Questions tagged [isolation]

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

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2 answers
471 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 ...
0 votes
2 answers
80 views

How is my isolation transformer not short circuited?

I received a 3 phase 240 to 208 isolation transformer, and I am unsure how the current configuration (as it was shipped to me) would not cause a short circuit. When I do an ohms reading on the high ...
1 vote
1 answer
284 views

Cascading Isolated Power Supply

I want to implement a few chips for battery management and due to the ADCs of each cell working at bigger voltages each, and each chip (I have to cascade three ICs LTC6803-4) with a maximum voltage ...
2 votes
1 answer
122 views

PoE: PSE isolation requirements

On the robot I'm currently designing, there will be several connectors with PoE ethernet and supply voltage (0 V, 24 V) and some other signals (referenced to 0 V). I'm unsure if I need isolation for ...
1 vote
3 answers
156 views

In aircraft power supply, why is the neutral not connected to chassis GND unlike household utility power?

Usually the chassis of any household equipment is connected to earth ground for safety. Part of the culprit is neutral being connected to Earth ground. (Reasons are mentioned in this post.) My ...
0 votes
1 answer
42 views

Floating output voltage in USB chargers?

A USB charger is usually galvanically isolated from mains for safety reasons. If I touch the output connector while standing on the ground (i am at earth potential), will I get a shock? I think yes, ...
1 vote
2 answers
42 views

Isolate battery from a charging circuit... to use a stronger charger

I have an inverter that currently uses a single 7 Ah lead acid battery. While the rating of the inverter is sufficient to my purpose, the battery does not provide nearly enough run time, and being ...
0 votes
1 answer
411 views

WS2812/15 opto-isolated with 6N137 and MOSFET?

The goal I want to isolate a 3.3 V MCU (ESP32 C3) from a WS2815-Strip but I had no luck so far. I already read these threads, because I think they're dealing with a similar problem: MOSFET - 800 kHz ...
0 votes
0 answers
11 views

IEC61010 applicability for non-measurement category rated circuit?

I have measurement circuit that will be rated for CAT II 300V but do allow input voltage of over 300V up to 1kV. In IEC61010 6.7.3, "Insulation for secondary circuit derived from main circuits of ...
7 votes
2 answers
3k views

DC/DC isolated supplies in series for higher voltage?

Can I chain two isolated DC/DC supplies together for a higher output voltage? (Say, a 48V and a 12V to get 60V?) They'd be fed from the same 24V DC source. I've asked a related question before (...
0 votes
3 answers
321 views

How to isolate audio signals from each other using op-amps with the same single supply?

Reuploaded corrected picture, as the old one was with confusing ground connections: I am new here, so please be patient if I'm doing something wrong. I really need some help as I can't figure it out ...
0 votes
1 answer
249 views

synchronise many microcontrollers

In my project I'll use modbus protocol for serial communication over RS485. There are more than 320 slaves which separated equally in 2 groups. Every 16 slaves are powered from the same supply and ...
0 votes
0 answers
53 views

Why are USB galvanic/isolators needed on battery operated devices?

Why are galvanic/optical USB isolators used? I am an astro-photographer who does imaging at remote site locations on battery. I never encountered galvanic/optical USB isolation in devices until ...
0 votes
1 answer
43 views

Half-bridge driver ground loop elimination

I built this half-bridge driver using a generic Schmitt trigger/hex inverter IC and a 555 timer as the square wave generator. By varying the value of the resistors, the dead time can be adjusted and ...
3 votes
2 answers
462 views

Grounding balanced secondary isolation transformer for EMI suppression

simulate this circuit – Schematic created using CircuitLab Which is the best secondary connection to clean the main line power from EMI, line noise and HF harmonics by using an isolation 1:1 ...
2 votes
1 answer
245 views

Isolated circuits: can their reference voltages (GNDs) be at the same potential?

Suppose there are two independent circuits isolated from each other. If they are isolated, the impedance is very high between them (ideally infinite) and there is no current flowing from one to the ...
4 votes
1 answer
336 views

Can a FELV circuit be connected to a SELV circuit?

This might be a very very simple question, but I'm unsure how to interpret the rules. I have a circuit which switches 230V using relays. The circuit is a motor controller for a motor control box ...
2 votes
1 answer
259 views

Isolation between measuring voltage from low current circuit?

simulate this circuit – Schematic created using CircuitLab I have a low current current circuit and I would like to be able to measure the voltage on one point of the circuit but have ...
1 vote
2 answers
366 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 ...
1 vote
4 answers
696 views

Isolating DC from DMX signal

I have a DMX controller using a 3-pin connector (gnd, data+ and data-). I need to connect it to some cheap chinese DMX lights. The problem is that the lights are powered over the same 3 lines using a ...
18 votes
4 answers
13k views

Cellphone charger has no transformer?

I opened up a really tiny mobile phone charger I have, to see how it is designed. The entire "charger" is integrated into a small 2-pin mains plug, 1 x 1.25 x 0.5 inch, that has an USB socket for the ...
0 votes
0 answers
26 views

Read voltage (isolated circuit) from 24S Li-ion battery pack and output 0-5 V signal

I am finishing up a EV-conversion and everything works well except the SoC display. The BMS I am using outputs 0-5 V to indicate the SoC but the output pin for this signal is broken from the previous ...
0 votes
1 answer
279 views

Detecting a connection to protective earth from an isolated circuit

I recently built a unisolder soldering station. One of its features is a sleep mode based on whether or not the soldering iron handle is present in its holder. A SLEEP pin is provided that's weakly ...
0 votes
2 answers
315 views

How to make a smart precharge circuit

I want to build a circuit that monitors the voltage at either end of the precharge resistor circuit. Since the load will have capacitance, I should expect an RC time constant curve on the load of the ...
1 vote
1 answer
129 views

RS232 : dedicated signal ground or common with power ground?

I'm designing the PCB for a robot, where I plan to add some connectors for external RS232 tools (provided by the client). Each connector will provide power (either 24 or 48V, at 5A max) and an RS232 ...
0 votes
3 answers
86 views

Eliminating Noise from Audio Amp Board Input

I made this project by shajeeb (linked below), and I am having trouble with noisy ground lines. The circuit I made is the same as the diagram below except for where I connect the speaker and amplifier ...
1 vote
0 answers
3k views

How to interface a Raspberry Pi Pico to DMX / RDM

Years ago, I was looking at creating a stage DMX controller using AVR. Time moved on and the Raspberry Pi Pico has now been released. I'd like to revisit the project using a Raspberry Pi Pico, which ...
0 votes
2 answers
53 views

Isolating USB3 with an ADUM4160

I've not played with USB much besides the ordinary FTDI UART bridges. Recently, I have reason to use an FT601 with a USB3 port configured for super-speed operation. As this is connected to a fairly ...
3 votes
2 answers
3k views

Secondary car battery voltage

I have an accessory battery for powering devices when the vehicle is off. The Secondary battery is connected through a battery isolator. Each battery is separately connected to chassis ground. When ...
0 votes
0 answers
67 views

Driving Gate from MCU (using 6N136 and TC4431)

This is my first time trying to use this optocoupler (6N136) I'm trying to control a MOSFET gate with the least switching delays (rise and fall timings) possible, while making the MCU isolated from ...
1 vote
0 answers
55 views

Reducing Isolation Transformer Leakage

I watched this video and wonder if its complete separation of primary and secondary coils is the normal way to wind a low-power isolation transformer (e.g., 60Hz 120V 120VA). I particularly want low ...
0 votes
0 answers
49 views

Using a non-isolated DC power source for a microcontroller

I am designing a frequency converter for an approximately 200W three-phase motor operating at 220VAC. I intend to use a microcontroller for control and measurements. To cut costs, I am considering ...
2 votes
1 answer
123 views

Isolated flybacks in series to generate high-voltage [closed]

I'm considering placing isolated flyback converters secondaries in series such as the image below. I want to drive the transformers individually using synced clocks (such each transformer has its own ...
0 votes
1 answer
157 views

MCU signal isolated and Amplified (Optocoupler+BJT+Mosfet)

I've com up with the following design. I feel I've used too many components, don't know. but I have some reasons for anything included in the design. PULSE_A : some low frequency (50~1000Hz) low duty ...
0 votes
1 answer
676 views

Designing flyback converter - multiple isolated outputs

Can I treat 2 secondary coils with dual voltage output as one with double voltage for the purpose of calculations? This seems to be OK for all formulas based on output power as technically the ...
1 vote
1 answer
50 views

Wurth transformer secondary pins on left and right side of transformer

I am looking to use Wurth Transformer 750310988 and I have noticed its pinout is very bizarre. My application is I want to float the secondary of this transformer up to 500VDC and provide a isolated ...
2 votes
3 answers
348 views

Isolation transformers and short circuits

For some quick background and info: I'm a relatively fresh (~2y/ experience) EE in the solar field. I work in the R&D department of my company. My country operates in a 230/400V 50Hz grid. We are ...
0 votes
3 answers
175 views

Understanding RS422 and choosing drivers

I want to communicate 2 MCUs using RS422. I need to have some isolation, so the driver should have 3.3V side and 5V side, isolated. All I can find in the market are half-duplex drivers, I understand ...
1 vote
2 answers
434 views

Galvanic isolation in automotive environment

I am using a linear regulator (MIC29302WU) to power a computer mounted inside my car. There is significant noise being passed along the ground of the regulator to the main computer. I verified this by ...
4 votes
0 answers
62 views

Mixed pollution degree creepage distance

Say you need to comply with a creepage distance but you can't do it under a specific pollution degree. I had 2 scenarios where I had mixed pollution degrees: The creepage distance is almost enough ...
1 vote
2 answers
149 views

How can we safely test a mains powered device?

We have small non-isolated 230VAC devices that transform mains to LEDs running at 32V, 20mA. The lights are directly connected to live, neutral and earth like a standard lightbulb would be. Since ...
1 vote
2 answers
413 views

Preventing shock risk on isolated transformer secondary circuit

I fully understand that you cannot get a shock from either phase1 or phase 2 on the secondary of the isolated transformer, however you can be shocked by touching both. My question is how do you ...
2 votes
0 answers
47 views

Ground isolation in multichannel mixed-signal systems

There are some similar questions to mine but I have a few more specifications on top of them. Therefore, I am not 100% sure whether to ask as an iteration or present my own question on a clean slate. ...
0 votes
1 answer
358 views

Combining ECG and EDA (skin conductance) in the same chest electrodes. Possible and how could it be done?

Currently I'm designing a wearable, battery powered module that combines several sensors into a single device. In this device are modules for both ECG measurement (heart beat) and EDA (skin ...
4 votes
2 answers
135 views

Isolation Topology in SMPS

I have been researching SMPS designs as a hobby recently and finally have the courage to build one for theoretical and practical understanding. I have chosen an isolated design looking at several ...
4 votes
9 answers
2k views

What options exist for isolating a high power DC analog signal? [closed]

I have a high power DC signal that can range from 0-325 VDC. The source is capable of delivering up to around 150 amperes at 325 volts. I need to monitor the voltage as an analog signal by reading it ...
0 votes
1 answer
257 views

Why did the Arduino burn in this circuit?

I've designed a PID fan control system which takes air quality measurements via sensors and sets the AC fan motor speed by changing the H bridge frequency. Circuit is as below: Full: Top: Bottom: ...
0 votes
0 answers
60 views

What is wrong with my double pulse test Ltspice schematic? Gate pulse is not getting generated when I connect the gate driver for 800V application

What is wrong with my double pulse test LTspice schematic? Gate pulse is not getting generated when I connect the gate driver for 800V application. Any connection error?
1 vote
2 answers
153 views

What does 2xMOPP really mean

I am a student and I am designing a medical device that has a type CF applied part. I know the specifications that the applied part must comply (4kV of insulation, 8mm of creepage, <10μA patient ...
1 vote
1 answer
73 views

Isolate current flow in Ltspice using switch

I am trying to control the flow of current by the switch SW, I have used an independent current source I. However the switch is ineffective to isolate the resistor R1, because the switch is basically ...

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