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

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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 ...
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1answer
43 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 ...
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1answer
56 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 ...
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24 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 ...
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42 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 ...
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2answers
58 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 ...
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1answer
42 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 ...
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1answer
58 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 ...
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2answers
78 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 ...
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1answer
71 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 ...
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2answers
105 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 ...
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1answer
77 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 ...
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96 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 ...
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70 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 ...
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2answers
84 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?
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23 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 ...
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1answer
38 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 ...
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2answers
111 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 - ...
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2answers
77 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 ...
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1answer
49 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 ...
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2answers
69 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
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1answer
628 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 ...
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2answers
64 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 ...
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74 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 ...
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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 ...
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1answer
89 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, ...
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58 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 ...
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1answer
106 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 - ...
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1answer
94 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 ...
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4answers
127 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 ...
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2answers
123 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). ...
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1answer
53 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 ...
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0answers
57 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 ...
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2answers
143 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. ...
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1answer
78 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 ...
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4answers
194 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
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1answer
97 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 ...
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1answer
89 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 ...
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2answers
178 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 ...
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2answers
254 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 ...
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1answer
469 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 ...
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5answers
150 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
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1answer
100 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
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1answer
606 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 ...
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2answers
97 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 ...
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2answers
154 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
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1answer
296 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 ...
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4answers
291 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 ...
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1answer
241 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 ...
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3answers
303 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 ...