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

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1answer
27 views

dual pH sensor system

I am working on the development of a dual pH and dual Pt100 sensor interface for a fish farm tank control system. The tank is expected to have about 75m3 of water, a number of pumps, and feeding ...
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1answer
28 views

audio mixer - is ground isolation needed for each channel?

In every audio mixer schematic that I have found, the signal circuit is described extensively. Here are a few examples: However, these diagrams do not show any considerations for the ground ...
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0answers
15 views

Simulated analog narrow band output ground loop

I am using a Wide Band Lambda controller with a simulated analog narrow band output, the controller system must be grounded to the chassis and is also shared with analog common which connects to the ...
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2answers
118 views

Does this circuit have proper isolation?

I have a development board from Microchip. It works on 12 V DC. The input pins can only work on 3.3 V so what I have done is I have designed a circuit using a PC817 optocoupler. So on the LED side I ...
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1answer
57 views

Varistors set to ground or case by isolated ground/case

I have a isolated ground from the case in my device. The Supply Voltage is +24VDC with Ground and separated CASE, so no safety issues. On any signals coming from the case (Plugs) I put varistors, but ...
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1answer
108 views

Cheap and small alternative to optoisolators: is there any?

Typical opto has several kV isolation voltage (which is not always needed), has relatively big cases (TLP291 in 4-SOIC is one of the smallest as I know) and typical price up to 1 USD in small amounts (...
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44 views

tingly feeling when moving finger [duplicate]

while charging my Ipod or other USB based devices from a wall wart, i get a weird feeling, only when i move my finger against the metal surface. for example, the metal back panel of the ipod. Am sure ...
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1answer
43 views

DC Adapter - AC Potential to Earth

With a switching DC wall adapter, when I measure AC rms voltage from either of the output wires to earth ground, what am I actually measuring and is this a controllable spec of a wall adapter? I am ...
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1answer
26 views

Multi channel isolated barrier: how to tell if inputs are isolated from each other?

I've been trying to figure out if in multi-channel isolated barriers the inputs are isolated from each other. For instance consider the following 2 channel isolated loop repeater: http://files....
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1answer
60 views

Connection between MDB Peripheral and Arduino

I'm working on making a custom vending machine controller using an Arduino as the master. The bill acceptor I'm using implements the MDB communication protocal, which is (I think) a variant of RS-485. ...
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2answers
48 views

Am I able to make a comparator on optocoupler?

Initially I'm trying to make over current protection scheme. So if the R2 current (and therefore R2 + D1 voltage) will go higher than some certain level I should have a signal to break the circuit. I'...
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0answers
17 views

ACPL-C79B problem

This is my first post on this forum. I have a problem with an isolation amplifier and i hope there's someone here who can help me out. Let me explain my situation. I use an ACPL-C79B from Avago to ...
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2answers
101 views

Isolated 1-10V (or 0-10V) output

I need to control an LED driver with analog 0(1)-10V control input. This control device should be very cheap and compact so until now I made a schematic which uses the fact that those drivers have ...
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4answers
218 views

How is galvanic isolation established in an SMPS?

I can understand how an isolation transformer can establish isolation; but since SOME SMPS supplies dont have transformers and they have rectifiers instead; I wonder how the AC and DC ends are ...
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1answer
47 views

Controlling multiple inputs without a common ground using semiconductors

I have a processor with GPIO outputs. It uses 3.3v logic outputs which share a common ground. (In particular, it has internal pull-up resistors, but I could turn on open collector mode) A device I ...
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1answer
78 views

Can a slave i2c IC prevent the master from pulling the the signal low?

I have an MSP430F6659 connected to a ISO1541 via I2C with 1.5K pull-ups. The I2C bus is through wire instead of PCB trace so I'm able to swap out identical PCBs with the ISO1541 ICs. One of these ...
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2answers
44 views

High Voltage to Low Voltage Attenuating Isolation

So for an Electric car team I am on, we need isolation between all high voltage and low voltage components. That being said, for the low voltage side, we need to take the battery pack voltage (0V to ...
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2answers
92 views

Isolated AC/DC Buck Converter

Why are there no isolated AC/DC buck converters around? For applications < 10W (say 5V/1A output) and mains input (85 - 264VC), is it feasible to use a standard buck circuit but add a 1:1 ...
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2answers
49 views

Checking an isolation amplififer

Above is represents an isolation amplifier: http://www.prelectronics.com/pdf/2284-2358-US.pdf The input comes from a DAQ and output will go to a motor. An isolation amplifier is used as in my ...
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2answers
217 views

In an isolated SMPS feedback design, how could optocoupler latency be higher than the switching period?

I often see this in practical SMPS designs. An optocoupler & voltage reference pair is used for informing the controller section about the output voltage level. However, when I read the datasheet ...
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1answer
43 views

Requirements on dielectric strength and isolation between the conductors in an Ethernet transmission line with PoE

I am trying to find out what the requirements are on dielectric strength and isolation between the conductors in a Gigabit Ethernet transmission line. A first place to look would of course be the TIA-...
4
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1answer
238 views

How do I choose an optocoupler for (19200 baud) serial communication between Arduino and RS422 transceiver?

I wish to read data from a Fronius solar inverter via the Fronius RS-422 Com Card option (part# 4,240,001). 1000 meter cabling length The Fronius communication uses a 5-wire RS 422 interface (`RX-`, ...
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1answer
227 views

How to provide an isolated ground for Arduino?

I am designing an EEG circuit at home using an Arduino. Now, the circuit calls for the use of a battery and an optocoupler-isolated ground for safety reasons. I am planning to use Fairchild ...
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3answers
560 views

Why does a UPS need an isolation transformer?

Why would we need isolation transformers before and/or after for a UPS system? What are we trying to protect, and from what? I have read that it has to do with grounding and neutral but I didn't ...
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1answer
107 views

Pulse transformer isolation on PCB

I have a question about pulse transformer ,regarding to isolation, EMI reduction and heating. My PCB has 6 layers (4 signal and 2 power planes) and I am using pulse transformer to isolate and ...
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1answer
64 views

Ground isolation

I am looking at ways to isolate my board and supply ground. I am feeding my board with a 40V dc power source. Now, the ground return of my board should not be connected to the battery return is the ...
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4answers
171 views

Short circuit when probing live ATX power supply primary section with voltmeter [closed]

I was probing around an old ATX PSU to inspect voltage levels in the primary section. The first 15 minutes went smooth (bridge rectifier inputs, big caps, Power IC Vcc, etc..) but as soon as I probed ...
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3answers
137 views

Boost converter for high side Mosfet

I recently came across an article explaining how to drive a high side MOSFET using a "separate isolated power supply whose ground and the ground of the MOSFET-based circuit are isolated". However ...
0
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1answer
131 views

What would the best way to filter high frequency noise? Decoupling/Bypass Capacitor? 1:1 Audio Transformer?

As many high end graphics card have high frequency coil whine and my particular one is causing whine on my diy studio monitors, what would be the best way to filter this noise? My studio monitors are ...
0
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3answers
444 views

Optocouplers with non-inverting logic

Here is the setup: I'm using the Arduino Mega's SPI functionality to send signals to multiple DACs. For digital isolation, I am considering the HCPL-2631 or the ACPL-064L. The problem with these two ...
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0answers
107 views

PCB isolation strength VS pad-to-pad distance

Is there any estimation regarding the relation between PCB pad to pad distance and isolation strength? If the board is covered with the mask and the minimum distance is 2,9 mm which isolation voltage ...
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2answers
69 views

SPI Isolation with Open Drain MISO

So I am trying to interface a slave device to a master uC through an ADUM4151 SPI Isolator and am getting confused on where I need pullups for the MISO line as I see it a few ways in reference designs....
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3answers
104 views

Can I ground the negative DC bus of a variable frequency drive?

Suppose I have a typical VFD: rectifier, DC bus caps, inverter, feeding a motor. In general it would not be advisable to tie the DC bus to earth ground, because the AC line may also be referenced to ...
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2answers
71 views

Isolation, level shifter [duplicate]

I want to to shift a signal which is varying from 1.2 to 3.3 volts ( a shifted square wave) to some other ground. I don't how to do this. Frequency of this signal is 10 kHz with duty cycle around 10-...
3
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2answers
161 views

Isolation transformer and AC potential between grounds

Wisely (I think) after connecting my DUT (Tektronix 2710 Spectrum Analyzer) to an isolation transformer, I measured AC voltage between the DUT chassis ground and my scope (Tektronix 2440) ground lead. ...
3
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2answers
99 views

Timing Issues with Optically Isolated Data Signal

I have been working on a system that requires data transmission between two devices powered by separate supplies. I have based my design on the MIDI-hardware Spec, as I'm comfortable working with that ...
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1answer
94 views

Why is ground shared between primary and secondary side in LT3750 circuit example

LT3750 is a capacitor charger controller IC. The sample (typical application) circuit in its datasheet shows an otherwise isolated secondary side sharing a ground with the primary side. A PCB layout ...
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0answers
51 views

Isolated CAN and Onewire

I have a bord where HV is present and one where only LV is presented. On each board is an Onewire und a CAN bus. How can I isolate the buses? I found for CAN this: http://www.ti.com/lit/an/slla298b/...
3
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1answer
185 views

How can I use an oscilloscope to measure voltages that are referenced to nodes several hundred volts apart?

In my organization, we often use four-channel oscilloscopes to check out products. Each probe reference might be several hundred volts away from the others, which makes using standard scopes ...
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1answer
102 views

How to isolate the microcontroller from power source?

I'm fairly inexperienced in electrical engineer so forgive the simple question. Using a microcontroller (Netduino) and two 8bit shift register (serial in, parallel out) I'm controlling 16 LEDs. The ...
0
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1answer
25 views

Is there a way to measure current and fault current better than the ACS716KLATR-6BB-T

I need to measure 2.5A (ac) and detect fault current. Currently I am using a Isolated Current Sensor with Overcurrent Detection ACS716KLATR-6BB-T Datasheet I am using this part because space is the ...
2
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2answers
104 views

Do we need isolate the MCU from the relay driving transistor

This question came to me when I saw this question driving a relay with transistor and Opto-isolator. As Olin Lathrop had pointed out in his answer, relays already provide isolation between the coil ...
3
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2answers
112 views

Is there any bidirectional IC with on/off state?

I need a bidirectional IC with on/off state. In on state, IC should have very small impedance on the line. In off state, IC should provide very high impedance to isolate the bus. It's for an 3-...
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1answer
52 views

What design considerations determine what kind of power supply I should use for a high-side FET?

I'm presently considering building a half-bridge converter, which means I have a transistor that's not tied to circuit common. To drive it, I'll need some voltage supply referenced to its source. This ...
5
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2answers
214 views

Opto-isolator output from collector vs. emitter

I have an Isocom ISQ2X quad opto-isolator (datasheet) that I will use to drive a logic input. The opto-isolator's simplified model given by the datasheet is pictured below. The transistor base pin is ...
0
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1answer
47 views

How can an isolating tape be used as a connection to the human body?

I'm making this project: Drawdio There are 2 connections with the human body: one via the graphite and the other with a grip made of isolating tape. I don't see how this work. This tape isolates the ...
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2answers
224 views

Capacitive Galvanic Isolation [closed]

One can create a very cheap and easy to build capacitive galvanic isolator for low freq (audio)? In+ --||-- Out+ In- --||-- Out- Adding resistors does not help ...
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2answers
136 views

Is GND isolation required to parallel a large number of power supplies

Suppose I have something like 50 independent switching regulators all tied a single load and ideally sharing current. I could provide isolation for each regulator using a diode. simulate this ...
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2answers
135 views

Self-powered USB device isolation

I'm designing a USB device (a 3D printer board) which I want to power from an old PC power supply and use the USB only for communication. My understanding is that both the power supply and my PC are ...
0
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2answers
115 views

When using USB and external power, how should I isolate the grounds?

I want to connect USB to my ATmega32U4 microctroller, which is powered by an external power supply. I was thinking it might be possible that the USB +5V/GND would be different than the +5V/GND I am ...