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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43 views

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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4answers
114 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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48 views

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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2answers
125 views

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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1answer
37 views

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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3answers
138 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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52 views

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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1answer
96 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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2answers
109 views

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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583 views

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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1answer
59 views

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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3answers
261 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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70 views

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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2answers
77 views

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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2answers
285 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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3answers
57 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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3answers
89 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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2answers
121 views

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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88 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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1answer
77 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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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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1answer
87 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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2answers
271 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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1answer
127 views

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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2answers
335 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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2answers
102 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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29 views

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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446 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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6answers
133 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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833 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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2answers
46 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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6answers
5k 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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1answer
92 views

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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1answer
219 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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83 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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1answer
53 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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1answer
51 views

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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1answer
75 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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1answer
83 views

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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1answer
84 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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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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2answers
161 views

Consequences of leaving unused inputs of clock buffer floating. Alternative: best practice

I'm using a Si53342-B-GM Original datasheet download at silabs for the si5334x-series as a clock buffer. In some cases I only need to distribute a single clock signal and in some of my cases I ...
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3answers
560 views

Why does a pull down resistor eliminate floating input

Ever since I connected a button to an Arduino for the first time, I've wondered how does the resistor prevent floating input from happening? I've read several answers to similar questions, seen videos ...
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1answer
870 views

Floating input in Op-amp Readout Circuit?

I was analyzing this circuit diagram in a thesis about a capacitive EEG electrode. The author talks about a flaw in the design where there is a "floating analogue input" that is causing the op-amp to ...
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1answer
54 views

Isolated power supply with output on a 2kVDC floating ground

I am building a system of detectors which are referenced to independent floating grounds. The maximum voltage between each stage is 2kVDC. So I need isolated supplies which can operate continuously at ...
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1answer
234 views

Floating neutral in TN-S or TN-C-S earthing system

Since neutral is bonded to ground at building distribution point in a TN-S or TN-C-S earthing system, could floating neutral happen under the following conditions: Loss of N and/or PE at transformer ...
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8answers
5k views

What is the right way to float a home lab?

I just got myself some new toys for my lab at home like 30V DC power supply, KKmoon signal generator and a Rigol DS1052E. I want to float everything, because I don't want to spend any money on stuff ...
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320 views

Is it possible to get a floating power supply to power multiple MOSFETs

Hey guys this is my first post on stack exchange so please go easy on me! I have a hobby project where I was trying to make a few batteries go in series using a micro controller and a floating power ...
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1answer
173 views

Can I leave it unconnected pins in the level shifter?

My concern is that pins are connected between DB25 and TXS0108E, but are not connected between TXS0108E and the Header 5x2. There is only the tracks between TXS0108 and the Header 5x2, but there is no ...
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1answer
620 views

Floating DC power supply (solar panels) - do I need double-pole breakers and why?

I am in the process of building a small off-grid solar setup. There will be 4 parallel strings of panels in this setup, and I understand that for 3 or more strings, you need some sort of over-current ...