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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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Is there a power socket selector/switcher (where only one of multiple devices attached is selected to get the power)

I'm looking for a device whereby I can choose which socket the power is directed to (in a similar way to a KVM switch for computers sharing a single (K)eyboard (V)ideo Display and (M)ouse, but in my ...
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How can I match phase voltage between a transformer primary and secondary?

I am trying to make a circuit to transform 240VAC, split-phase to a 0 to 5V waveform for an Arduino ADC so I can measure the mains voltage. I have read this question (How to measure line voltage (220V)...
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49 views

Isolating main power traces on backside of the PCB

I am currently making a build-in PSU for my own audio-effect-rack-thing. The internal PSU consists of two print-transformers(THT), one for 6VAC and the second one for 9VAC. These are also pretty low ...
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Why is there a voltage between the mains ground and my radiator?

I have an anti-static mat that comes with a plug that only has a ground lead. Out of curiosity, I measured the voltages between the live, neutral, ground, and my radiator. As expected, there is ...
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49 views

high voltage buck converter

I'm a second year EE student. I was trying to make some circuits by my self. I wanted to make a Buck-converter, from mains. I'm from India. Here mains are 220v to 230v 50Hz. My aim was to attain a ...
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64 views

Standard Powered Female DC Connector

Is there a standardized female DC jack designed to provide power, much like AC female wall outlets? Typically devices that require a DC power input are powered by individual external power supplies (...
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Replacing A Ceramic Hob With An Induction Hob [migrated]

If I were to replace my ceramic hob in my kitchen at some point in the future with an induction hob, would any rewiring be needed or from an electrical point of view, would it be a straight swap? (UK,...
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1answer
62 views

zero-crossing detection: to optocouple or not to optocouple?

That is the question. Most of the diagrams I have seen on the interwebs are of the opto-coupling school of thought: But the AVR182: Zero Cross Detector application note just throws in the resistors ...
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3answers
86 views

Is UL approval only required for the power supply?

Suppose a mains powered device has a PSU in the assembly that has a detachable cable to the mains. Is it just the PSU that needs to be UL approved/compliant? Is the whole device therefore UL-compliant ...
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79 views

Convert kW generated per minute to kWh

I have the data of power generated by a solar panel per minute in kW. I need to calculate the total number of kWh generated per day. How do I do this? So far, I divided each value of kW by 60 and ...
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2answers
106 views

How to detect a partial discharge in a noisy signal?

I am working on a competition where we are required to detect partial discharges in given signals. Each signal represents a measurement of some power-line voltage. I know that partial discharges ...
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57 views

Circuit for Neutral point of 3-Phase mains

I wonder if the 'Neutral Point' as mentioned in the attached image is correctly labeled or not? Is there any mistake in this 3-phase circuit design? Edit 1: Also it looks like the 'Neutral point' is ...
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1answer
60 views

Detecting mains power change: One signal when on, another signal when off

I'm trying to connect a timer output wirelessly to another circuit. These are on two separate power lines (different phases, circuit, long distance), so I thought of connecting them wirelessly, I'll ...
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49 views

Transformers and high voltage elements

I've been trying to learn how to properly set up a circuit for power regulation. Often I hear for domestic use that it is better to use a transformer to isolate the device as well as stepping down the ...
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1answer
23 views

Can I simply add a 240V Neutral to SONOFF TH10 when replacing wall thermostat

So, I have purchased a SONOFF TH10 wanting to use it to replace my wall mounted thermostat. The thermostat has 2 connections: Always-Live and Switched-Live (which is activated of course by the ...
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Can I use a 28 VDC 10 A relay to toggle a 10 kV DC 0.03 A source?

Neon signs use transformers that can output at 10 kV DC at 30 mA = 300 W. I want to toggle this power with a common 5 V relay, but the DC rating for these are about 28 V DC at 10 A = 280 W. Does the ...
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1answer
93 views

Is a safe 110/120VAC benchtop power tap possible?

I have a benchtop power supply that provides +3.3, +5, and +/-12VDC. I've started cannibalizing small appliances for parts, and I'd like to have similar power taps for 110/120VAC. Does such a thing ...
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2answers
44 views

Mains AC overvoltage protection using a TRIAC

I am trying to design a circuit that protects 127V appliances if plugged in a 220V socket (in Brazil 127 and 220V sockets have the same shape and it's easy to plug a 127V appliances in a 220V socket ...
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70 views

Railway overhead lines: What happens to other two phases in single phase railway power?

This is actually two questions. As my imagination I have the German/Swiss/Austrian/Norwegian/Swedish railway system on mind (15kV, 16.7Hz). I think conceptually the problem is the same on other AC ...
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90 views

Using 120 VAC 60 Hz battery charger with 50 Hz AC [closed]

I live in Australia (220-240 VAC, 50 Hz mains). On a recent trip to the United States (110-120 VAC, 60 Hz mains), I purchased some battery-powered tools that came with a charger. The charger has this ...
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1answer
61 views

Is isolation between user accessible circuits and protective earth necessary for safety?

First let me say that I understand that this question is best answered by someone familiar with relevant standards (whatever those may be). Let me give some background. When I'm designing a board at ...
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1answer
101 views

Ability of a 100km power transmission line to radiate 50Hz EM waves?

This is about confusion of relating antenna radiation theory to power lines. Assuming a straight 100km or even longer possible power transmisson line with 50Hz frequency. What can be said about the ...
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1answer
36 views

max. switching power of relay in datasheet

I want to use SPST relay to control resistive load as well as inductive load i.e. ceiling Fan (Load<150W). I used the 5VDC relay (HF46F-G) which is capable of 7A current, 250VAC. Datasheet: http:...
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1answer
75 views

tilt switch to activate power socket

I am after a way to activate a 300 W LED lamp to come on when a trampoline is jumped on and to turn off when the mat goes level again, then back on when jumped on and so forth. I was thinking tilt ...
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3answers
119 views

Switching 240VAC 1A max from 5VDC

I'm planning a device that can switch a 240VAC 1A current - most likely 0.5A but it's nice to have the head room. A relay seems the most obvious choice but given the low current it seems over the top ...
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4answers
108 views

How can I run my e-bike wheel on AC power?

I have an electric wheel designed for an electric bicycle conversion. By my understanding, the wheel is essentially a 48V, 1000w rated brushless DC motor. It comes with a thumb throttle and kill ...
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2answers
117 views

Transformer open secondary

In the circuit provided by the link, would having an open secondary coil (not having it connected to any ground) damage the it? The coil is connected to pulsed 240v ac at 50hz. If it is not arcing, (...
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1answer
45 views

PE pin position

I have one question. I'm designing a PCB which is a sort of smart switch (so, basically, you have one 230V input and one 230V output, where the output and the input share two wires, N and PE, and the ...
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1answer
30 views

Fusing on dual voltage industrial device

Please forgive me if this question has been asked before. I am designing a heating device that will be sold to industrial consumers. In our past designs we have had multiple versions of the same ...
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0answers
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Can I use a RF and/or Time-domain reflectometer to find 'wet contact'?

Friends of mine have a circuit where the RCD trips but only after prolonged rain. There are a number of garden and security lights on that circuit so I very much suspect there is a junction box where ...
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1answer
44 views

Question on Ground/Neutral connection for a 220V equipment

I sketched the following schematic from a motor controller board that has to be operated at 220V from L1 to L2. The earth wire is connected to the chassis of the machine. Where I live, it's common to ...
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Electrical safety measures in LED bulbs for the European market

Which electric safety measures are required to introduce LED bulbs on the European market? Which electric measures prevent that the plastic LED bulbs will melt down or ignite at the end of life? I ...
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Designing an inverter with its DC volt and gnd connectors as multi-pins along the PCB, how do i lay out my decoupling capacitors?

Should I distribute multiple decoupling capacitors along the connector rails? Or Should I have a few large capacitors centralised? Is there a mathematical way to evaluate this? Any other methods ...
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2answers
43 views

on a network analyzer's measurement what's the meaning of a negative PF?

on a 1 MVA transfomer, process in the place is plastics injection machinery. On the plotted data from an analyzer results in PF jumping from 0.998 to -0.997 (roughly) for all the measurement period ...
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2answers
70 views

What is the effect on kWh if the power company reduces line voltage to a residence? [closed]

We just received our power bill and it is showing a 30% rise in kWh for the past month. Nothing has changed in our home. We were even gone one full week in the month. To make it more interesting, ...
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3answers
152 views

Calculate Angle for Triac Phase Control

Triac-based phase control of the mains power into resistive load. According to this post, https://www.physicsforums.com/threads/how-to-calculate-rms-voltage-from-triac-phase-angle.572668/#post-...
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1answer
48 views

What fuse to select for a 240W power supply

I have a 12Volt 20Amp 240Watt regulated power supply to use for a table top pinball game - comprising of solenoids (2@ 12V 8A peak), some LEDs and a micro controller. The unit has an internal fuse but ...
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1answer
36 views

Rocker switch & Electronic Relay switch circuit (240v)

I have an already existing circuit between the mains wall supply and a window shutter (see image), it has a gewiss rocker switch for opening and closing the shutter when you press and hold one of the ...
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3answers
392 views

“Live neutral reverse” and “hot/neu reverse” difference?

I've got a "Meterk GFCI Electric Socket Tester" that can detect "live neutral reverse" and "hot/neu reverse" cases. Meterk E2752 What could be the difference between these cases? Isn't "live" a ...
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1answer
81 views

4 channel digital scope

I wish to view 3 phase waveforms from an alternator (DUT) through isolation transformers via a digital oscilloscope. A 4 channel oscilloscope is obviously ideal for this as I can view the waveforms as ...
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1answer
258 views

What is the purpose of a reset button on power strips?

I'm just curious why would someone put a reset button on power strips in which don't usually implement any digital circuitry. I'm sure it's not for discharging any capacitors, since power strips don't ...
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2answers
57 views

Small device to detect AC outage

I want to create a small device that detects AC outages and sounds a buzzer powered by a battery. I have some experience working with arduino and DC electronics but I have no experience in working ...
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2answers
75 views

Why do we have “live” and “neutral” wires? [duplicate]

Our house wiring is AC. I thought that AC means we have current flowing from Wire 1 to Wire 2, after 1s/Frequency it flips and current flows from wire 2 to wire 1 and this goes on and on. I heard ...
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2answers
31 views

Pros and cons of centralised vs decentralised power deliver for small devices

How does compare using one power supply for multiple devices vs each device having its own - regarding efficiency eg. power consumption? Model situation: Home automation using low power devices such ...
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1answer
48 views

Supplying relay board with mains voltage [closed]

I bought a relay board (this one) that can handle 10A at 250V, my question is: if I wire a mains supply into it, say from a ring circuit (that powers sockets throughout normal houses). Will the relay ...
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1answer
43 views

During the positive cycle of US AC MAINS Electricity is the secondary Voltage back EMF or in phase with the AC MAINS?

The Sine wave of AC Mains in the US starts at zero and increases to Vmax~169-Volts. in the beginning magnetic Flux Change is greatest as it is proportional to the slope of the AC Sine wave (which is ...
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3answers
86 views

Do 240V AC switches only need to open the active wire?

I want to add a simple inline switch to a small, mains powered lamp (~240V AC, 10W Max). It's earthed; it has a typical 3-core cable with a 3-pin plug. I bought a bunch of switches, expecting ...
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1answer
67 views

How much power do power stations in parallel supply?

In modern power systems, the power is supplied by effectively connecting multiple generators in parallel. However, not all these generators are equal, some stations supply more power than others (I ...
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3answers
129 views

Is there a practical way to create/inject some visible interference into a nearby AC mains?

I have this 230 to 6V rms step-down transformer. I use it to observe the mains voltage. But recently I needed to create some interference or spike in the mains. So I first tried the following: I ...
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1answer
95 views

60 Hz signal between thumb and forefinger? [duplicate]

I was playing around with the oscilloscope and noticed when I measure between two points on my hand, I see about a 1 V signal at about 60 Hz. Do I oscillate at 60 Hz? Does this have anything to do ...