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Questions tagged [dc]

DC stands for Direct Current, which means the flow of electric charge in a single direction. Examples of a DC source are batteries, solar panels, dynamos.

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Transmitting power over long distances via PoE vs DC cable

I need to power 15 devices in a room where there is no AC power. The devices need 5V D.C. and the peak current consumption of each device is 2A. The nearest AC outlet is atleast 50ft away and running ...
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29 views

Source Transformation

I have a question regarding the circuit below: I have to simplify the circuit using source transformation and then find the current ix. The bottom circuit of the last image is my final simplification....
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How is it possible to ever have frequency on a DC circuit?

Preface Please read this carefully. I put a lot of time into it and am genuinely attempting to understand. I've read numerous articles about DC and AC circuits and searched numerous places to get ...
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3answers
48 views

Convert Battery to AC @ same voltage

I have some LED fair lights that run on 30V @ 0.4A supplied from an AC mains supply. They have been wired to flash using some form of notification to the AC (I'm not interested in them flashing). I ...
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KCL / KVL Circuit Analysis

I have a question regarding using KCL / KVL to analyse the circuit below to find all currents and voltages. My question is : When performing KCL at the top centered node, what way should I assume ...
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43 views

Circuit design problem

You I wanted to create a circuit which contain motor for land and water.motor for water should not work in land and other motor should work.i tried to use the fact water is conductor of electricity ...
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32 views

How do I use 12 V batteries to power DC loads and charge them at the same time? [duplicate]

I need to power an air pump for fish pond aeration (not yet bought) and also led bulbs (not yet bought). I have two used, but still ok, 12 V 200 Ah flooded deep cycle batteries. I decided ...
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45 views

DC or AC electric motor? [closed]

Which is better for Electrical Vehicle conversion? An AC electrical motor or a DC electrical motor? And why?
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how to choose/design a capacitor value for surge current(for protection) for DC brush motor?

I am driving a DC BRUSH Motor at 30.V.D.C and the current is 300 Millie ampere, it is powered by L.M.317 I.C .My sir is suggesting to provide a capacitor as a protection form surge/peak current ...
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1answer
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Can identical DC power supplies with common ground produce varying voltage on same circuit?

For large installations of 5V LEDs, this PixLite page suggests using "power injection" from supplemental power supplies. Their wiring sample says: Note that the DC ground of all power supplies ...
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1answer
54 views

Opamp confusion

I would really appreciate a little help here if someone explain me why his Voltage is 4v while mine is 10/3 and one more thing: whats the point of Applying KCL at node 1 when 5v is already known at ...
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43 views

Connecting a 74LS47 to a 7 Segment Display [closed]

I am confused on how to connect the 74LS47. On the ABCD input, it came from flash ADC, just so you know. The 7 segment LEDs won't light up. I know the problem is the resistor connection from 74LS47 ...
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Can the metal body of a dc motor be used as negative terminal for that motor?

I need to power a micro DC gearmotor (6V, 0.5A), but due to the position in which it needs to be placed, i can only access the positive terminal (of that motor). It is possible however to connect the ...
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Where to place a diode - DC 12v motor controller

I'm building a controller for a DC motor. I'm using a 12V DC motor from windscreen wipers. Here is my circuit diagram and a video of the simulation I made. https://www.youtube.com/watch?v=...
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1answer
51 views

Discharging 18650 battery at constant rate

Hello I am planning to do some tests with a 18650. In these tests my goal is to measure required time to discharge them with different discharge current rates (1A, 2A, 5A and so on...) The op amp ...
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1answer
44 views

Current change through Series resistors

My question surrounds a simple scenario. I have a 12V DC power source connected to 2.2kΩ/10kΩ/22kΩ resistors in series. For an assignment, I have theoretically calculated Voltage drops across all ...
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36 views

DC motor at open load

Why at no load condition armature current is very small in DC series motor. Please explain me, what exactly no load mean. Thank you.
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DC motor induced emf in field winding

In case of DC motor even if DC voltage is applied, due to commutator an AC current flows through armature ,then due to this changing current, does any voltage is induced across the field winding? ...
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How to represent a variable DC supply potential difference on a circuit diagram

I have a circuit diagram for a physics experiment. On the diagram I have represented a variable DC supply, but I would like to know where do I write the potential difference selected on the variable ...
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1answer
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DC shunt motor rotation

ln case of dc shunt motor , how can a field winding produce rotational torque,whose field current is very small when compared to armature current. i mean how can it provide so much attraction ? ...
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52 views

Output voltage of a rectifier

Is the output DC voltage of any rectifier (Halfwave, Fullwave or bridge) simply equal to \$\sqrt{2}\$ times Phase to neutral AC input voltage? Or does every rectifier circuit have its own formula to ...
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56 views

Does a DC generator that generates at least 7.4V and 32A that weighs less than ~200g exist? [on hold]

I am doing some research on hybrid energy systems for quadcopters and trying to simulate a small engine and a generator powering a quadcopter as an alternative to batteries. I was able to measure the ...
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1answer
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What type of current is used by a transmitter? [closed]

(Short question , No need to downvote): What is the required current type in a RF transmitter (AC or DC). Since Phones have a battery (hence DC) how do they power their transmitter if AC is required?
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1answer
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AC input not matching DC output

I know this might sound stupid but it has me stumped. I am trying to calculate the average AC power input required for a few electrical devices which will be connected to a generator. The issue I'm ...
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3answers
122 views

Connecting multiple Fairy lights in parallel to single power source

The above diagram shows how I'm about the connect the LEDs, info regarding the drop forward voltage been taken from: Calculating forward voltage for a string of fairy lights: multimeter shows "1&...
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1answer
31 views

Connecting unbalanced parallel battery strings to a common DC bus

We are currently researching a system in the design phase which will use 2 parallel 48V lithium battery strings. Each string will have a battery management system ensuring the cells are balanced. ...
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5answers
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What kind of tool is used to record a voltage over time to a PC file like a waveform?

I don't have any training but am doing some hobby electronics. I would like to record a change in voltage over time, sampled at around 100+ kHz. Ideally, I'd like to record around 20-30 min of two ...
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3answers
55 views

Is it possible to use DC-restoration as a half-wave rectifier?

A simple DC-retoration circuit: seems to do the about the same job as a half-wave rectifier, is it standard to use these two circuit instead of each other ? I tried to increase the capacitance of ...
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1answer
41 views

Diode purpose on vending machine motor and switch circuit

I have a project using vending machine motors, arduino, pi etc. The motors have a NO microswitch that is ON when motor spinning and OFF when returning to the original / start point, to detect 1 full ...
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Why giving a step voltage to a DC motor doesn't show typical RL circuit behaviour?

My goal is to get an estimate of the order of magnitude of the inductance of a DC motor. To achieve this, I set up the following test circuit (L1 and R1 represent the motor, back emf is not shown): ...
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1answer
35 views

DC motor power generation

Can any one tell me If we rotate a DC motor(1800w) in its full speed how much electric power(as a generator) it will generate?
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4answers
71 views

Determine the current through a voltage source for nodal analysis

I'm struggling with a problem our professor gave us, which states: "In the following circuit, find the value of the resistor R_x so that the power consumed by the resistor R1 is the maximum." ...
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1answer
48 views

How can I tell whether a DC device will accept a greater voltage than stated? [closed]

Over the time, as an amateur, I've developed a sense that DC powered devices with internal circuitry should be fed with the voltage stated on the case. Having seen certain devices (e.g a portable USB ...
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Capacitor actual value with DC bias

I did find this answer which explained why the capacitor is affected by the DC bias, however, my question is more on the application. Let's say I have a capacitor for which I have the DC bias ...
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1answer
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What is the main difference between AC and DC generator basic working principles? [closed]

I cannot understand the main difference on AC- DC generator basic working principles. Lets consider how a loop wire works with a magnetic flux inside a DC generator briefly. Whenever the sides of the ...
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1answer
51 views

Can I safely connect 20 Raspberry Pi Zeros to this 5V 10A power adapter

I want to connect 20 Raspberry Pi Zeros (5V, .200-.300A) to a 5V 10A power supply shown below. The setup Im planning will look like the photo below but with many more Raspberry Pis. I posted my setup ...
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Can I touch voltage?

After watched this man this man, I have some questions. He touched 170 VDC, what is max DC voltage can I touch when I dry? And wet? What is max AC voltage can I touch when I dry? And wet? Is ...
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2answers
84 views

Precision resettable fuses

I am a scientist, and I have found myself needing to interface two disparate pieces of equipment. I have a precise, automatically controlled current source that I wish to interface to a very ...
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2answers
54 views

Can DC voltage on a DC relay switch an AC circuit?

Can I use a DC relay with 5VDC to switch a 120V highpowered circuit? Thanks
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73 views

Removing DC from signal

I am using the MAX30102 sensor to calculate blood oxygen concentration and I am trying to understand an algorithm I found. Some background on SpO2:https://www.nxp.com/docs/en/application-note/AN4327....
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With what can I replace power supply Foshan Hanyi S126SMD3 [duplicate]

I have an infrared sauna and it seems like the power supply is broken. I want to replace it, but it's really hard to find the original one: Foshan Hanyi S126SMD3 http://www.zidonghua.com.cn/...
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101 views

Why are there current and voltage limits in a DC bench power supply?

I have a few questions about bench power supplies. Why does a DC PSU have a low output voltage limit, usually in the range of 18V-24V? Why is there a current limit built into the PSU? My ...
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1answer
86 views

How to determine DC input voltage of a device without its charger? [closed]

Had a MotoMaster (Canadian Tire) 27/3 LED flashlight for 4 years now. Model was discontinued 2-3 years ago. Lost the charger at least 2 years ago and the light's battery FINALLY died today (!!) I ...
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1answer
65 views

Relation between Amps and Thickness of wires

I have some questions that have been bugging me for the past few days, and I am here in hope of some help. My Understanding of how battery works: "The battery (say 9V DC) does not store charge, it ...
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1answer
101 views

Why build very similar diesel-electric engines in both AC and DC traction versions?

I'm reading Wikipedia on GE Evolution Series diesel-electric engines. The series includes ES44AC and ES44DC models. Looks like they are very similar but one uses AC traction and another uses DC ...
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1answer
31 views

EHX LPB1 circuit not working

I am very new to making circuits and have tried to make an EHX LPB1 circuit: When powered and plugged in, the 9v battery overheats and all I can hear in my amplifier is static noises and no output. ...
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2answers
79 views

What resistor to choose for circuit? [duplicate]

I'm not good at physics, but I'm trying to make a lantern. So I have an LED with this characteristics: N = 3 Watt I = 0.7 Ampere U = 3.4-3.6 Volt So I connect it to 6V battery, but need ~3.5 V. ...
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2answers
35 views

Using an AC rated light switch for switching DC logic level voltage

Would it be safe and within electrical code to switch logic level DC voltage using a standard AC light switch? I know high power DC lines can create arcing with a switch of that style but low power ...
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One touch dc motor speed control

If possible, I'm looking for an electronic schematic for a simple and small method of controlling the speed of one of those small 3V hobby motors (those ones you usually get in cheap toys). The idea ...
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1answer
68 views

Can I use a capacitor which has 275v +-10% tolerance in a 9V circuit?

I am trying to get parts for a circuit i want to make and I'm very new at making circuits. As a result i'm unsure if i can use a 150nF capacitor with 275v+-10% tolerance in the following circuit or ...