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Questions tagged [isolation]

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

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28 views

DALI optical isolation of signal, but no power isolation?

The DALI standard suggests a separated power supply, because the DALI control lines are not galvanically isolated, so mains voltage may appear on the lines (and the standard suggests that DALI devices ...
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1answer
46 views

Disabling isolation to reduce noise from EMI

A technician was suggesting we try connecting an isolated ground (described below) to a non-isolated ground suggesting it could reduce EMI noise and possibly fix an issue we're seeing (which we don't ...
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2answers
65 views

I2C bus isolation for dummies

Consider you have two devices designed to be I2C masters in same bus. However, only one of them is operational at a time and the other one is completely powered down. In my case the devices have ...
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1answer
57 views

Is isolation between user accessible circuits and protective earth necessary for safety?

First let me say that I understand that this question is best answered by someone familiar with relevant standards (whatever those may be). Let me give some background. When I'm designing a board at ...
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37 views

Negative feedback optical amplifier

Why the feedback network is necessary in this optical amplifier ? How the circuit would work without the feedback photodiode ?
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1answer
60 views

How can I model/understand this isolation module's CMR rejection ability?

Before asking the question here I have to show how I was demonstrating the CMR simply: The first circuit above represents a 100dB CMRR and the second circuit shows how the 1k Ohm source impedance ...
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2answers
102 views

How isolation is achieved in isolated channel oscilloscopes?

I tried to search something about this but found only a small amount of information. What confuses me is that all isolation amplifiers, optocouplers etc. I could find usually work at much lower ...
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2answers
42 views

Comparing differential-ended and isolation amplifier outputs for an “unbalanced” source input

I tried to simulate the effect of common-mode interference on unbalanced sources for three different inputs: single-ended, differential-ended and isolated. Below I inject a 1V common-mode voltage to ...
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1answer
82 views

Rs-485 isolation

Hi, I have RS485 communication circuit as shown in figure. But it has no isolation, only SM712 is used for ESD protection. Now, i think it will be better to isolate the it.So, how can i isolate it? ...
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1answer
52 views

Isolating a small pin on a flat cable

A motor on my HiFi system (which is supposed to lift a volume controller) has broken. The motor is stuck and I don't want to fix the mechanical part. I assume disassembling the volume controller would ...
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1answer
106 views

Enhancing the bass response of an audio isolation transformer

Below is a simple buffer circuit using an isolation transformer : The green trace is the output of the transformer and the blue trace is the input signal (20hz to 20Khz sine wave). As you can see the ...
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1answer
94 views

Any cheap and easy ways to isolate analog signals?

I want to isolate some transducer signals. Everything I've looked up is pretty expense/requires a lot of supporting circuitry which, because of volume, is not ideal. What is the easiest/cheapest way ...
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29 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 ...
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1answer
44 views

Function of transformer as a filter in isolated DC-DC converters

As far as I understand the isolation is achieved by a transformer(and besides this sometimes also using an optoisolator for the feedback part) in a DC-DC converter. And this is a galvanic isolation.(I ...
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1answer
35 views

Mixed equipment grounding

I have built an analog circuit PCB that I want to debug. It has to get a bipolar power +-5V and an input sinus signal. The signal on the CUT (circuit under test), has buffered inputs (but a common ...
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2answers
238 views

How can I isolate voltage dividers so they aren't interfered with by other parts of the circuit?

I have a small and very basic circuit that PWMs an RGB LED. It has a potentiometer to allow me to set brightness level for night time and a LDR that allows me to detect night time. I took some ...
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3answers
100 views

How to isolate several voltage sources that feed a single voltage meter

I need a way to isolate several voltage sources around a large vehicle that feed a single voltage meter some distance away on a panel. Each source is selected by a momentary-spst (at the source). ...
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0answers
40 views

Is there a range for an isolation transformer's common mode rejection frequency?

Below shows use of an isolation transformer in a system: (taken from this site) At C(right after the isolation transformer) the waveform is cleaner comparing to A and B. What frequency of ...
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2answers
1k views

Protecting two layers of PCB with electric tape?

I have soldered several small PCBs, and I want to stack them together (using hex spacers). However, since lack of (vertical) space it could be that some components (on the top) might touch the wires/...
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1answer
50 views

Electrical isolation in PLC output cards

Every output card spec sheet I read says something about electrical isolation. One I read recently said "Isolated 1500VDC channel to channel". What does isolation mean and what advantages do isolated ...
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0answers
38 views

Preventing the voltage between two isolated grounds from exceeding max rating

Consider the low-side current sensing application shown in Figure 1. Grounds 1 and 2 are galvanically isolated. Assume, for example, ground 1 is the NEUTRAL line on mains power (\$V_g\$), and ground 2 ...
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2answers
49 views

Differential signal isolation

In differential signal circuits (specifically, RS-485), there is usually an isolation between the signal processing / generation stage (eg, microprocessor) and the line driver chip (something like a ...
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0answers
74 views

Isolation for USB 2.0 High Speed (480 Mbps) [duplicate]

The fastest isolators available a a reasonable cost are 150 Mbps per channel. High Speed USB has a data rate of 480 Mbps. So how do you isolate a HS USB? The first thing that comes to mind is to ...
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2answers
40 views

Isolate a digital signal that changes its amplitude

I have to isolate a digital signal that has the following characteristics: frequency: between 1 and 1000 Hz amplitude pk-pk: 12V offset: 0-6V With "offset" I mean the actual voltage may change from ...
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2answers
88 views

What is the purpose of galvanic isolation?

Is it correct to say that the primary reason to have galvanic isolation (ensuring minimum clearance and creepage distance for required voltage of power circuit between HV and LV) between the HV power ...
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2answers
132 views

AGND and DGND connection using flash ADC, totally stumped

So, I am designing a PCB with the classic scenario of having both sensitive analog signals and noisy digital signals... Analog and digital regions are separated. the have their own gnd planes and ...
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2answers
70 views

Isolation Amplifier Gain Problem

I'm having a little trouble with an isolation amplifier. I'm using an HCPL-7800 isolation amplifier, in the circuit format provided by the manufacturer as a test circuit, and feeding it low voltage DC ...
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3answers
56 views

Isolate low power i2c ADC

I'm using the MCP3421 to read voltages from thermocouples on battery power. I would like to get this working over USB but I think the low common-mode range of the ADC could be problem so I am ...
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1answer
40 views

Isolation Amplifier? Reading differential voltage on 600 V lines

I need to measure the voltage across the leads of a thermocouple, the thermocouple being physically connected to a 600 Vdc terminal. The instrument which measures the thermal couple (thermometer) ...
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0answers
41 views

CAN Isolator function

Why is a CAN isolator used? Known background theory: The CAN isolator is used in order to protect against surges / EFT's, reduce the effect of ground loops (common mode EMI) and eliminates voltage ...
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1answer
177 views

Creepage Distance in Altium Designer

I have a design with a high voltage and a low voltage part. Between the two I need to have a creepage distance of 8mm. Some optoisolators I use in my design are not wide enough on the PCB footprint, ...
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1answer
178 views

Controlling a high voltage relay by a PC USB

My 2.1 speaker's transformer is consuming active power even when the PC is off. I know it because it is always warm. Thus, I want that only when my PC is operating the transformer will get the AC ...
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3answers
678 views

RS 485 ground signal and chassis

I have a shielded twisted pair running from one device polling several devices in an RS 485 loop. The conditions: The devices are in parallel as they should be. The termination resistors are in ...
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2answers
97 views

Automotive signal isolation - alternatives to optocouplers

I'm working on an automotive project, where I'd like to interface various digital signals to an MCU. The signals can either be ON/OFF (e.g. radiator fans) or measurements of pulse frequency, width, ...
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4answers
79 views

Proper insulation of wires connecting to the submersible pump (5V)

I'm building a simple plant watering station, which uses a relay-controlled submersible water pump (this one). The intent is to submerge the pump into a large enough water container to avoid frequent ...
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2answers
118 views

How can I split a 5v power supply into 4 isolated (no shared ground or live) channels?

I need to power a number of tp4056's with the battery outputs in series (using tp4056's because I have a bunch already, and because I want to be able to add more cells in series later). If I do this ...
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3answers
832 views

How does Galvanic isolation work?

I am unable to understand how does galvanic isolation work either via an optocoupler or a transformer. In an optocoupler, the input side current caused LED to emit infra red light which basically ...
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1answer
164 views

Insulation Voltage of Aluminum PCB - With and Without Electronic Components

We are working on a product that contains an LED module consists of 66 LEDs (33s x 2p - 100VDC load voltage). We'll use aluminum PCB due to the thermal requirements but the customer requirement ...
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2answers
116 views

What to look for in an isolation transformer?

What do you want from an (isolation) transformer besides it having the minimum voltage/current/power(/frequency?) specs that the to be isolated device needs? Does it matter whether the transformer is ...
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1answer
45 views

Isolating Power in Communicating 5V Sub-systems

I have been plagued by a sensor sub-system which, when connected to my base micro-controller platform, intermittently causes issues that I would categorically associate with power sequencing issues at ...
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2answers
77 views

Current loop protection from wrong connection of the wires

I have built a current loop protection circuit based on the topic Using a microcontroller ADC to measure a 4-20mA sensor It works good. The next step is I want to protect the input of the circuit ...
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0answers
37 views

Increasing isolation in power splitter

I want to use This module\minicircuit Power splitter. I am working on the 2.4GHz to 6GHz band. The isolation parameter on the stated for these frequencies in the "Typical Performance Data" table is in ...
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0answers
41 views

A heat resistant connection between power supply and a resistive wire circuit (heat grid)

I'm wondering about methods to isolate thermically from the power source a resistive wire circuit (main function: to heat things). I'm sure there is a non-DIY solution (i.e. "buying something") which ...
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1answer
55 views

Convert dB to resistance

I am new to this, but I wanted to ask how it would be possible to convert a dB value into resistance. I've been looking at an isolated analog switch from http://www.ti.com/lit/ds/symlink/ts5a3359.pdf ...
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3answers
430 views

Shock from Capacitive Coupling

In an AC supply which is not earth grounded, I see a small amount of current flowing to ground from both wires of the supply (live wire has higher) even though the circuit is incomplete. It is due ...
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0answers
30 views

Isolation of circuitry from heat source

I'm building an electrolysis unit which will comprise a refractory crucible, containing the electrolyte and the electrodes. The heat will be generated from a furnace to aid the desired reaction. A ...
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0answers
80 views

Need a system to isolate an external charge circuit in a vehicle

I am looking for some assistance with options in isolating 2 parts of a circuit. I have a 4G hotspot that I am using in the car, powered via the cigarette lighter socket (rated at 12V/10A) and a 5V ...
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1answer
92 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 ...
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67 views

Designing isolated flyback with multiple outputs

UPDATE: as suggested, I split this question into separate parts (links below). I left the last one here. It is so silly I am rather proud of it ;) UPDATE 2: it seems that breaking one post into ...
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2answers
588 views

Were do ground pins on isolation transformer go [closed]

The outputs from transformer have a ground. Is output ground earth ground? Isn't the whole point for those transformers not to provide earth ground potential? Example: