Questions tagged [isolation]

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

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Beginner Electronics Hobbyist Q re: oscilloscopes and grounding

I'm in my infancy as regards electronics, but will soon be acquiring an O-scope as part of my learning plan. I'm at the stage (and will be for some time) where I'm building simple things on a ...
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1 vote
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Connecting the grounds on a non-isolated DC/DC converter

For isolated DC/DC converters, I know that it's a good idea to have two different grounds on both sides and that we should avoid to connect the two grounds together as the isolation is useless when ...
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Looking for a good text book describing active clamp forward converter

Can anyone refer a standard text book for understanding Active-clamp forward converter in detail? I could only find application notes and datasheets on this till now. I have gone through below books- ...
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How to use plane layers with Altium and Eurocircuits?

I don't quite understand Plane layers in Altium. For one particular project, we made a decision to use Plane layers instead of signal layers. When exporting the production files (Gerbers) and ...
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Isolating RF Ground is it wise?

I am designing a GPS module and I am planning to isolate the RF GND from the DC power supply GND with an inductor. I have chosen the Murata LQW18CN4N9D0ZD because the low inductance will have low Ldi/...
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6 votes
2 answers
1k views

Why is the telecom input power supply range 36 to 72 V (polarity ignored)?

Why is the telecom power supply voltage level specifieded with a wide range: 36 to 72 V? Is it because the rectified AC voltage would have variations as per AC line variations? We could easily get a ...
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  • 2,051
1 vote
2 answers
116 views

Why do 1:1 DC/DC isolation transformers have different inductance values?

I am new to power supply design. I need to design an isolated, unregulated DC/DC power supply, 28VDC, 45W. The purpose of this circuit is just to provide isolation with 1:1 voltage and power. As I was ...
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Would this isolated AC peak voltage detection circuit work?

I have adapted the circuit from Michael's circuit in Efficient method for isolated detection of AC voltage without a stepdown transformer to detect on either side of the positive half-cycle peaks, ...
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Problem connecting two DC-DC converters in one circuit

I'm building an audio mixer for microphones, and have a problem with the power supply part. I'm designing this board to work with several voltages which are +/-15V, 5V, and 48V (for phantom power). I ...
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2 votes
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39 views

In a forward converter, why do we need a separate controller for secondary side switches?

LT8311 IC is said to be a synchronous controller IC for a forward controller. Why do we need a separate controller at secondary side as the PWM pulses of primary side should dictate the synchronous ...
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  • 2,051
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protect from in rush current of buck convertor

I made a PCB base on the following schematic, it uses a buck convertor for 12 to 5 v and then uses an LDO for 5 to 3.3 to run my ESP module I use 2 P-channel MOSFET for polarity protection , but ...
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Why does Japan use 100V AC as opposed to 120 or 230V, and why are many of their plugs ungrounded?

I don't live in Japan but I have noticed this interesting phenomenon when it comes to their electronics. I'm buying a PC-9800 and because it remained isolated in Japan its power supply is only rated ...
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Best option for isolation of output voltage from controller board?

So I have the following schematic: I have a 400V output voltage which I have stepped down to less than 10V using resistor dividers in order to measure via DSPACE 1104 board(https://www.dspace.com/en/...
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-1 votes
1 answer
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Isolation high side MOSFET

I have high side MOSFET component VN7003ALH, with the following information, it has an input pin instead of a gate. As the electrical specification shows, the MOSFET drain and source voltage adjust ...
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Isolation voltage to distance conversion

Introduction: I am designing a board with a standard IEEE 802.3 1000Base-T ethernet interface. The board is a standard 4-layer FR4 board with all components on top and GND on Layer 2. The IEEE 802.3 ...
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Single vs two pole breakers - Single phase loads on IT power with distributed neutral

Are two-pole breakers required on single-phase 230 V loads when connected to a 3-phase supply with IT earthing system (with distributed neutral) in Germany? Where in the standards is this requirement ...
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Isolate power supply with a HX1188NL

I need to isolate a 24V DC power supply using the HX1188NL component. How can I connect the ground to the two sides of the transformer? Do I have to short the centre sockets with the negative pin?
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Smallest lowest cost way to isolate RGMII signals between devices on the same CCA?

I have a single Gigabit Ethernet line coming out of a circuit card. Access to the line will be shared by two CPUs. To facilitate shared access, the CCA will have an Ethernet switch IC. The switch IC ...
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1 vote
1 answer
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Two-ground issue

I've been working on a project which I need to rectify, filter and later lower the input filtered voltage (311V) to 12V, as shown in the picture making use of a flyback converter. The problem arises ...
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2 votes
1 answer
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PCB layers as isolation

What voltage can I expect primitive PCB (2 copper layers, one on each side), to hold between one and another layer? I assume removing copper at edges should make the edge path longer, so I am mostly ...
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Bias supply of forward converter: Startup circuitry component selection

The bias circuitry of a forward converter is shown below. Iam unable to follow the derivation of start up resistor values( Rstart) given in datasheet: As per me, \begin{equation} R_{start} < \...
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  • 2,051
1 vote
1 answer
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Difference between Working Voltage and Isolation Voltage?

I am building a board to collect data from a 2000V system. The board is going to be powered from a USB port on a laptop and data collected directly into the laptop. I am looking at Isolated 5Vto5V ...
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What is the meaning of converter operating point statement from the textbook "Fundamentals of Power Electronics" by Erickson?

"Isolated converters with large variations in operating point tend to utilize their power devices more poorly than non-isolated converters which function at a single operating point". What ...
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  • 2,051
3 votes
2 answers
188 views

How do we appropriately select the duty cycle in a flyback converter?

In a flyback converter, we have the freedom to choose appropriate duty cycle by adjusting the turn ratio to meet the desired output voltage. The link says Developers will need to know several key ...
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  • 2,051
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Isolating I2C device behind a switch

I have a piece of closed hardware (proprietary) that has one I2C port. On this port I have two devices, one that requires constant 5 V for counting and the other is a temperature/humidity sensor (also ...
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1 vote
2 answers
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How do certain oscilloscopes have high isolation between channels? [duplicate]

At first, I couldn't think of any mechanism to get great isolation between the front-end and the sense amps because hundreds of volts of isolation sounds like capacitive isolation. Capacitive coupling ...
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4 votes
5 answers
884 views

Can an op amp Vin+ and Vin- be outside the supply voltage so long as their difference is inside it?

An op amp amplifies the difference between signals on Vin+ and Vin-. If I wanted to sample the differential voltage of a pair of signals whose common mode is outside and potentially significantly ...
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2 votes
1 answer
206 views

TMC2209 why are separate motor and logic voltages needed?

Why do motor drivers require separate motor voltage and logic voltage? I am looking to use a TM2209 stepper motor driver. Below is a schematic of how I intend to power it. I'll also be using a MCU, ...
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Isolated UART communication with optocouplers

I want to create a universal PCB for projects requiring galvanic isolation. I'm not in need of fast baud rates, 9600 should suffice. My most common use will be with Arduino 5V/3V3. I want to ask if ...
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5 votes
2 answers
224 views

Creepage for printed boards / printed wiring material and IEC 60664

In IEC 60664-1:2021 table F.5 (former F.4): Creepage distances to avoid failure due to tracking or 60950-1:2005 Table 2N – Minimum creepage distances the second and third columns are applicable for &...
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1 vote
1 answer
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Optocoupler relay, one power source for both relay and microcontroller

I'm having a project, there will be a 16 relays (Lights), which are controlled by 16 buttons. I'm using esp32 as Micro-controller. For achieving this, I've used two mcp23017 boards as GPIO extenders. ...
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2 answers
63 views

Isolated Switch

I have three question on designing Isolated switch (Protected Microcontroller and from accidentally inserting power) Does it matter which side is the switch - on 15V(Isolated side) (image 1) side or ...
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2 answers
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Why does increasing torque on DC motor in circuit affect the speed and functioning of another DC motor in the circuit?

I am working on a project in which there are system components listed below as module: 8 ultrasonic sensors 12-30 V (Sensor module) 3 DC motors (Drive module) 35 V to 5 V buck converter and a 35 V - ...
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1 vote
3 answers
132 views

Purpose of galvanic isolation with one power supply

I searched the forum for similar threads and didn't find the right answer. Why should I use galvanic isolation in a system that contains only one power supply (a battery)? I don't have the right ...
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146 views

Multiple grounds errata corrige?

simulate this circuit – Schematic created using CircuitLab Here is a thought (hopefully) to my grounding/shorting problem (Multiple ground). Would this circuit work being fed by the li-ion cells ...
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2 votes
0 answers
60 views

Isolating low-current, low-voltage digital signals

I'm working with a battery-powered sensor that allows reading its measurements using two digital signals - a clock and a data line. The clock speed is abount 3kHz. In addition to those two signals, ...
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2 answers
48 views

Changing the polarity of the transformer on DUT cause voltage offset on DC measurement with insulating amplifier

DUT (device under test) is powered by 230 VAC and for safety we use additional external 230 VAC - 230 VAC transformer (DUT also has its own transformer for buck converting). We are measuring DC ...
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Measuring voltage on different ground reference – PV

I have a small solar power installation and I want to monitor all the data from it. My only problem left is that the solar panel input doesn't have common ground with batteries (or atleast there isn't ...
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2 answers
54 views

Isolation Transformer Lights-Up Tester Screwdriver

I have an isolation transformer (230V/230V @ 1kVA) and out of curiosity I wanted to see if the lamp of a tester screwdriver would light up. My intuition said that since the secondary of the ...
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2 votes
2 answers
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Measure battery voltage from a device that powers up/down periodically [duplicate]

I have a MCU that powers up periodically to log some data and then powers down (full power off -- not sleep). When powered on, it runs off a battery and I want to connect the battery to an analog pin ...
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How to isolate both Vcc and gnd?

There are three designs of complementary switches, which means that when the button is closed only one of configurations conducts the current and activates the circuit and the other circuit will ...
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2 answers
121 views

Isolated voltage measurement with an ACS37800

I am measuring 250VAC with an ACS37800. It happens to be a PWM based output of a TRIAC. For testing purposes, I am varying the duty cycle and input voltage to validate the measurement circuitry. My ...
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4 votes
2 answers
563 views

Preventing oscilloscope magic smoke by inverter vs isolation transformer? Good idea or not? [duplicate]

There was another question that said that an isolation transformer had to be used to prevent possible damage to an oscilloscope, and I suggested this as a solution, but never got an answer. This ...
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galvanic isolation in high voltage applications

consider a high voltage transformer outputing 100 to 200 kilovolt to a load, both in some oil container. the voltage needs to be regulated through a high ratio divider feedback path. the whole system ...
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High Side, High Voltage Shunt Measurement with Differential ADC

I need to measure the high-side current out of an LED driver. The problem is that the output voltage can be as high as 250V. One solution would be to float an ADC and digital isolator just below ...
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Must a 12V to 110V switched-capacitor inverter output be isolated? if so, does anything special have to be done?

I have an LTSpice simulation of a small switched-capacitor boost converter producing about 12W x 110V of DC, and I was wondering, does it have to be isolated (and need anything special to attain ...
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1 vote
1 answer
81 views

Protect PCB from RF reflection

I am designing a system on megahertz frequency bands (~ 400-1000MHz.) This device is connected to a variable antenna which does not necessarily stay in match with the circuit so there will be some ...
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12 votes
3 answers
2k views

What is this white trace on this PCB?

I saw this image where the "white trace" is (I think) trying to separate high current 220VAC. Do you know what is that white paint made of? EDIT: Image source: Shelly Facebook Page While ...
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5 votes
3 answers
2k views

Safest way to ground a metal enclosure

I am currently building a nixie clock with some high frequency components (GPS) and I am planning on putting the clock in a metal enclosure. The highest voltage used in the clock is approximately ...
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1 answer
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WiFi (2,4G) Antenna Isolation. Why 3 capcitors version does not work

I need to isolate the antenna from the WiFi transmitter. There are some solutions on the market but none suitable for my application. So I have started some experiments. 2x PCBs creating DIY ...
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