcad simulation?

I simulated to test 4n25 optocoupler. 6 pin in 4n25 is base of output transistor. According to google, 6 pin can be not connect pin (NC) because input LED generate the base signal. Orcad ...
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2 votes
1 answer
388 views

555 Timer Output Always V+ or Ground?

If the output of the 555 timer is not trigger to high, is it ground? Or is the output left floating?
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1 answer
97 views

Floating Power Supplies

Referring to this post, is it possible to float power supplies by simply not connecting the ground wire?
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1 answer
58 views

Constant Offset Floating Supply

What circuits can be used to provide a voltage supply capable of sinking around 1A of current that will always float 10ish volts below a given supply, that could be from 12 to 200 volts? I have ...
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1 vote
1 answer
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Unused/floating pins on BTS5016

I plan to use Infineons PROFET BTS5016 in a coming project. https://www.infineon.com/dgdl/Infineon-BTS5016-2EKA-DS-v01_00-EN.pdf?fileId=5546d4625a888733015aa41a5e161129 I will not use the ...
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0 votes
1 answer
190 views

Floating analog input value

To use my sensor I need to supply 24V. So I converted 4.5 V from battery pack to 24V and converted it again to 0-1.66V using a voltage divider. So far I can read the output of the sensor using the ...
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Micron NOR unused pins have pull-ups. Any danger just leaving them there?

I have a board designed for a dual-die Micron MT25QL512 QSPI NOR flash. These parts are in short supply, but the board fabricator had some single-die MT25QL128, and used them instead. The single-die ...
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2 votes
1 answer
130 views

Measuring small currents at DC high voltages without floating meter

I'm doing a project with a Cockcroft-Walton multiplier that will output up to 40 kV DC at up to 10 mA. The the circuit takes an input of 10 kV AC at 60 mA and 60 Hz (from a neon sign transformer) and ...
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8 votes
3 answers
1k views

How can I float a pin that otherwise should be low?

I want to enable/disable a TI TPS54302 buck regulator with a microcontroller. The enable (EN) pin should float to enable the device, or be tied low to disable it. I currently have the EN pin ...
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