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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Confirming the use of a RIFA snubbing component across 120V relay switch

I have a mains relay switch (Packard C230B 2 Pole 30 Amp Contactor 120 Volt Coil) which allows me to turn on my pre-amp based on the existence of AC voltage on the amplifiers AC output plug (which is ...
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19 views

Measurement of 230VAC relay noise

I have an MCU which is switching a load, which is connected to 230VAC via a two pole relay switching live and neutral. The load is another MCU board with its own ACDC. My problem is that when the ...
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1answer
42 views

Why is mains voltage showing up on my oscilloscope from MagSafe shield?

I'm theoretically aware of grounding issues that can come up when using an oscilloscope [e.g. as explained in this video], but I can't make sense of this one: I have a device under test (imagine an ...
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1answer
83 views

triacs from dishwasher

I have PCB from broken dishwasher and I would like to learn something from it. There are 6 smaller - STMicroelectronics Z7S, 1A triacs and one bigger STM T4 3570. My guess is (cannot verify it now) ...
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1answer
106 views

How did I manage to not be hurt after accidentally making an electric contact between mains wires?

Warning: mains is dangerous, often fatal and should not be messed with. I accidentally touched both live and neutral of a 230 AC mains via dupont wires after a shower (still wet feet). However I ...
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64 views

What needs or works better with DC than with AC electric?

Solar power is becoming more popular, and it seems a lot of people who have solar panels have a DC to AC inverter. It seems ironic to convert DC electric to AC, and then the the AC gets converted back ...
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3answers
44 views

Complex power calculation across parallel loads

I have the following problem which require the calculation of Load L3 apparent power, real power and reactive power. I have done the following as the described in the figure trying to get 2 ...
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2answers
62 views

Double the current capability of a mains socket by wiring another in parallel [closed]

I have an appliance that I know draws more or less 16A under 240VAC, but I only have 13A sockets around. Is there any off the shelf solution?
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26 views

What topologies are used for synchronization of AC power in a micro inverter?

I would like to know the design pattern utilized in syncing the AC Sine output of a micro-inverter (or inverter in general) with the grid. Please also give any good resources for designing an ...
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4answers
116 views

earth as a voltage reference

Why is the neutral point of the alternator hooked up to the earth which makes all the voltages of the lines with reference to the earth. Doesn't this makes us more risky to the shocks? I think we use ...
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2answers
69 views

Mixing two or more AC sources to handle overload

Can I mix two or more AC sources to handle overload and maintain a stable voltage of 230V AC? For example if power from solar panel cannot handle a heavy load can I mix power from different source ...
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3answers
88 views

Fast 220v AC power failure detection

I'm building an AC-Detection circuit. I want to detect when the AC power has failed ASAP so that I can react very quickly. (like 1-3ms should be enough time) This was my first idea. It works in ...
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1answer
36 views

How is this ELCB connected to earth?

I have bought an ELCB and a mini DB board for a small solar/inverter project. My understanding is that an ELCB trips when there is a potential difference between earth and neutral. The diagrams I've ...
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499 views

Is the design decision for different frequencies in PAL and NTSC related to the AC mains power frequency?

In discussion a friend mentioned: In the original implementation of PAL and NTSC they used the AC current as a means providing the frequency for the TV. As the different mains had different ...
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2answers
79 views

will i damage this toy motor by running it on a higher voltage? [closed]

I have a hand held shaver that is chargeable. the socket plug for the device says 02A250V- and the green battery inside the device looks like this: and the ...
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2answers
96 views

How much ground current vs. neutral wire current?

This is a follow-on question to an earlier question of mine; I think it deserves its own question, though. I am trying to learn as much as I can about how current in a power grid (transmission and ...
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2answers
79 views

Understanding ground current

I am trying to understand ground current in a power distribution system. The basics, of course, are simple: in the power grid, the "hot" wires carry high voltage, while the return path (the neutral ...
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0answers
24 views

Type M AC Adapter Pins -Identification Help

Below is the picture from a Belkin Wemo wireless switch teardown for the side that plugs into the wall outlet. The complete teardown is here They have mounted the AC pluggable pins directly on the ...
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1answer
68 views

Correctly Using ACS712 hooked to a microcontroller

I am making a project that involves AC current measurement from the Mains. I have done a bit of research and have found that the ACS712 can do this. I would like to know the correct way of using ...
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2answers
80 views

Power demand beyond maximum deliverable power

simulate this circuit – Schematic created using CircuitLab We got an elementary dc power system as shown in the figure. The maximum transferable power P_max is 0.5W. Is it possible to ...
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2answers
80 views

Simple surge protection circuit for incandescent bulbs

A friend of mine is having a large, fancy / artistic lamp at home (Europe) and uses a "500W incandescent bulbs on 230V" as recommended by the manufacturer (link). His problem : every month or so the ...
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1answer
48 views

cheap usb hubs passing on mains voltages

So we've heard a lot of sensational stories about people dying from cheap mains->5V USB converters. What sort of corners do these manufacturers cut and do they even save much money than if they made a ...
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1answer
62 views

What is the purpose of an inductor on an incoming AC line?

I am trying to build the following schematic. It is a AC/DC converter from Cui link I do not understand the function of L2. What is its purpose? I am having a ...
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2answers
83 views

Oscilloscope Output with its positive terminal touching human's body and negative terminal left open

it once happened that when I touched the positive terminal of the Oscilloscope input probes letting its negative terminal open, I observed sinusoidal voltage signals with 0.5V peak to peak and of ...
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1answer
121 views

Wired vs SMD resistor on 230V optocoupler input

For circuits similar to the one below, we used large wire resistors with proper power rating in our past designs. The question came up, if it would be a good idea to replace the resistor with SMD ...
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2answers
84 views

resistive braking for induction motor?

It occurred to me that since single-phase AC induction motors can act as generators, it might be possible to brake an induction motor with a resistive load. The basic idea is that when you want to ...
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2answers
107 views

Looking for a simple way to inject a signal on 60Hz Mains line

Okay, so I'd like to be able to inject a really simple signal on top of the 60Hz AC Mains. It doesn't have to contain any data per se, just a simple signal to trigger a receiver on the same ...
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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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2answers
95 views

Arduino Dimmer Shield Schematics Interpretation

I've read so much about Thyristors, Triacs and Rectifiers on the last days that I'm almost understanding my schematic, but I'm not there yet - I need some help. Overview: I'm making a home automation ...
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2answers
127 views

Question on Mains return current

Since the neutral wire is grounded at the circuit breaker panel, I am confused as to whether current actually flows along the neutral back to the service head? If not, then what actually absorbs the ...
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2answers
76 views

unexpected power supply behavior

I am using this large 24V power brick (rated for 9.2A) to power a small circuit (an arduino controlling some RGB LED strip, drawing less than 0.5A). If I physically pull the plug out of the wall, the ...
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2answers
82 views

Differentiate between mains and a generator

This question is related to: Can I differentiate between a UPS, Generator and Main sine wave using a micro-controller? I'm only interested in the difference between mains and the generator. ...
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31 views

What's the typical harmonic distortion on the secondary side of a distribution substation?

What's the typical harmonic distortion and waveform found at the low-voltage side of an urban substation (I.e: the aggregate of appliances and secondary distribution system impedance)?. If you can ...
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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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201 views

Need circuit to Switch 240v a.c. mains with 3v or 5v

I have the IRFP460 power transistor which if I understand correctly can switch 20A/500V on 20v input. I am wondering what a circuit design would look like that would allow me to either (a) switch ...
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2answers
115 views

Plugging in an oscilloscope in a land of non-grounded outlets

Background: I have only one outlet in my house that remotely approximates a proper equipment grounding conductor (it's bonded to the mains ground point via the armor of 50s vintage AC, which is better ...
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3answers
145 views

Resistor calculation

I'm still new to electronics and I am trying to do a calculation. Say I have a 100 Watt bulb that runs at 120V and my source is 240V. I know the bulb will blow but my question is: if I wanted to put a ...
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591 views

Multimeter into wall sockets

If you placed one of the multimeter's probes into the hot slot of the wall outlet and touched the other probe to your skin while grounded, for example to some dirt outside, would you get bitten by the ...
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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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2answers
238 views

If a large AC generator is overloaded, will it lose frequency or voltage?

If a large AC synchronous generator, like one from a hydro dam, were to receive overdemand from the grid, would it start losing frequency or losing voltage? I know they have several safeguards to ...
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2answers
163 views

Turn a mains light on slowly

I've been looking at creating a simple circuit to slowly turn a halogen daylight bulb on over about 30 minutes as soon as power is supplied to simulate dawn. I've got a 240VAC 42W halogen bulb that ...
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3answers
138 views

Is the white wire carrying any electrons

I don't understand why neutral in 110v , does it carry any current ,does the load like the light reduce the current
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1answer
146 views

Is it possible to connect a UPS in parallel with the mains?

Short version: When a UPS is plugged in to the mains, is it possible to plug the UPS output back to the same mains? Will that work as an emergency power backup for the mains circuit? Longer version: ...
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39 views

Fan needs full power to spin up; would then like to have to run off a speed control

Fan in question: http://www.amazon.com/Active-Air-inch-In-Line-Fan/dp/B002JQ4N92 Fan speed control: http://www.amazon.com/Lutron-DVWFSQ-FH-WH-Single-Pole-3-Way-Control/dp/B000MAVHTG The lowest ...
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2answers
66 views

Is it safe to connect battery in series with wall adapter?

Is it safe to connect a battery in series to wall via adapter? I have an AC adapter which gives me 10 vDC from the wall (220 volts). I've measured the adapter and it outputs 10 vDC. I have a 3 volt ...
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2answers
102 views

Can I power a 230VAC fan with 220VAC?

Here's the fan I want to use: http://www.nmbtc.com/pdf/acfans/4715ms.pdf The 220VAC model costs $70 while the 230VAC model costs $17. Can I safely use the 230VAC model in China, where the mains ...
3
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1answer
64 views

Making conducted EMI measurements in the presence of building-wide ground-fault protection for personnel?

As is documented here among other places, the Line Impedance Stabilization Networks used to make measurements of conducted EMI as per CISPR 22, FCC Part 15, and suchnot contain large line-to-ground ...
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4answers
154 views

Providing house wall switches with 3.3v/5V supply?

It's a bit non-technical, but I'd love to hear the opinions of the pros. I'm trying to figure out what is the best way to connect my home's wall switches (lights, etc.) to 3.3V/5V. The plan is the ...
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2answers
471 views

How can a light dimmer in series modulate a load?

Not after a full breakdown of how this specific light dimmer works, but rather how a device in series can control a load. A light dimmer has the following wiring diagram. As you can see, the light ...
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125 views

Inverter using battery even when mains power supply is on [closed]

All the points connected to the inverter are using battery power even when mains power supply is on. When inverter is turned off , those points connected with the inverter have no power, not even ...