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# Tag Info

## Hot answers tagged dc

50 votes
Accepted

### Can I reduce voltage from 3.3V to 1.8V using a 1.5V battery?

TL;DR; Your friend is telling you how to destroy a battery, potentially violently. Use a proper voltage regulator circuit instead. Batteries are not designed to be used a voltage regulators. While it ...
• 68.1k
49 votes
Accepted

### How do I power/wire something that is rotating constantly WITHOUT extra batteries?

You are looking for a slip ring. This is a device designed to do exactly what you describe - transmit power and/or signals to a rotating object. Generally, they work by having a rotating circular ...
• 12.3k
48 votes

### How do I power/wire something that is rotating constantly WITHOUT extra batteries?

An alternative to slip rings is the rotary transformer. This consists of two cup-shaped cores that face each other, with the windings inside the cups. If you drive the primary at a high frequency (we ...
• 176k
47 votes

### Is this an AC or DC signal?

DC + AC = DC Plainly put: No. It's AC with a DC offset, if you will. This is less about whether the sign changes (that sign is just relative to some arbitrarily defined reference), but about whether ...
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41 votes
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### Using clothesline steel core wire rope for AC and DC

Steel, having just around 10 times higher resistivity than copper means it will take ten times the conductor area to match copper. If you measured 13 meter of it to 3.8 Ω, the cross sectional area ...
• 15.7k
39 votes
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### Short circuit = no power?

You should not be so hard on your professor. Much of the confusion newcomers to EE struggle with is that we talk about theoretical IDEAL circuits as part of the teaching process. In ideal circuits ...
• 46.9k
38 votes
Accepted

### Why does inverter synchronization with the grid take 5 minutes?

It's nothing to do with synchronization. It has to do with ensuring safety of utility workers. The inverter should be quick to disconnect in the case of a grid failure (seconds) wait a period of time (...
• 410k
37 votes
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### Does this AC to DC + breadboard setup have the ability to kill/severely hurt me?

These can be good. They're usually good. You don't need to guess about quality. You only need to consider the source, and look at the markings to see if it has the mark of an NRTL (Nationally ...
36 votes

### Circuit for measuring high voltage DC voltage (up to 1000V)

A resistor divider will do what you want, but at this voltage there are some issues you can normally ignore: The top resistor has to be able to handle 1 kV. Those are harder to get than "ordinary" ...
• 314k
35 votes

### Can I reduce voltage from 3.3V to 1.8V using a 1.5V battery?

Let me show you exactly why this is a bad idea to use a battery in this manner. The following simulation shows an example with a 100mA load. As you can see this forces 100mA of current to flow in the ...
• 57.5k
32 votes
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### How come charging bricks don't work backwards?

It just doesn't work that way. It's a different operation so different hardware is required. Like how running an signal backwards through an adder won't make it subtract. The circuit itself has a ...
• 56.9k
32 votes
Accepted

### DC motor pump always transports in same direction, regardless of polarity

Some quick googling reveals that this is a membrane pump. The actual pumping action is performed by a membrane that moves up and down. The direction of the motor does not change the direction of flow ...
• 5,073
31 votes

### 5V DC over Coax

A "better" way is to send 12 V (or more) over the coax and have local regulation to 5V at each RaPi outlet. You can use cheap buck regulators available on Ebay (a few GBP or dollars) to take the 12 V ...
• 465k
31 votes
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### What is the purpose of transformers on the output side of a DC power suppply?

Transformers don't work on DC, so they're most likely common mode chokes. A common mode choke is a transformer, but turned 90° so the current flows through both coils, in opposite directions, so the ...
• 79.9k
30 votes
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### Using DC in transformers?

Transformers are AC only. Running DC through a transformer basically gives you a heater. Critically, transformers work through the fact that a change in magnetic field induces a voltage in a wire. ...
• 32.3k
30 votes
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### How can low voltage, high current (kA) power be dangerous?

The voltage for the Hall–Héroult process is inconveniently low (and the current too high) for efficient parallel operation so they use a whole bunch of cells in series. From this source ("Studies on ...
• 410k
29 votes

### Why can an AC circuit breaker not be used in DC circuits?

Direct current is more difficult to interrupt because it is continuous. Alternating current alternates polarity so it crosses zero on its own which helps to extinguish the arc produced across the ...
• 56.9k
29 votes

### Why do trolleybuses power cables use DC and not AC?

Trolleys with overhead wires often disconnect momentarily and the high inductance creates an arc of the same current that allows some continuity but with some drop of voltage or power. Whereas AC ...
• 146k
29 votes

### Using a 2 A, 48 VDC rated switch in a 8 A, 12 VDC circuit

tl; dr: nope. The switch will fail. I think you’re misinterpreting how switch ratings are derived. While the two proposals would appear to handle similar amounts of power (96W), switches are specified ...
• 55.2k
27 votes
Accepted

### Should I use AC or DC between buildings?

The voltage drop is going to outrule any 12V circuit. Rearrange the solar panel, batteries and charger as an 48V circuit. That makes a voltage drop of 1-2 volts less critical. It also brings the ...
• 14.4k
26 votes

### Is this an AC or DC signal?

It has both AC and DC components. Which of these you regard as "the signal" depends on its intent (i.e. on the information content). If it is say analogue audio with some DC in there for ...
• 1,465
25 votes

### Can I apply a 24v DC current to an analog voltmeter graduated between 8 and 16v for a few seconds?

You could use a couple of resistors to half the voltage seen by the voltmeter. You would then just need to double the reading. This would protect the voltmeter from damage. simulate this circuit &...
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25 votes
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### 1kV DC Circuit - Insulation on ground wire?

Consider this: You have your 1kV power supply, with an impressively insulated wire going out to a resistor. Coming back, you have a return wire with light insulation because, hey, it's grounded! ...
• 46.7k
25 votes
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### Designing home DC wiring

Loss at voltage conversion is just a function of how good your converter is, 5% to 20% losses could be expected at each conversion. Losses in distribution are the real killer. With 120/240 volt ...
• 170k
25 votes

### Why does the resistance of a space heater decrease as it gets hot?

Silicon carbide and similar IR heating elements are semiconductors and have a negative temperature coefficient. Image from here
• 410k
24 votes

### How can low voltage, high current (kA) power be dangerous?

The loop of conductor that carries the 10 kA current has non-zero inductance. That means a large amount of energy is stored in that loop as $\frac{1}{2}LI^2$. If there's a break in the circuit, the ...
• 170k
24 votes

### Short circuit = no power?

even touching both ends of an AAA battery with a metal wire produces sparkles and heat To analyze this circuit, you have to consider both the internal resistance of the battery and the actual ...
• 132k
24 votes
Accepted

### Why can an AC circuit breaker not be used in DC circuits?

You certainly can use Square D "QO" panels/breakers on DC And the reason you can do that is Underwriter's Laboratories (UL) listed the breakers for DC service, and the labeling and instructions (...
24 votes
Accepted

### What is causing this distortion of a pulse wave when recorded to a reel-to-reel tape?

Your original digital signal is bent out of shape because it has been high-pass filtered by the tape recorder. Let's have a look at Korg Volca service manual and dig in the schematics, here is the ...
• 79.9k
24 votes

### Why do trolleybuses power cables use DC and not AC?

From what I know, transmitting current over long(er) distances is more efficient using AC. That's true if you can step up the voltage. In the case of the trolleybus the wires are energised at the &...
• 178k

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