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

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1answer
49 views

Microcontroller to PC via USB - do I need to use isolation?

I want to connect my microcontroller (dsPIC33E) to a PC via USB. Since the particular microcontroller doesn't have a built-in hardware for the USB protocol, I have to use an external chip (e.g. ...
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1answer
74 views

Will the use of an isolation transformer improve the safety of my power supply?

I have a power supply design that makes use of a half-wave rectifier and a non-isolated buck Swtich Mode Power Supply IC to step down 120V 60Hz AC power to 12V DC. I then use a Linear Voltage ...
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2answers
57 views

Efficient method for isolated detection of AC voltage without a stepdown transformer

What is an efficient method to detect the presence of Line AC power in an isolated method? My first thought would be to use an optocoupler, but in order to do that, you need to supply the current ...
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0answers
45 views

How do I correctly power a USB 2.0 while decoupled from signal?

I'm building a switch that will power on / off a bunch of USB 2.0 ports. In order to avoid overloading the USB hubs (as has been an issue in the past) I would like to power and switch my peripheral ...
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0answers
48 views

If I connected a voltimeter between a galvanically insulated phase and ground, what voltage value would it show?

I got asked that question and got me to doubt. If I had two phases L1 and L2 and N, all galvanically isolated using an isolation transformer, and I were to measure L1 vs ground, what voltage would the ...
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1answer
24 views

Unserstanding of “Maximum repetitive peak isolation voltage”

Sometimes optocouplers has only Isolation test voltage parameter. Sometimes it has a bunch of parameters regarding isolation strength, including Maximum repetitive peak isolation voltage. Strange ...
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0answers
49 views

Isolation Amplifier Design Issue

I modulate input signal with triangle wave to create PWM signal. When I am creating triangle wave I use astable multivibrator and integrating circuit. unfortunately there are offset at my triangle ...
0
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1answer
31 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 ...
0
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1answer
37 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
18 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
123 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
61 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
109 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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0answers
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 ...
1
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1answer
46 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 ...
0
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1answer
27 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....
0
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1answer
69 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
53 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
21 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
113 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
277 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 ...
0
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1answer
49 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 ...
0
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1answer
85 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
49 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
99 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
50 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
235 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
45 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
280 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-`, ...
0
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1answer
269 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 ...
5
votes
3answers
825 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 ...
0
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1answer
111 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
67 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
192 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 ...
2
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3answers
152 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
156 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
531 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
115 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 ...
0
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2answers
76 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....
0
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3answers
120 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 ...
0
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2answers
75 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
votes
2answers
175 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
votes
2answers
103 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 ...
1
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1answer
108 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
52 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
votes
1answer
187 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 ...
1
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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
109 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
118 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-...