Questions tagged [isolation]

Allowing for the flow of power or information without shared electrical nodes

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Isolated RTD sensor

I need to read a Heatsink temperature with 5KV isolation. how is it possible? are there isolated temperature sensors ? or shall I design a board for it to isolate the output signals?
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Overvoltage and overcurrent protection to digital signal lines

I'm looking for a technology that protects digital signal lines like SPI, I2C, UART and general purpose I/O against overvoltage and short circuit. That is, protects the microcontroller's digital ...
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28 views

Isolating an existing RS485 tranceiver

I have a heat pump with an RS485 interface. Via a simple RS485 chip. No isolated interface, no isolated power supply to it. I want to add a power meter at 400+ meter to it and want to properly isolate ...
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94 views

Isolation Circuit Question - How does this feedback work?

I am completely stumped. I have been troubleshooting this circuit for some time, and is what powers another circuit. The thing is, I have no idea how this thing works (not well as of late, due to ...
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1answer
41 views

Gate driver Isolation

I have designed a 50 W, 12V-5V buck converter operating at switching frequency 200kHz.This is just for understanding practical converter circuits, so I made a totem-pole bjt driver circuit for IRF640N....
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112 views

Current sense resistor for high voltage

I have a 5KV DC output from a Cockcroft-Walton multiplier. The current is around few microamps as per the simulation. To prevent discharge, the 200Mohm resistor holds the voltage of the Cockcroft-...
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1answer
72 views

High Voltage Safety Questions

I'm working on a project that uses 1700VDC provided from a 220V:1200V isolated toroidal transformer, bridge rectifier and filter cap. I have no experience with high voltages, so I'd like to ask you ...
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45 views

How do I reinforce a cardboard antenna for outside use?

I bought Mohu Releaf cardboard antenna. It works much better outside than inside. Mohu explicitly advises against outdoor use of its indoor models, yet I wrapped it in a plastic bag and hung it out of ...
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1answer
91 views

Should I use an isolated DC-DC converter?

I am designing a controller pcb for a wall climbing robot, which uses a ~150W suction brushless motor to stick to the walls and two smaller ~30W brushless motors to move around. The system consists of ...
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1answer
28 views

BLDC motor, typical maximum isolation voltage in DC

For one of 1/3 or 1/2 hp, can I aply a instantaneous 400VDC on it together with PWM (of around 50-200hz), safely? Do commom BLDC motors cumply with that spec?
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Is this a safe way to measure mains power on an oscilloscope?

I wanted to use my cheap battery powered single-channel oscilloscope or my Rigol 1054Z to see the 120V AC mains signal in my house. No particular reason, just curious. I at least knew enough to not ...
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34 views

Transformer isolation and reference

For testing purposes, I need two circuits: 220Vac rectified and 48Vac rectified, both having the same reference, like this: But I don't have an isolated transformer 220V:220V. I only have an isolated ...
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1answer
60 views

Single ended scope probes on equipment under test which ARE on an isolation transformer

I am using my company's new oscilloscope and I don't want to mess it up. I have searched all of the topics, but nothing tells me exactly what I want to know so I thought I would ask in case somebody ...
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Allegro ACS71020 Reinforced Isolation

Based on the diagram on the datasheet, I don't see that the AC line voltage measurement circuit is reinforced isolation. Resistor dividers can't be reinforced isolation circuits as my understanding. ...
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39 views

Rectified DC current measurement using shunt or Current Transformer

I am working on a project to design a controller for battery charging solution. A 3 Phase delta power (440 Vrms ph to ph) is given to a 3-phase Variac Transformer ( Variac is operated ...
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2answers
49 views

Isolation Capacitance (Cio)

How I can find a practical value of CIO barrier capacitance (primary to secondary side) in digital isolators?
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1answer
72 views

Rocker style light switch: do I need an isolated power supply

I'm building a Wi-Fi controllable light switch that will use rocker style (up/down) plastic buttons. My plan is to have all the electronics enclosed behind a metal gang plate (the part that screws ...
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2answers
62 views

Feedback regarding isolation practices on a 5V/Mains PCB

I am currently designing a PCB for a project including PID-control of a heater. The heater runs on mains (220V) and is controlled using zero-crossing switching to regulate the power and minimize EMI ...
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1answer
76 views

ADC eliminating noise for improved accuracy

I am working on a 24 bit ADC and would like to eliminate noise as much as possible in order to maximize the performance of the 24 bit ADC. There are two main areas where I am concerned where noise ...
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2answers
71 views

How do you create an isolated, positive voltage?

I know this seems like a simplistic question, but I am a beginner here.... Multiple web sites pop up on Google talking about how to create a negative voltage, but what about positive? The ...
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30 views

MCP3008/ADuM3154/ESP32 - Corrupted MISO Data Line

I have 3 MCP3008's being read by an ESP32 on the same bus isolated by an ADUM3154ARSZ. I was reading each pin on the MCP3008's about every 10ms. I seemed to have a lot of jitter and after averaging ...
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1answer
35 views

Analog sensor signal isolation for ADC/DAQ

I am looking for the simplest way of sampling an analog sensor signal in an existing system while avoiding ground loops (say 20kHz maximum frequency). The sensor is a 5V supply with 0-5V return signal....
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1answer
56 views

When is it allowed to use non-isolated PoE?

Currently I am designing a circuit that is required to be PoE powered. We are debating whether to use an isolated or a non-isolated supply. The device is wall mounted and in a plastic enclosure. No ...
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1answer
26 views

Transceiver Supply isolation with Transformer

I need to supply the Vcc2 for 2 different transceivers, one for the CAN-BUS, like the ISO1042-Q1 that have a Vcc2 of 5V, and another one (not yet defined) with a Vcc2 of 3.3V. On my PCB I have both ...
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PoE galvanic isolation necessary?

I am currently designing a battery powered LED project, that will be charged and/or operated over 25W PoE+. In my current design, I am using a flyback converter to convert the 48V to 12V and for ...
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98 views

How to protect my sensitive electronics from noise induced by AC power line?

I have a circuit that will be placed in somewhat close proximity to 220 VAC mains power. The mains power lines are bundled together of around 20 pairs (live and neutral) those 20 pairs should total up ...
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28 views

Reading and writing analog voltages to two outputs of a lab bench supply from one microcontroller

I am planning on building my own lab bench power supply which should be software controlled and have two outputs. I am considering using the ATMega2560 due to its large amount of I/O pins, but I don't ...
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50 views

Add isolation to a switching power supply

Actually I'm using a simply switching buck regulator that perform a 24v to 12v convention. I'd like to add isolation between power source and regulator. I've checked already all-in-one isolating DC-DC ...
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386 views

Why does increasing altitude (low air pressure) results in lower resistivity/ breakdown voltage?

I got this question because the creepage and clearance distances need to be adjusted for altitude. The higher the altitude, the higher the distances should be. It seems to me however that the contrary ...
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2answers
48 views

CANbus to USB adapter, is optical isolation worthwhile?

I have a motor whose driver board communicates via the CAN protocol. I need to programmatically command the driver board from my laptop computer using CANopen. I ...
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2answers
58 views

Can galvanic isolation be performed at the user interface (UI)?

With capacitive touch sensing and transparent materials, it seems like it would be possible to run small digital devices from A/C mains without a transformer isolated supply. Is there a flaw in ...
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222 views

In 2020, what are the most common approaches to power-line-communications for hobbyists? (updated)

I'm looking for modern control protocols, designs and/or components to simplify controlling (and running) a very low power system on a chip safely from mains power. I'm in the USA, and on a hobby ...
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1answer
28 views

Timebase Ground-Loops - why place the isolation transformer at the input instead of the output?

In the course of investigating the construction of a home-made 10 MHz lab frequency reference I wondered if the output from such a reference should be isolated. I came across a small article about ...
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4k views

Does power delivery over ethernet always have to use isolated DC/DC converters?

I am examining the possibilities for building a cheap ethernet device that would be powered over ethernet using PoE technology. I came across this article which shows the generic block diagrams: ...
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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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99 views

High Voltage (0-600V) DC Voltage Sensing, Shared Ground with Isolated Converter and HV-

I'm designing a circuit to detect when the voltage across two DC input lines (HV+ and HV-) is greater than 60V. The voltage will vary from 0-600V. A seperate supply of 12v and 5v is available for use. ...
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146 views

How to safely ground a device plugged into an isolation transformer

I am working on an old turntable power supply on my workbench. I have acquired a 1:1 bench isolation transformer to increase safety while doing this. It seems to be a well known "issue" with at least ...
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55 views

What are the specific scenarios that an isolation transformer is useful for avoiding?

I have a home workbench and do minor refurb work with old turntables and monitors (CRT) etc. That implies potential exposure to high voltages (mains or above) at power supply capacitors, etc. I have ...
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1answer
56 views

SMPS Testing: Differential Probes or Common lead and best Grounding practice

I'm testing a Switch Mode Power Supply that is not outputting the required voltage. It's only two prong, hot and neutral, and I wanted to get clarification on the best way to approach measuring the ...
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1answer
35 views

Bidirectional protection or isolation for generic digital communications

I am redesigning a company product, it is a product for automotive maintenance and diagnostics. Currently in the product there is a FET BUS switch to perform the interface between the microcontroller ...
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1answer
60 views

Positive-negative voltage from dual supply

I'm trying to build a low cost hifi (Hiraga Le Monstre) but I have two old computer PSUs at hand so I tried to use it as power source. The Monstre needs +12V and -12V, computer PSUs have both, but the ...
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57 views

Optocoupler voltage drop when connected to load

simulate this circuit – Schematic created using CircuitLab The inverter supplies max 25mA. The optocoupler draws 18mA. The optocoupler is supplying 1.7V to the sensor at node 1 instead of ...
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113 views

What is this Diode for?

This part of a schematic from the I/O board in the link below shows a 1N4148 diode in parallel with an optocoupler's input circuitry. What is this diode for? https://startingelectronics.org/projects/...
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75 views

DC/DC converter with 12 outputs, low noise?

I need to 5V to 5V. It might seem surprising but let me expain. I need to convert a voltage of 5V with 60mV ripple (coming from a PSU doing 120V AC to 5V DC) to say 5V with low ripple. I'm however ...
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1answer
67 views

AC line isolation on multi-level PCB design

Due to space limit I had to design the PCB in multi-level form, the top front side of the PCB is AC line and under that is DC capacitors: Is the 3mm air gap between AC line and DC capacitors enough ...
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1answer
127 views

Isolating 220V AC from low voltage DC on the PCB

Below picture is the rectifier section of design on the PCB: The space between AC and DC voltage is ~2 cm, except at the bottom that I put four M3 holes which I'm going to drill and connect them to ...
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1answer
109 views

Do small 1:1 isolation transformers exist?

I am building a Nixie clock that will be powered from 110V wall power. The design is based around having this 110Vac as the input voltage, but I wanted to put an isolation transformer inline for ...
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2answers
223 views

Switching MOSFET with isolated gate

I am trying to isolate the battery which powers the gate control circuitry from the battery which powers the hight-current load being switched by the MOSFET. Here is the basic circuit configuration: ...
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Relay module and Arduino Isolation; How to acheive?

I'm going to control a 3phase motor with an Arduino Pro mini and and a 1 Ch. relay module. In numerous articles it's been advised to separate Arduino and relay module's Vcc. For sure, the second ...
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38 views

isolation transformer in outdoor case (telecomm)

I need to build an outdoor cabinet to feed my wireless components. I have frequent atmosferic discharges and I thought to install an isolation transformer to reduce spikes from 220volt ac source. ...

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