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Questions tagged [mains]

Mains electricity, typically a higher voltage AC waveform used to deliver electrical power to households. In North America 120V, 60Hz, in most European countries 230V, 50Hz. What most people will plug appliances into.

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Using Microchip Technology MCP39F521 (I²C Power Monitor) with 240V

In the sample schematic Microchip Technology supplies in the data sheet for their MCP39F521 shown below, it appears that V1- is grounded. (V1- and V1+ are input pins for determining voltage.) Does ...
Eric Lindsey's user avatar
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Acceptable resistance between hot (mains) and ground (earth)?

A DIY project I'm working on uses electronics embedded in concrete, including 110V AC heating elements. As I was verifying my wiring before testing the device I was surprised to discover conductivity ...
sirbrialliance's user avatar
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Explination for arcing noise coming from protected power tap devices?

For years now there has been a random occurrence that happens with seemingly any power tap device I have with protection circuitry in it where it will make a audible buzzing/arcing sound for a few ...
Jacob Jewett's user avatar
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5 answers
206 views

What frequency do long-distance undersea powerlines run at?

I recently saw this photo of the project "NATO-L", or North Atlantic Transmission One-Link. It's an under-sea powerline planned to connect Europe with North America. Does anyone know what ...
spinjector's user avatar
1 vote
0 answers
62 views

Safety considerations for designing Mains Voltage Sensing Circuit

I'm looking to design a circuit to measure AC mains voltage and current for protection purposes. I'm considering using the ADS131E0 ADC by Texas. The IC is made with power-line monitoring in mind. On ...
Dinis's user avatar
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2 answers
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Does it improve safety to make a capacitative dropper symmetric?

Here's the most basic capacitative dropper circuit I could find with ten seconds on Google. Allegedly the voltage across the load will be about 5V. (I say "allegedly" because I couldn't ...
zwol's user avatar
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-1 votes
1 answer
72 views

Does the center tap of a single phase distribution transformer get bonded to the grid neutral? [duplicate]

Here are the two wiring diagram.
Nhit C's user avatar
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1 answer
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Detecting and measuring AC line voltage with an optocoupler

I simulated the circuit shown below using MultiSim and obtained some interesting results. The simulation suggests that you can accurately reproduce the AC line voltage from the input to the output. ...
wogoos's user avatar
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2 votes
0 answers
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What are these extra wires on power lines?

The other day I was having a walk outside on a rural road and noticed something odd about the nearby power lines: What are these extra wires doing there? Context: Location - Europe, Latvia. This is a ...
Vilx-'s user avatar
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1 answer
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How to inject and extract a high frequency modulated signal onto and from the AC powerline?

I'm generating a square wave carrier signal of 125 kHz using 555 timer, I modulate it with a data signal generated from ATmega32 Tx pin (UART 9600 Baudrate) using OOK-Modulation, and now I'm trying to ...
Joe's user avatar
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2 votes
2 answers
326 views

Will an isolation transformer have a noticeable effect on mains hum? Also critique my DIY transformer idea

(Uber-edit - it has come to my attention that I am an ignoramus. This post is being left in place not to highlight my stupidity in particular, but to serve as a warning for others who think ...
neural's user avatar
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Broken ground conductor in single wire earth return (SWER) system

I have a property in a rural area that is serviced by a SWER line. This means we get one high voltage line from the utility into the service transformer, whose other leg is connected directly to ...
Délisson Junio's user avatar
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1 answer
48 views

Mobile Power Distribution Unit: Mains Cable Size

I'm currently working on constructing a mobile power distribution unit and I need some assistance with a specific aspect of it. The unit is designed to accommodate both types of power networks found ...
TTransrecord's user avatar
10 votes
3 answers
2k views

Why does this "hot chassis" TV have the inputs isolated by an active circuit instead of just a capacitor?

I was looking at adding a Y/C video input to an old TV. But it's got a hot chassis so it's not a trivial task. I thought i could just capacitively couple the Chroma line, but then i looked at the &...
hjf's user avatar
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1 answer
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Single frequency light at home

I’m very interested in making some art that’d require me working in single frequency light — specifically the monochromatic light from the sodium vapour bulbs historically used in street lights. I can ...
JP.'s user avatar
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2 votes
3 answers
380 views

Safely grounding 120V AC device

I'm pretty new to electronics. I'm building a device that has an aluminum enclosure, is powered by a 120V AC outlet, and requires roughly 520W of total power. My circuit is: AC input with a hot, ...
Sohil Sathe's user avatar
1 vote
1 answer
82 views

Order of pins for AC mains connection to PCBs

I am designing an AC mains connector footprint in KiCAD which will be implemented using three 4.8 mm faston tabs for line hot, neutral and ground. Is there a norm or preferred order for the order of ...
Joe's user avatar
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1 answer
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How is unequal current flow created?

This video discusses residential power distribution systems, and the magnetic fields that surround them. At the 36 second mark of the video, the presenter states We have a distribution line issue ...
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1 answer
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Earthing connections in cascaded UK mains power supply

I've just looked at a power supply for a client to try and diagnose some other issues, and I noted that the connections weren't what I expected. The supply is cascaded, one isolated UK mains to LV DC ...
LordTeddy's user avatar
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Zero crossing circuit with phase control

Beginner here. I am trying to make a "zero crossing" circuit with phase control. This is probably not the right name for the circuit. Basically, I have a sine wave (from the power outlet) at ...
DarkBulle's user avatar
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1 answer
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Measuring if a capacitor on mains is turned on by measuring radiated electrical fields far away

There is a house connected to German mains with hot, neutral and ground. Some distance away in the village there is a PWM source (most propably a solar inverter) which shows as 17kHz on the mains ...
Hansebenger's user avatar
0 votes
3 answers
62 views

Positioning of Inductor and Capacitor for Mains Voltage Noise Filtering

In the datasheet of this power supply, it is recommended to place the capacitor before the inductor for the mains voltage filtering circuitry, as it is shown on this image featured on the datasheet: ...
Dinis's user avatar
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1 vote
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Handling higher clamping voltage of IsoMOV - MOV/GDT Hybrid

I'm working on an ac mains control circuit and came across IsoMOV a new hybrid MOV/GDT for surge suppression. This appears to be a straightforward replacement for a standard TPMOV with additional ...
fivejeez's user avatar
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1 vote
1 answer
119 views

Phase neutral earth fault indicator circuit

I came across the following circuit on a random website: Source website My guess is this circuit is used by some extension boards as shown below: I understand that LED1 current (around 2 mA) is ...
Whiskeyjack's user avatar
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What is the most efficient way to detect if AC mains is live for interfacing with a microcontroller?

I want to implement an electrical mains level detector to interface with a microcontroller the simplest and most efficient way possible as this circuit would always be on. I’m trying to detect when a ...
fivejeez's user avatar
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0 votes
2 answers
566 views

Charging a mobile phone and laptop using wall plug - Series or parallel circuit?

I'd like to understand if charging multiple devices using the 240 V line's main power plugs forms a series or parallel circuit.
9_daytona's user avatar
0 votes
1 answer
59 views

Seeking a good solution for mitigating the effects of high in-rush current caused by an AC-DC converter [closed]

Many AC-DC power supplies (say, 220VAC to 24VDC) have huge inrush current values. For example, a device might have an inrush current of 80A@230VAC. This raises the question of how to handle the ...
Dmitri Nesteruk's user avatar
2 votes
1 answer
104 views

AC line filter polarity

Currently I working on very simple AC power mains distribution board. I want to use PCB-mounting AC line filter SCHAFFNER FN405-10-02 for EMI reasons. The datasheet provides simplified schematic: ...
plumbum_by's user avatar
0 votes
2 answers
47 views

For an active power factor correction circuit (PFC boost,) is there any characterisation graph between input voltage and power factor?

Just like the regulation graph (ouput voltage vs. input voltage) for a voltage regulator, is there a similar graph (power factor vs. input voltage) for a power factor corrector circuit? My aim is to ...
Dynamic_equilibrium's user avatar
0 votes
2 answers
55 views

Mains transformer input overvoltage protection

You have a mains transformer with switchable inputs, 120V and 230V. In case somebody switches the input to 120V and applies 230V (which cannot be mechanically prevented, reasonably), the whole ...
Michael B. Ortiz's user avatar
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1 answer
84 views

USB Audio interface 50Hz + harmonics noise when either laptop or speakers are plugged in

As soon as I plug in either my laptop or my speakers to the wall, I get an unbearable amount of noise in my guitar recording. Signal chain: Guitar --(1/4 jack)-> Audio Interface --(USB)-> PC --(...
Elite_Dragon1337's user avatar
5 votes
3 answers
120 views

Programmable current-limit on mains

Using an incandescent light bulb in series with a mains-powered device is a well known trick to limit the current used by the device. It's great for testing devices you're unsure of. Unfortunately, ...
Celelibi's user avatar
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3 votes
0 answers
126 views

Measuring 115 V on microcontroller analog input

I've been tasked with switching a number of 115 VAC, 60 Hz supplies to various pieces of equipment, and monitoring these output supplies on a PIC18. I'm confortable with the PIC and ADC side, but ...
Dan Twining's user avatar
0 votes
1 answer
180 views

What is the exact reason for grounding (earthing) of a transformer? [duplicate]

I have some misunderstandings with the grounding of a transformer. As far as I know, the utility transformer's (the last transformer before my mains plug) neutral point (star-connected point of 3 ...
electroeso's user avatar
0 votes
2 answers
157 views

Power electronics on a PCI/PCIe expansion card

I'm not sure if its been done before but how feasible is the idea of building an computer expansion card (PCI/PCIe) that carries mains power on some areas of the expansion card being switched by ...
dazzleworth's user avatar
2 votes
1 answer
128 views

Is it safe to use 250V rated relays with UK mains voltages?

UK mains voltage is 230V (RMS) with a tolerance of -6% and +10%. That gives it an upper limit of 253V (RMS). Lots of relays are rated up to 250V: e.g. the Omron G5Q series has a "rated ...
Rob Gilton's user avatar
2 votes
0 answers
71 views

Philosophy of safety by Double Insulation

In a Class I appliance, when a fault occurs that brings dangerous voltage in contact with accessible conductive parts, the installation wiring fuse or GFCI will not only shut down the dangerous ...
tobalt's user avatar
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1 vote
1 answer
107 views

TRIAC controlled fan output on furnace control board not working

At board power-on, the fan output connector has mains (230V AC) voltage without the fan connected, that drops to ~2V AC with the fan connected. At power-on, on the attached display, the board shows a ...
gdee's user avatar
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2 votes
0 answers
200 views

ESP32 with two power supplies (AC/DC + USB) using Schottky diodes

I'm building a small circuit to power an ESP32 with two different power supplies. Normally the circuit will be powered from AC, using a Mean Well IRM-02-5 AC-DC power supply to get 5VDC out of 220VAC. ...
Daniel P.'s user avatar
0 votes
1 answer
156 views

Schematic of a simple zero-crossing triac switch

I have a triac in a 60Hz 120V power line (as is often done for dimming) and want it to only switch on the power when the AC voltage is low (widely between -40V and +40V would even be fine). This is ...
bobuhito's user avatar
  • 554
19 votes
5 answers
4k views

Why does grid voltage drop at 10pm?

The premise of the question may be the problem so please let me explain first. In my home at night we have a bunch of nightlights and we run a small fan in each bedroom for the noise and/or cooling. ...
Aldus Bumblebore's user avatar
-1 votes
2 answers
3k views

Power supply makes a static/coil whine noise when the power supply is off and the PC is off

I have noticed that my power supply (PSU) makes a VERY slight coil whine/static noise while it is plugged into the power outlet, regardless of the power status of the PC and the PSU. It sounds no ...
P. Z.'s user avatar
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1 vote
0 answers
89 views

Reducing Isolation Transformer Leakage

I watched this video and wonder if its complete separation of primary and secondary coils is the normal way to wind a low-power isolation transformer (e.g., 60Hz 120V 120VA). I particularly want low ...
bobuhito's user avatar
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0 votes
0 answers
45 views

Connecting GND to PE to improve touch sensors sensitivity

I am designing a smart light switch based on a microcontroller, with touch buttons. The design consists of two PCBs: a low voltage one for power (230 V) and an extra low voltage one for control (3.3 V ...
Elzaidir's user avatar
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0 votes
1 answer
694 views

Minimum wire size for a 32Amp breaker

Problem statement: Sailing boat with a 16A onboard breaker need to connect to a 32A onshore power supply. What is the minimum cable size from the onshore 32A breaker to the onboard 16A breaker. Under ...
CaptainMJ's user avatar
1 vote
2 answers
192 views

How can we safely test a mains powered device?

We have small non-isolated 230VAC devices that transform mains to LEDs running at 32V, 20mA. The lights are directly connected to live, neutral and earth like a standard lightbulb would be. Since ...
sandervd's user avatar
0 votes
0 answers
176 views

Controlling TRIAC with PWM from microcontroller

I am looking to control a mains heater with a microcontroller. It seems like most solutions use an optocoupler to signal the microcontroller at a zero crossing and another optocoupler to trigger the ...
Levi Applebaum's user avatar
3 votes
0 answers
66 views

Identifying old Thermal Relay and its operating parameters

I was hoping that I could get help identifying an electrical component from a environmental chamber over 30 years old. It is a Sunvic Thermal Relay Type TDW-AJ 2301, 17A 200/250V AC as shown in the ...
MattG's user avatar
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-3 votes
1 answer
212 views

Should I connect a small DC motor directly to the mains without an isolation barrier? [closed]

I recently found out I'd need to pay upwards of $2k in order to supply my entire house with automated blinds. I feel like I can definitely do it myself for a fraction of the cost. For this purpose I'm ...
php_nub_qq's user avatar
4 votes
3 answers
399 views

Location of Galvanic Isolator in marine installation

Almost every installation diagram I have come across for a galvanic isolator, has the GI installed in the shore power input line as follows: I think can understand how this would make sense for a ...
Rowan Smith's user avatar

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