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Questions tagged [isolation]

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

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31 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
205 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
89 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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31 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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44 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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36 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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44 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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25 views

VITA 46.0 VPX grounds isolation requirement

VITA 46.0 VPX standard demands: Rule 3-15: Plug-in modules shall provide a minimum dielectric withstanding voltage of 500VDC +/-10V and a minimum resistance of 1 megaohm between safety ground and ...
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43 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
37 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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100 views

Balanced speaker level to unbalanced line level

I am attempting to take a balanced audio signal at speaker level (~10V peak to peak) and connect it to an unbalanced 3.5mm jack at line level. I found this schematic which suggests using a transformer ...
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2answers
82 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
78 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
56 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
50 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
37 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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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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72 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
99 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
552 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
76 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
73 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
88 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
731 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
147 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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76 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
66 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
31 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
39 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
50 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
341 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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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
63 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
79 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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66 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
308 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:
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4answers
47 views

Isolation with inverter

Say I used a 12v car inverter powered by a 12v brick connected to ac mains (no ground pin) to isolate a scope and bench dmm, the inverter has no earth ground. Is the equipment isolated? Is lack of ...
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2answers
282 views

Cheap isolated mains current measurement

I'm looking for cheaper ways to measure current in a load switched by optoisolated TRIACs, without losing galvanic isolation (no breakdown below a couple kV) between the microcontroller and the load. ...
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1answer
46 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 ...
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118 views

how necessary is an isolated DC/DC for an ESP32-wroom-32 digital circuit in an automotive 12/24v System?

I want to use an ESP32-wroom-32 into an 12/24[v] vehicle. To eliminate ground loops and separate the digital circuit. In my first circuit, I use an Arduino, an LM2596 step-down module, and ltv-826s ...
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2answers
177 views

floating ground

For a big machine (rope shovel) we put a custom electronics board (gps) in an enclosure. It is connected to the cabinet with Power over ethernet (POE). The POE switch is connected to an isolated power ...
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2answers
77 views

what is the meaning of isolation of transformer between i/p to o/p is 1 kv & mains supply to body/chassis is 2 kv

I have to design a transformer with isolation factor as follows:- Isolation between i/p & o/p is 1Kv Isolation between mains supply to chassis is 2.5Kv How to calculate these isolation factors ...
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1answer
35 views

Isolation of voltmeter via DC->AC->DC conversion

I bought a combination ammeter/voltmeter which has the restriction that the measurement/display circuitry must be powered from a different source than the measured voltage. What is the underlying ...
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2answers
135 views

Safety: Mains step down transformer vs SMPS for bench power supply?

Between a mains step down transformer and a SMPS, which would be safer for a bench power supply? I cannot look inside the transformer in either case to judge the insulation quality. But, if the ...
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1answer
50 views

Dual battery setup

I want to make a dual battery setup on my car. Doing some research I came across the two main techniques to do this, both based on isolate the two batteries being fed from same alternator to avoid ...
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1answer
36 views

Do I need different isolations among long-wire switches?

I'm playing with an MCU board (like Arudino) to read the state of several switches in my home (i.e. magnetic switches). The wires between the sensor and the board are quite long: 15+ meters in a star ...
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1answer
78 views

galvanic isolation for lm555

Hi guys I am trying to implement galvanic isolation for my lm555 square wave generator. I am designing a marx generator so this is essential. I am new with transformers, at the moment all I want to ...
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3answers
339 views

Is galvanic isolation needed when the output voltage is higher than mains?

For a flyback converter, 120 V AC in and 400 V - 2000 V out, is it necessary to provide galvanic isolation between the input and output? First, from a safety point, would not having a direct ...