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

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2
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2answers
673 views

How to isolate low voltage control circuit from high voltage power circuit?

Can anyone give me a brief run-down of some methods I could use for this? I want to drive a MOSFET or BJT with a 12v 555 circuit or oscillator. The MOSFET will drive a high voltage circuit that ...
0
votes
0answers
71 views

SPI Communication fails with ISO7241C but works with ISO7641FC, same circuit?

Objective: To interface DAC161S997, with Microcontroller C8051F350 through ISO7641FC using SPI Protocol, Which works fine and DAC output is achievable. Now here is the problem, I have changed ...
0
votes
1answer
32 views

Do I need to place any additional component(s) getween isolated grounds?

Initially I bothered with this question regarding isolated flyback switch mode power supplies. However I'd be happy to investigate this question dipper. So as the output of the power supply is ...
2
votes
1answer
116 views

How do I pick an inductor(s?) for an LC filter on a power rail?

I'm using a TI SN6501 transformer driver to provide an isolated power supply for a project I'm working on. However, it is imperative that the output power rail be as clean and noiseless as possible, ...
0
votes
1answer
74 views

floating ground for AC and DC power supplies

I wanted to connect two power supplies, one is AC (240V , 6A) and the other is DC (3,3V, 300mA). But i read in some referrence that connecting AC and DC power supplies could be dangerous if the two ...
0
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0answers
39 views

Recommendation for Overvoltage Protection

I am now trying to design an adapter between an inverter and a simulator. I actually need to do some protection for the very expensive simulator on the design. I did my job for digital signals with ...
0
votes
1answer
22 views

Power Metal Oxide Resistor - Maximum pulse voltage

I am looking for a suitable series resistor (220k) for a 230VAC optocoupler input. The device must meet requirements from EN60664-1. I am still trying to understand the final requirements, but from ...
3
votes
1answer
44 views

Can a FELV circuit be connected to a SELV circuit?

This might be a very very simple question, but I'm unsure how to interpret the rules. I have a circuit which switches 230V using relays. The circuit is a motor controller for a motor control box ...
0
votes
1answer
82 views

Switching Regulator Ground Moating

I have a DC-DC switching regulator that operates at switching frequency of 260Khz that steps down a 28vdc to 3.3Vdc. On the same PCB I have a microcontroller and would like to have it's ground plane ...
0
votes
1answer
31 views

Pulse Supply Ground Reference

I am currently working on a high voltage supply for short (50-100ns), quick (<30ns rise time) pulses. The below circuit is my first rough draft for the power supply, I realized that by connecting ...
1
vote
1answer
55 views

Transformerless stabilized power supply for isolation amp

I'm building a circuit similar to this: https://courses.cit.cornell.edu/ee476/FinalProjects/s2008/cj72_xg37/cj72_xg37/ (voltage and current sensing of a 230V line) I'm using two HCPL-7520 isolation ...
0
votes
1answer
30 views

Using ADuM3150 for SPI Interface with Arduino

I am trying to use an isolator for SPI communication with the Arduino. I am presently using the ADum3150. You can find the datasheet here. There are some delays associated with this arrangement and ...
0
votes
0answers
46 views

What parameters are key in selecting a transformer to pass digital data?

Looking to fiddle around with some digital signaling through transformers. Never done, so this is just to experiment and see what it looks like. For the purpose of digital isolation, what types of ...
13
votes
2answers
10k views

What values of resistor and capacitor to use for AVR reset pin isolation?

Background... I'm a newbie to AVR applications. I recently built two ATTINY13-based circuits (glorified LED blinkers) which worked correctly (independently) on the breadboard. When I combined them on ...
0
votes
1answer
79 views

Power regulation and isolation for low current device

I'm looking for a solution to regulate power and provide isolation for a 3.3VDC system. I am using a 5VDC 500mA power supply that needs to be regulated to 3.3VDC with isolation to protect analog ...
6
votes
2answers
6k views

Is galvanic isolation of Hi-speed USB impossible?

I have a USB isolator which provides galvanic isolation of a USB device from my PC, but only works for low speed and full speed USB. I can't find any alternative electric isolators which do provide ...
1
vote
2answers
71 views

Grounding a 30KVA isloation transformer

My company does audio visual services. When we use a single 120/208 VAC Three-phase "Y" power source for lighting, audio and video we get noise caused by the lighting dimmers injected into the audio ...
3
votes
1answer
43 views

Purpose of deleting internal PAD

I just learned today that, when you're routing the board you can delete the pad of through hole connectors on the internal layout. Some company even ask to delete all the internal pad that are not ...
0
votes
1answer
2k views

Effect of an isolation transformer on leakage current

How do isolation transformers affect the leakage current through protective earth in a system? Scenario 1: Mains is directly connected to circuit. Metal enclosure has a protective earth connection ...
0
votes
1answer
59 views

In what order should I isolate and attenuate an audio signal?

I have a cheap bluetooth audio module (with no documentation) that outputs a signal greater than line-level. It was probably designed to be connected directly to small speakers, since the ground on ...
2
votes
2answers
79 views

What are options for an optically-isolated power supply?

I'm considering options for an isolated power supply (1mA @3V) with very low noise pickup and capacitance to mains/ground. Is there a simple optically-isolated solution, preferably using an ...
2
votes
2answers
133 views

How much is a transformer's secondary floating?

Consider an isolation transformer with its secondary referenced to ground via a resistance R as in the following picture. simulate this circuit – Schematic created using CircuitLab If R ...
0
votes
1answer
80 views

Can 0V from an isolated source arc to earth ground?

I have a high voltage bus bar (~300-400VDC) that is powered by a variac. This sits in a case that has other electronics that are powered by a step down transformer (120VAC to 24VAC, then rectified to ...
0
votes
2answers
103 views

Understanding to isolating sensor input capacitance

The circuit given above is pH sensor buffer circuit, picture taken from here. This circuit have pH sensor input and gives an output that can be read by multimeter which is U2's OUT_ pin . U1 is here ...
1
vote
2answers
91 views

Mains isolation is mandatory for UL/CE/CSA compliance and other certification?

I have a design with a non user accesible low voltage section. Is mandatory to do mains isolation to pass succesfully UL/CE/CSA despite my low voltage section is not accesible for user?
2
votes
1answer
92 views

Isolation for loop powered devices with limited power

I am implementing 4~20mA Transmitter that consist of a MCU, a current DAC, and an ADC for measuring an analog signal. I would like to electrically isolate the analog signal from the loop current so ...
0
votes
0answers
24 views

Unregulated Forward Converter for Galvanic Isolation

It seems to me that I could use an unregulated forward converter to provide galvanic isolation and then use a DC-DC converter to provide the voltage regulation. I'd use a two switch forward converter ...
0
votes
1answer
39 views

Optoisolated Feedback Pin Operation

In the case of galvanically isolated AC to DC converters, a controller IC is used to regulate the output voltage of the converter. The feedback pin is fed a signal from an optoisolator driven by the ...
2
votes
2answers
121 views

What is the source of leakage current thru an isolation transformer?

I want to use my oscilloscope to check the cleanliness of the output a high-voltage power supply (electrophoresis type, up to 3000 volts DC). I built a 100:1 voltage divider (out of 2 resistors - ...
0
votes
2answers
87 views

DIY Isolated Power Strip?

Would it not be ok / safe to take a surge protector style power strip, cut the mains cable in the middle (or maybe slice it open and just fish out the load and neutral wires so that the ground wire is ...
0
votes
1answer
54 views

isolation between lcd 20*4 lcd and tm4c123 [closed]

power suply required for my launchpad is 3.3 v and that required for lcd is 5 v. I want to isolate lcd and launchpad. What should I do? do i need to put optoisolator between each pin of lcd and ...
1
vote
2answers
77 views

Ground loop noise goes away when heater comes on [closed]

I have a ground loop or something in a stereo wiring. I have 3 stereo's connected all with the same inputs(fanout). One stereo several feet away from the other two has an annoying amount of hum. ...
15
votes
1answer
655 views

Isolated DC/DC Converter - Purpose of Capactor connecting two GNDs?

I've been looking at board mount isolated DC/DC converters to use in an application. I found this rather reasonably priced for my needs. Here is what I'm confused about, what is C103 doing here? Isn't ...
0
votes
2answers
66 views

FPGA power input isolation

I am working on a design that has at least a dozen FPGA's. In the past I have had an FPGA get damaged by a faulty voltage regulator and short out the supply input to ground.Chasing down which FPGA ...
0
votes
0answers
94 views

DIY HV Tube Isolation Transformer

I am making a bench top tube power supply from salvaged transformers. I want to make it as safe as possible so I am checking here before the build. The two 120V/20V transformers have electrostatic ...
19
votes
5answers
8k views

Why is it important for mains power supplies to be isolated?

In all the computer power supplies and other power supplies I've taken apart, I've noticed they are fully isolated from the mains. Galvanic isolation through transformers, and often optical isolation ...
6
votes
8answers
1k views

Why are we not always isolating the mains supply?

Something struck me: to protect people, the neutral of the supply is connected on the supplier side to Earth, so that leakage through ground is detected when for example someone touches the phase ...
0
votes
1answer
71 views

Isolation on outputs

To measure a voltage in a (potentially dangerous) external system, people typically use a differential amplifier or even an isolation amplifier, something like this: simulate this circuit ...
1
vote
2answers
323 views

RS-485 isolation required?

I would like to confirm my understanding. Suppose I'm want to have two battery-powered MCUs inside an (unmanned) aircraft communicate with each other via RS-485. If those MCUs are powered from the ...
1
vote
1answer
111 views

Is using a transformer at reduced voltage a bad idea?

My Google is failing me. I want to make an isolated AC voltmeter capable of working at 120 or 240 VAC. I've found a suitable 240 volt to 5 volt transformer to use (current capacity doesn't matter - ...
0
votes
1answer
106 views

Class II isolated power supply (wall wart) — referencing the output to mains neutral?

If you connect the - terminal of a Class II (isolated) wall-wart-type power supply to the neutral of the mains circuit feeding the wall wart, will that cause any damage or hazards that I should be ...
1
vote
4answers
131 views

Low component count isolated contact closure without power on the remote side

Other answers here show a common way to allow a microcontroller to cause a contact closure (button press) within another device in an isolated fashion: use an optoisolator. I have the reverse ...
5
votes
2answers
136 views

Optocouplers for purposes other than galvanic isolation?

In the diagram below there are two modules, A and B, which are separated by a physical distance of about 15m. Module A has a 12V DC power input. Module A powers module B (they share a common ground). ...
0
votes
1answer
59 views

Using a ferroresonant regulating transformer as an isolation transformer

I'm looking to use a (surplus, NOS) Sola (catalog number 22212) ferroresonant voltage regulating transformer (120V primary and secondary) as a low-power isolation transformer (4A) in case I need to ...
0
votes
0answers
58 views

Full Speed USB Isolator

Can anyone suggest a way to galvanicaly isolate a USB Full Speed (12Mb/s) signal with a solution height of less than 2mm? Parts like the ADUM3160 (link) and ADUM4160 exist but they are too tall for my ...
3
votes
2answers
147 views

Are IC sockets suitable for mains voltage?

I need to derive a low-voltage galvanically isolated 50 Hz signal from 230 V mains. I'll use an opto-isolator for this. I'd like to use IC sockets for all ICs in this personal one-off project. ...
0
votes
1answer
82 views

Earth alternative

I'm designing an industrial machine which is AC motor derived. There are sensitive analog sensors (e.g. Load cell) in the system and in the user's site, Unfortunately earth connection is not ...
0
votes
1answer
254 views

Oscilloscope ground and unit under test ground issue

I am working with an instrument which has a supply of 230V AC or 400V DC. AC source is isolated at the input via 1:1 transformer and DC source is a floating supply. I have a Yokogowa DL1620 ...
1
vote
4answers
217 views

Relay alternatives that are silent and support 500mA+

What can I use as a silent "general-purpose" relay alternative? There are various scenarios where I will need a relay-like device that allows me to control one circuit with a separate isolated ...
0
votes
1answer
98 views

Need to isolate panel meters from each other?

I have a computer power supply I am planning to use for electronics work. I was planning to make a box with voltmeter/ammeter panel meters on each output voltage (3.3V, 5V, 12V, -12V). I have read ...