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Questions tagged [isolation]

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

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2answers
31 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 ...
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1answer
33 views

how to isolate coupled noise source in parasitic capacitance in high voltage pcb design?

I'm new designing a high/medium voltage (V <=10kV) with low voltage and low current (10mA). There will be only a few HV relays. Their coils will be triggered by LV. I have read some literature ...
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3answers
34 views

Voltage isolation at IC pin when Vcc=0V

I recently started a project that utilizes a piezo sensor to sense vibrations. The piezo signal is fed to a uC in order to detect vibrations above a certain threshold. However, the piezo's high ...
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0answers
24 views

Measuring resistance (low-voltage) and shooting high voltage over circuit [closed]

I'm having a source shoot higher voltages 24-60V over a circuit with 2 contact points (poles). With an arduino (3.3V) (other voltage supply, other circuit) I want to constantly/permanently measure ...
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0answers
40 views

Isolated Voltage Measurement

In my application I need to measure a voltage that is in the area of 50V, but my microcontroller has to be isolated from my power circuit. I came across the ACPL-C87A-000E IC. I followed the typical ...
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2answers
60 views

Optocoupler isolation necessary?

The circuit diagram below shows two possible options for a circuit: simulate this circuit – Schematic created using CircuitLab The difference between both circuits is the use of the ...
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0answers
53 views

SPI Isolation : What is the point of the ADuM3151 etc

I was looking at ADI's isolators designed and marketed for SPI, such as the ADuM3151. I'm interested to know what makes these isolators special, in that what the point of them is. The isolators don't ...
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0answers
14 views

Isolation of SD IO pins during off state

I have a project at the moment that uses a PMOSFET to switch the supply to an SD card. According to the SanDisk SD datasheet available here: Because there are clamping diodes on the CMD, CLK, and ...
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1answer
39 views

How to tell if the switch is open or closed on a mains line?

Imagine a circuit that may or may not be connected to mains voltage. If mains is connected, it is trivial to determine if the switch is closed, by using a zero-cross detector circuit. If mains is ...
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1answer
49 views

Monitoring open/closed-circuit on a mains line

I am building a custom refrigerator control circuit. The refrigerator is solely powered from a battery source, using an inverter. For power savings, the inverter should be off when the motor is not ...
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2answers
67 views

Do the photocouplers on this module have any possible purpose? [duplicate]

I purchased a number of these relay module boards off AliExpress. They consist of the following 16x relays, 12 volt coils A LM2596 setup as a buck converter 2x ULN2803A darlington arrays 16x 817C ...
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1answer
74 views

What can be the reason multi-meter shows continuity even though there is isolation?

I'm dealing with a module where the block diagram is given as follows: The datasheet can be found both at here and an alternative one here. When I perform a continuity test with a multi-meter ...
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1answer
45 views

Is there a problem connecting PSU grounds to earth for an isolated signal chain in this scenario?

For a precision and simultaneous analog signal data acquisition; several force, temperature and acceleration transducer outputs are coupled to a daq board input channels through signal conditioning ...
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4answers
3k views

Interfacing a button to a microcontroller (and PC) with a 50 m long cable

I am designing a board that will be plugged into a computer and will read the status of a button ~50 m away in an office environment (it's actually a lot closer, but the cable is long). I think ...
0
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1answer
62 views

Full wave rectification with only an antenna input?

I am designing a receiving circuit and would like to do a full wave rectification of a sine wave signal received from an antenna. My problem is figuring out how to isolate the two ground signals of ...
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2answers
53 views

Isolating main power traces on backside of the PCB

I am currently making a build-in PSU for my own audio-effect-rack-thing. The internal PSU consists of two print-transformers(THT), one for 6VAC and the second one for 9VAC. These are also pretty low ...
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0answers
58 views

Whats the best type of connector for test equipment? [closed]

I am selecting the components to use for a tester I am developing. I am looking at various types of board to board connectors. The requirements are: Rated to least 2A. Rated to ~200v. *High ...
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1answer
95 views

Transformer Insulation - High Voltage can Jump Through Ferrite Core?

First of all, I really searched the topic on both EE.SE and Internet but could find nothing. If this is asked before, please forgive me. As I stated here earlier, I was working on an HV amplifier. ...
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0answers
26 views

Automotive 12V Analog and Digital input coupling and isolation

There are numerous questions on SE about classical automotive signal adaptation to microcontrollers. The circuit below uses a few common techniques for analog signal interfacing when a ...
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1answer
95 views

Does CANbus need to be isolated?

In my design - rugged computer - I have connected the digital gnd to the isolated CANbus gnd by mistake. Does the CANbus standard state that it has to be isolated? Can that connection harm the CANbus?...
1
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1answer
49 views

How do some instrumentation amplifiers handle such wide common-mode input voltages?

In a previous question, I asked about the detailed construction of in-amps. Now, I'm curious about a feature that some of them have that I'd like to know how they achieve: I used an INA286 in a ...
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2answers
89 views

Analog Isolation Question

There appears to be several options out there when it comes to isolating analog signals. This topic has been addressed on this website in a few forums as well. The problem for someone such as myself....
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1answer
47 views

What is the purpose of a schottky/zener couple on an isolated flyback topology?

This isolated flyback topology has been generated by TI's webench. It's a classic schematics with a feedback going through an optoisolator. There are, however, two diodes connecting the switching ...
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0answers
55 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
57 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
90 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
68 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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0answers
38 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
71 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
105 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
46 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
112 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
54 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
142 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
203 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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0answers
55 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
57 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
39 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
292 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 ...
2
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3answers
106 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
50 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
63 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
42 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
73 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
101 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
42 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
108 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
201 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
101 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 ...