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

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13
votes
1answer
447 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
47 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
31 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 ...
6
votes
8answers
891 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
40 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
39 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
1answer
94 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
66 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
103 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 ...
4
votes
2answers
98 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
41 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
55 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
121 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
76 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 ...
1
vote
4answers
161 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 ...
2
votes
1answer
92 views

How to decide whether or not to use isolation in a circuit that has a microcontroller and a 48V DC supply?

A potential divider connects a 48V(worst-case) battery supply and a micro-controller for voltage sensing. Is it enough if I take care of the resistor values of the potential divider so as to limit the ...
0
votes
1answer
69 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 ...
0
votes
2answers
101 views

Is it possible to use capacitor for isolation instead of optocoupler?

I designed a Buck converter which drives several LEDs. The PWM signal, which has a certain fixed duty cycle, is generated by a 555 timer IC. The circuit which drives the Buck MOSFET, including the ...
1
vote
2answers
116 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 ...
0
votes
1answer
194 views

Noisy Voltage Rails (Vcc, Gnd) - Noise Isolation for Automotive Circuit

I have an audio (mic, speaker) circuit that I am currently powering off of a 12V car adapter that is fed into a 10V switching DC regulator to power the rest of the circuit. I have noticed a horrendous ...
1
vote
5answers
119 views

How do metal cases work with connectors & isolation?

I have troubles understanding how do metal cases behave in some cases. Case 1: I made passive attenuation box for amplifier(basically L-pad resistor), simple configuration: Amplifier => attenuation ...
4
votes
1answer
87 views

ADuM1301 digital isolator - PCB layout question

We are using the ADuM1301 digital isolator in one of our designs. The PCB layout section from the data sheet states: In applications involving high common-mode transients, care should be ...
0
votes
1answer
180 views

What is the difference between TO-220F and TO-220FP cases?

Google search results implies TO-220FP to be full-pack case. Wikipedia says that TO-220F is full-pack case. Farnell categorizes TO-220F and TO-22FP differently. I'm confused. What is the difference ...
0
votes
2answers
68 views

Passing control voltages to multiple isolated power supply channels

I'm designing a programmable bench power supply (PS) that has multiple isolated channels (each powered by a separate transformer winding). I like the idea of isolated channels so that multiple ...
1
vote
2answers
117 views

How to make a RF Additive Mixer for two inputs in same frequency band?

One of the most common designs for a SSB modulator (phase shift method) involves an additive mixer as the very last stage. Here is a block diagram for reference: This additive mixer must provide ...
4
votes
1answer
164 views

Do I need to isolate the output voltage feedback in SMPS?

I almost finish with my Half-Bridge SMPS design. I'm now designing the output voltage feedback to the controller stage. The controller stage drives both MOSFET transistor through an isolation ...
2
votes
4answers
259 views

What is an appropiate way to isolate a DC signal?

The question might sound kind of funny, but I'm unsure how else to word it. So... Pictures!! Currently, I have a setup like this: simulate this circuit – Schematic created using ...
0
votes
1answer
202 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 ...
3
votes
3answers
272 views

Ways to isolate DC power source

I need to isolate my circuit from the power source of 5V dc. Since this is for medical use, and the device is powered by USB, the isolation needs to be at least 4kVrms, 5mm clearance, 8mm creapage ...
2
votes
1answer
111 views

When an isolation transformer is not enough? [closed]

I work for a fairly large church and we have powered line array speakers that do not have attenuators in them. Over time a ground loop occurred from the stage lighting causing a very distracting ...
0
votes
1answer
89 views

Isolating polarities on a series wired battery bank

Can anyone, with 100% certainty (that means you know what you are talking about) tell me how to "isolate" the positive from the negative posts electrically in one direction so I have a true 'positive' ...
0
votes
1answer
132 views

1:1 isolation transformer fuse on secondary side - an option?

We sometimes use an old self build 1:1 isolation transformer (150VA) in our company to isolate devices under test. It is equipped with a primary 500mA fuse (slow) in series with a on/off switch. ...
2
votes
2answers
56 views

Separating / Isolating the circuit blocks

I was designing the circuit of a superhet receiver, block by block. Needless to say, my concern is how would I separate the various blocks. In other words, how would I interconnect the blocks ( not ...
2
votes
3answers
188 views

Galvanic Isolation with Voltage Equalization?

I need to equalize the ground voltage between the input and output of an isolated DC-DC power supply while still maintaining galvanic isolation. Is there a way to do this? The reason I need this is ...
0
votes
2answers
118 views

Isolation Transformer Safety

I recently purchased an armax 230 ISOTRAN Model 1521. I can’t find it on the web anywhere, and from what I understand it is an isolation transformer that takes in 115 VAC and outputs about 210 VAC. ...
1
vote
3answers
73 views

Low power Analog signal Isolation

In my project, the current budget is very tight. With less than 1mA, I have to isolate sensor's signal voltage and be able to measure it with ADC on the other side of the isolation barrier. What I ...
1
vote
1answer
232 views

Isolate two Arduino analog inputs

I have a stereo VU meter. (Audio in on Arduino pins A0 and A1 and GND to common GND also 32ohm resistors going to GND on A0 and A1 to simulate coming speakers) Now my problem is software architecture ...
1
vote
1answer
348 views

Isolating PWM From H-Bridge

I have a H-bridge based on FAN7392 drivers. This bridge works at 350VDC to output a approximately 240V 50Hz waveform. This circuit is isolated from rest of the board and I would like to maintain the ...
1
vote
1answer
84 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
1answer
67 views

Should AC voltage supplied to an external device through a relay be electrically isolated from the main power source of the enclosure?

Given a power supply in an electrical enclosure powered by 120 VAC. An I/O device will trigger a relay with a 24 VDC control. The signal from the I/O device will enable the relay for a set duration. ...
8
votes
3answers
953 views

Are there any disadvantages using magnetic couplers instead of opto-couplers?

I'm trying to find the disadvantages of using magnetic couplers versus opto couplers (1). I'm deciding which of the two I should use to create a galvanic isolation between two PCB's that are going to ...
1
vote
1answer
103 views

What is this Circuit's function? Does it involve Isolation?

My question is: Does this circuit isolate the "X Volts" lines from ground (1) If not, how should I implement an opto-coupler to provide isolation between the data lines ("X Volts") and ground? ...
2
votes
1answer
111 views

How to work out or calculate this circuit?

I'm not an engineer, I understand a lot but I fail to understand how it works and how to calculate this for a 24vdc input:
0
votes
2answers
226 views

Isolation of CAN-High and CAN-Low signals [closed]

I have to isolate the signals CAN-High and CAN-Low on a CAN bus. Is there an isolated CAN repeater (something like IXXAT's CAN-Repeater - 110 × 75 × 22 mm) which would be ...
11
votes
2answers
1k views

Why AC points on PCB are separated by a hole

I want to find out why, in professional PCB's, they separate between the AC (220 VAC) points on the PCB with a hole in the PCB: Is it for more isolation between the AC lines? Is leaving a distance ...
2
votes
3answers
219 views

I2C isolation; 3kV

I am working on a high-side current sensor, where the high-side is around 3kV. I have come to the conclusion, with some help from you kind folks, that it is best that I float the majority of my ...
1
vote
0answers
154 views

How to isolate DS2406 switch from mains? [closed]

I would like to use a DS2406 1-wire control chip to switch a mains load. Isolation is required and I would like to use the 1-wire supply. There are no power supply at the remote end, only 1-wire ...
1
vote
4answers
346 views

Powering an AMC1200 Isolation Amp

I need to measure a very small current at the high-side of a circuit. The high side is at 3000VDC. The measurement needs to ultimately be in the form of a signal with a peak of no more than 5V, so ...
3
votes
1answer
182 views

Proper power design for a USB device

I'm designing a USB device that I want to be powered eintirely from a wall wart and have a couple questions concerning the power connections and ground loops. 1) If I connect the USB GND pin to ...
3
votes
2answers
587 views

Why DisplayPort cables must isolate the power pin?

I've been investigating why my 2560×1440 DisplayPort monitor and my mini-DisplayPort MacBook Air don't play along, and, it turns out, this is likely due to a wire in the cable that connects the two ...