This tag refers to alternating current mains power. It usually applies to voltages with >100V RMS, but can also be used for ex. 24V industrial AC power.

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76 views

Why are these Vias of Different Shapes

While looking at how other circuits bring AC mains into their circuits, I came across this design where there are 3 differently shaped vias (from top to bottom): Figure of ...
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1answer
58 views

Current flow in AC vs DC

If a live wire is taken from AC and connected to a bulb, while the other terminal of the bulb is connected to ground, the bulb glows; but if I take the positive terminal of a battery (DC source) ...
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2answers
46 views

How to make a duplex 7 segment display

I have built the circuit below and have been using a 7 segment display which is meant to be designed to work with the circuit. However there is no clear diagrams showing which wire on the display ...
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3answers
47 views

Making my own kotatsu

I want to make my own kotatsu (a small table with an heating element underneath) and I'm considering using a "heat lamp" as the heat source (one of those aimed at reptiles, fits in a normal light bulb ...
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1answer
38 views

Will a tvs diode help my relay with inductive loads?

I am not an EE, so please be gentle! I will obviously get a certified EE to review my design before anyone else touches this so please assume that I know enough to at least be safe with 120VAC and am ...
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1answer
48 views

What is ground on a circuit that uses AC?

Below is a circuit diagram for a circuit that runs off AC voltage. Where do I connect all of the points that connect to ground? Do I just connect them all on the same rail of a piece of Vero board? ...
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1answer
60 views

Powering a Digital Alarm Clock with AC

I have built a digital alarm clock using an LM8560 chip. I tried powering the circuit with DC and the 7 segment display lights up, but none of the buttons worked and the numbers on the 7 segment ...
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1answer
56 views

Why can we drop the Omega term in Euler's expression of AC signal?

I know that for an AC signal like $$V=V_p\cos(\omega t+ \phi)$$ we can simplify it to $$Re(V_p e^{j(\omega t+\phi)})$$ But why can we further simplify it by dropping the Omega term $$Re(V_p ...
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2answers
93 views

Can I solder back together a single broken copper winding wire in an electric washing machine motor? [closed]

Can I solder back together a single broken copper winding wire in an electric washing machine motor? This is the motor: ...
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3answers
235 views

LED bulb still emits light when turned off

I have recently purchased an IKEA LED bulb with G9 fittings, to replace a halogen one. This one. The bulb is installed in a lamp with 3 other halogen G9s in a 3 + 1 configuration with a 3-state ...
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1answer
21 views

Si8519 AC Current Sensor usage

I'm trying to find a good and practical current sensor and I found this: Si8519 http://www.silabs.com/Support%20Documents/TechnicalDocs/Si85xx.pdf My idea is monitor AC Mains current, so this Si8519 ...
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0answers
39 views

In the following circuit (in the image), find the current through Z2?

The underlined symbol means it's a complex number. Es are voltage sources. Js are current sources. Zs are impedances. I don't know how to deal with current sources while solving circuit So please ...
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2answers
77 views

Measuring Electron Beam Currents

When it comes to measuring electron beam currents with a Faraday Cup (or any that will pick up electrons and act as an anode), primarily AC and transient signals, my understanding is that one can (1) ...
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1answer
57 views

Why should I use DC coupling when I'm finding the frequency response of a circuit?

In my last electrical measurements lab I was asked to plot the frequency response of several different filters (high pass, low pass, and band pass) using an oscilloscope. My professor told the class ...
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2answers
102 views

Can a tank circuit store energy for a simple AC system?

If you take the circuit below, with the switch closed, assuming the Tank circuit is tuned to resonate at the same frequency as the source, then I would expect the tank to become charged, and the ...
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3answers
63 views

Can I use a switch rated as 250VAC 25A to switch 50VDC 25A?

I am looking for a switch that can handle 25A continous current, the voltage will be maximum 50VDC, most often about 46VDC, and it will be used to switch on two dc-dc converters that have no load ...
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1answer
31 views

OR switch for bathroom radio

Imagine there are two rooms. Room 1 has a light bulb and a switch to turn in on/off, and room 2 as well has a light bulb and a switch to turn it on/off. What I want to do is - connect a radio player ...
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2answers
80 views

Why do AC motors have various back EMF shapes?

I just saw in one of the threads that apparently, a permanent magnet synchronous motor and a brushless DC motor have different back EMF shapes. But why? I thought those two were exactly the same in ...
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4answers
2k views

Does AC Power have Polarity?

When I run 24VAC into a full wave bridge rectifier followed by a 220uF electrolytic capacitor to turn it into ~32VDC, the source has two wires. Does it matter in what order I connect the AC wires to ...
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2answers
54 views

Using DPST Relay to control AC Load

Below is the functional schematic that I am planning to use to control an AC load (air conditioner in this example with max current draw of 32A). Since I am still relatively new to mains power and ...
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2answers
86 views

How do I design a current transformer?

I want to make a Current transformer using toroidal ferrites to measure 220/50-60Hz AC current(40A max). Is it possible? And how can I calculate secondary turns count? Ferrite properties: H = 2000, ...
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1answer
106 views

Why there are live and neutral wires attached to house's wall sockets

If AC voltage is alternative, why there are two (Suppose there is no earth wire) wires attached to the wall socket: live or hot, neutral wires? And I think that in small home generators there is no ...
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0answers
21 views

How can I control an IR204E in a PK543A to remotely operate this apartment door buzzer? (What relay do I need?)

My apartment door 'suite station' (buzzer) is a TekTone IR204E (pdf). It has an option for talk, listen, and open door. It contains four wires labeled 1, 2, 3, and X. My research leads me to believe ...
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0answers
60 views

How to control a bulb operating on 230v using a switch operated at 5v

Hello Electrical engineering community, Maybe this is an easy question to answer but I am new to this so definitely need assistance. I want to control a bulb which is driven via 230v AC mains using ...
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0answers
73 views

Circuit for finding engine RPM using the magneto's coil ground wire

I'm looking to see if there's a solution without using a microcontroller to find the engine RPM (perhaps spark frequency is a better term?) using only the magneto's coil grounding wire. This wire ...
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1answer
42 views

How can I use the presence or non-presence of an 120VAC input to actively discharge a bias power rail?

I'm designing a power supply that has an input of 100VAC to 300VAC. On the primary side on the main transformer, I have a 15V rail to power the control chip (a FAN6920) and a gate drive chip (a ...
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3answers
97 views

Is Faraday's Law not working?

Faraday-Lenz's law was easy when I was in 12th standard. But it became more complex when I jumped to Engineering. Recently when I was studying about inductors and how they oppose changes in currents, ...
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1answer
51 views

Operation of a Growler to test armature shorts

Can someone explain to me how a Growler for testing electric motor armatures works please? I have obviously read the Wikipedia Growler page but it is still foggy. So the growler unit acts as the ...
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1answer
36 views

What is the name of the IC that runs a low-harmonic power supply?

I'm interested in building an AC/DC converter for low-harmonic applications. Single-phase AC input, followed by a rectifier and a PWM-controlled boost converter. I know there are ICs which are ...
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1answer
93 views

Charger light circuit [duplicate]

I have a charger light. It gets charged by 220V AC supply. It can light 5 LEDs. I know that it needs to make the supply 220V AC to DC of lower voltage nearly 5V to 10V. Then it can charge the small ...
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1answer
56 views

Is there a limit of series connected LEDs when driving them with AC?

I want to drive as many as possible LEDs with AC grid voltage. Assuming that there are \$n\$ LEDs connected in series, the voltage drop on the will be \$2.2nV\$. Then the voltage on the capacitor ...
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3answers
72 views

Can I use this relay for DC

http://www.dx.com/fr/p/ssr-25da-25a-solid-state-relay-white-134494#.VDmPWPl_uap It says AC output but how can this transform DC to AC ? Shouldn't this act like a switch ? If my circuit is DC and I ...
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3answers
95 views

Effect of non-inverting op amp on the AC and DC components of the input

I was wondering what the effect of an op amp like the one in the image below is for an input signal such as \$0.5\sin(2000\pi t) + 0.5\$ V? Are the DC and AC components amplified with the same gain? ...
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2answers
254 views

Understanding cause of arcing in AC filter circuit

I have an induction hot-plate that one day blew a fuse in my distribution panel when plugging it in. (With the obligatory smoke from the device of course) On visual inspection, only the AC filter ...
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2answers
149 views

Can I use DC resistor in 220 V AC circuit?

Can I use DC resistors as AC resistor? If yes, is there any problem interfacing with it? Please recommend AC resistors for working with 220 V AC 50 Hz.
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3answers
86 views

How and why is a magnetic field transmitted with alternating current?

I apologize for the basic question (or if it is incorrect in its assumptions,) but how does one account for magnetism in alternating current? If I generate alternating current to a motor, why do my ...
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0answers
68 views

How to create a 120V-175V Variable Frequency Generator

I am dealing with a system that requires me to drive a capacitive load at 120V-175Vrms, AC square/sine wave at two frequencies: 50Hz and 2000 Hz @ Ipeak = 100mA. I am currently trying to find the best ...
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1answer
69 views

AC source in parallel with resistor problem [closed]

For an AC source of for example +-12 V, can a connected resistor at any instant, have 24 V across it? Because my textbook has a problem in it involving such a source and says (hint: consider the ...
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2answers
105 views

Controlling AC mains using Arduino and removing control easily

I am planning to for an Arduino to read status of a switch, and accordingly switch on and off AC appliance, for a demo purpose. I want to add a feature to it of easy recovery to manual switch control. ...
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1answer
59 views

AC switch & power supply reverse engineering

Below is schematic of self-powered(by passing little current not enough to operate) switch reverse-engineered from PCB. simulate this circuit – Schematic created using CircuitLab Zener ...
0
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1answer
108 views

Detect alternating current using one contact only and arduino analog input

I am trying to setup an arduino so it can detect an AC where it only has access to one pole. (kind of like these "electricians screwdrivers" that you put in one of the connections of an electric ...
0
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1answer
153 views

How to replace bulb with LED in a PWM circuit (car)?

I want to replace a light bulb in a Peugeot 308 SW with a LED. The bulb works (lights) normally, but the LED blinks. I thought they are controlling the bulb in alternative current but my digital ...
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2answers
67 views

Wheel speed from Shimano dyamo hub using arduino

I'm trying to figure out a way to extrapolate wheel speed from the Dynamo hub I just purchased. I outputs 6V 3W AC, and I would like to potentially measure it using an arduino if possible, I' assuming ...
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2answers
58 views

Actual/theoretical benefits of round or flat outlet prongs

What might be the reasoning for European connectors having rounded prongs while USA and UK connectors are primarily flat pronged? Please correct any mis-tagging.
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0answers
68 views

High voltage low voltage switching circuit

I am working on a project which involves switching of a point from AC mains to low voltage ground when I start my low voltage circuit. Till now have come up with following circui. 1) Point A in the ...
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1answer
29 views

Replacing an AC power supply that is 2 volts higher than the original but has the same current rating [duplicate]

I have an audio mixer that requires an AC 16 volt 1 amp external power adapter. I need to know if an 18 volt 1 amp AC external power adapter would work without damaging the audio mixer?
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0answers
48 views

Total current through a parallel ac circuit

I want to calculate total current entering the circuit in this question (10.15). Please help me with this and I would be obliged if someone give a detailed explanation on this because I guess simple ...
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6answers
2k views

What makes mains voltage safe in homes?

When I started learning about electrical engineering, one of the most important safety guidelines that I learned was that voltages over 36V can be dangerous. As my circuits professor put it, 120VAC ...
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1answer
52 views

Equivalent sequence/stepper relay to “FINDER - 20.21.9.012.4000”

I am currently looking at this relay: FINDER - 20.21.9.012.4000. Which is step relay, that makes contact AC output active with coil input DC (12V) [which i need]; and disconnects output when coil is ...
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4answers
2k views

What are the highest DC and AC voltages or currents that can be considered as safe?

By safe I mean safe for us when we touch a wire that is not insulated. I have heard that human body resistance is normally 50k Ohm when dry and 20K Ohm when wet. Therefore, these voltages or currents ...