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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Does USB always supply 5.0V

I was wondering about this part of a circuit diagram. I believe the component marked as JP12 is a DC barrel connector, which I thought had three pins. One to detect input, one with V+ and one with ...
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1answer
63 views

Does order matter when it comes to AC power?

Is there anything about electricity or the electrical design of AC power strips that dictates in what order the devices should be plugged in? When I say, "in what order", I am referring to the ...
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1answer
45 views

Is there a rightside up when plugging in an AC to DC power converter? [on hold]

When plugging an AC to DC converter into an AC outlet, does it make any difference at all if the wall wort is "upside down" or "rightside up"? Is there anything about the electrical design that would ...
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0answers
35 views

how can i design a simple circuit that can be use to charge a DC(12v) using AC of 220-240V [on hold]

pls I have an SLA battery of 12V I want to connect an AC of 220-240v to charge the battery. what are the processes?
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2answers
69 views

Very High speed response AC coupling

my goal is to achieve a HIGH SPEED RESPONSE AC COUPLING, as I want to totally get rid of the DC component even though its changing rapidly I have a signal coming from a sensor ( a proximity probe), ...
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2answers
45 views

Wiring up a AAA power toy to Pinball lighting supply

I'm trying to wire up a toy powered by AAA batteries (3vdc @ .09A) to the lighting circuit on a pinball machine (6vac @ 4A) and I was wondering what the best possible solution that I can keep small. I ...
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1answer
44 views

How to controlle a motor with arduino

I have 2 og those 12v motor and a 12v battery http://www.enigmaindustries.com/Motors/Bosch_EV_Warrior.htm I want to know what s the best solution to controle the motor with an arduino Uno. Is the ...
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2answers
53 views

How do I reduce the Counter EMF?

I hope I can explain what I am asking. We will connect a DC motor to a single phase rectifier. Motor will carry a load. And motor sould be able to spin right and left. And when it is changing its ...
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2answers
47 views

Close loop circuit vs an open one in regards to an electrical bicycle light system

From what I know about DC current, for it to flow you need 2 points with different voltage (while AC doesn't flow from point to point), this why DC batteries discharge overtime, when not used, because ...
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1answer
45 views

Thevenin equivalent of simple circuit

I'm stuck on a problem and I don't know how to proceed. I have a circuit that consists of a 10μF capacitor connected in series with a variable resistor (100kΩ, 200kΩ, 300kΩ). I'm supposed to draw the ...
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1answer
34 views

LED DC Voltage Level Indicator

I am wanting an at a glance indicator of what voltage level is being supplied by a DC generator (think pedal power). My general thought is a series of LEDs that light up in sequence as the input ...
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2answers
43 views

Is it possible to have a charging unit and output unit connected to a battery at the same time?

I am very new to DIY and electronics stuff, so please excuse myself having little knowledge about this stuff. Here is what I am trying to do: Assuming I have both things (The Converter with USB ...
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1answer
50 views

DC Motor circuit polarised 2 directions switches

I'm totally new to electronicS and do not understand a lot and I've read other posts but people seem to be asking different things to me so apologies in advance if this has been covered but I've typed ...
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3answers
49 views

DC circuit theory: Equivalent resistance help

In the given DC circuit, I need to calculate resistance \$R_{2}\$: if the equivalent resistance between nodes 1 and 2 is \$R_{e}=100 ohm\$ I get the value \$R_{2}=36.36ohm\$ \$R_{1}\$ and ...
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1answer
34 views

controllable and accurate static charge generator

ive been doing some research on methods to generated static charge. ive come across 3 main methods: wimshurst generator, van der graaf (and Negative Ion Generator). wimshurst and van der graf seem ...
6
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4answers
384 views

How to know exact Decoupling Capacitor values for supply voltages?

When designing circuits using various components such as IC's a lot of the time the data sheets give you an example schematic where they will usually give you some values for decoupling Capacitors. I ...
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1answer
28 views

AC alternative for DC diode short-circuit protection

I have two sensors (represented in the schematic below by a switch) connected to a light. If one of the sensors trips, I would like the light to switch on. The sensors and light are directly on AC, ...
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3answers
42 views

CLL(Capacitor long life)capacitor filtering to reduce the current spikes

if we are using capacitor between the coomutation segments of brush dc moto then it reduces spark generation. as main function of commutation system is to reverse the current in the coil. by using ...
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0answers
18 views

How does Mean Well LDD range DC-DC constant current drivers handle dimming?

Mean Well LDD range DC-DC, constant current buck drivers have dimming function. 5v PWM signal allows you to dim the LEDs. Without PWM, you get the full rated current output. Now knowing anything ...
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3answers
87 views

Function generator as a DC power supply

I'm wanting to start my own lab at home so that I can learn things faster than uni teaches (we're not allowed into labs unless we're in our own lab). A friend said that I'd be better off getting a ...
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2answers
113 views

Help with DC circuit theory problem

I need help with this DC circuit problem: When the switch is open, voltage between points A and B is 2V. When the switch is closed, through variable resistor \$R_{p}\$ flows maximum current, and ...
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1answer
35 views

How to use a single supply with an opamp to create a DC amplifier

I have a single positive power supply, and I want to amplify a DC input signal. All sources I have seen decouple the input voltage with a capacitor because the input voltage is biased at VCC/2, ...
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2answers
65 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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1answer
46 views

Difference in Metal Film and Carbon Film

Hey all I have a WS2812B RGB LED strip that I am wanting to use with an Arduino. The directions HERE state that it's best to use a Capacitor and register in order to have smooth operation. So I went ...
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1answer
42 views

DC Adapter marked “9VDCX2”, what is the X2?

I have a keyboard that needs a 9v power supply. I've found one home that is marked as 9V DCX2. What does/can the "X2" mean after DC? It literally says "9VDCX2" Extra info: The adapter was originally ...
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1answer
52 views

Which end of a barrel connector is positive

I am having trouble understanding barrel connectors. From what I read online either the inside or the outside can be positive or negative depending on the direction of the current. SO which end is ...
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0answers
21 views

Steady state operation of a DC machine

Why inductance of the coil is not taken into account in a DC generator even though initially an alternating current is produced in the coil?
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3answers
90 views

Removing flickering of LED lightning

I am trying to install recessed, dimmable LED lightning in the living room. We're talking about an end solution of maybe 15-20 spot lights. My home has 120V/60Hz. Currently I am experimenting with a ...
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1answer
56 views

How to turn-on laptop's battery pack after replacing cells? [closed]

After a few years of use, my battery pack finally died. The laptop doesn't even detect or try to charge the pack anymore. So I replaced the cells in the pack for new ones, but that didn't make it to ...
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0answers
41 views

Does DC Ground Need to Be Stepped Down?

I'm pretty new to electronics and I have just a quick question about ground DC connections. If I have a device that is being stepped down from 12V DC to 5V DC does the ground wire need to be stepped ...
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1answer
98 views

How to add a DC bias?

I have 70Vrms sine wave, I rectified it with full wave rectifier. So the output is 100Vp.I will divide it down to 1V using voltage divider (0-100V to 0-1V). How could I add a 1.4V DC bias to the ...
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1answer
48 views

High Voltage MOSFET Controller - Random Failure

I have a 120V DC Motor that I need to control the speed of. I am doing this through a High Voltage PNP transistor (MJW21193) rated at 250V and 16A with a peak of 30A as I understand it from the data ...
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2answers
84 views

DC non invasive power measurment

For one of my PhD project I have to measure power consumption from different electric wheelchairs during various tasks and recor these measurment for later studies. I have not much experience in ...
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2answers
89 views

Taking an unstable DC voltage, and stabilizing it

I have a DC motor generator (basically the motor spins, and it powers an LED at the moment), and the output current (mA range) and voltage is very unstable. For an entire circuit to run on the ...
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0answers
30 views

ATX Dell PSU to Offical ATX 2.0 spec pinout [migrated]

Hey all I am using an old Dell Precision R5400 which has the 750w hot swap-able power supply. Problem being, since its a dell, the ATX pin layout is different than that of a normal, standard ATX 2.0 ...
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1answer
70 views

DC motor speed control: 12VDC 700mA fan motor powered by 7.2Ah sealed lead-acid battery

I am using a 7.2 Ampere-hour Sealed Lead Acid Battery to power a 12V DC motor which is driving a fan, and I need to understand ...
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1answer
56 views

floating ground for AC and DC power supplies

I wanted to connect two power supplies, one is AC (240V , 6A) and the other is DC (3,3V, 300mA). But i read in some referrence that connecting AC and DC power supplies could be dangerous if the two ...
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3answers
80 views

Panel mount DC barrel jack on PCB

Is it possible to solder the panel mounted DC connector shown in the image below on to a PCB? I was unable to find an Eagle library for the same. If it is not possible to solder on to a PCB, any ideas ...
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1answer
56 views

Dual Dc regulated voltage circuit design

I'm working on my term project which is designing a dual DC regulated voltage that gives a DC voltage between +or-ve 3 to +or-ve 15. I have completed the testing for positive DC output part, but I ...
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0answers
30 views

What polarity is represented by the black with white stripe on DC power cable? [duplicate]

I have a 12V DC adapter that is bricked I want to change it, and I don't know the polarity, this is the photo: What polarity represents the black with white stripe cable?
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1answer
110 views

Transformerless power Supply - 24VDC, 120V AC and 230V AC

I want to know if it is possible to design a power supply for a circuit that can operate from DC and AC using the same input terminals. Thus, the output should be xxV DC (5-24 or whatever is decided ...
0
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1answer
35 views

no-load DC output voltage of DC wall-wart circuit

I have this question and I believe the answer is 12.73 from the equation V(N) = V(Rated) * sqrt(2). Is this the correct formula and can someone show me how we arrive at it if it is. I am unsure ...
2
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1answer
76 views

Meaning of AC15, DC1, AC1, and DC13 in relay durability curves

In the datasheet of the relay OMRO G7SA from the durability curve they specify the number of operations as a function of the contact current. Each curve is for a specific current and voltage. The ...
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0answers
33 views

connecting AC signal 250V to DC signal 3V3

I want to measure an AC and DC current about 250V for AC and 3V3 for DC, i want to use an LT1787 (High Side Current Sense Amplifiers) with amplier stage and DSP to acquire the value. The problem is ...
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1answer
49 views

BJT Circuits at DC, base current calculation

I'm trying to walk through the example calculations in the attached example however I cant understand how the author gets the expression for the first step in the process. I tried making up the ...
3
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1answer
155 views

Is there a way of dividing 2 DC voltages? ie Vout = V1/V2

I need to take the ratio of two filter outputs as part of a project. I converted them to DC voltage values using a rectifier and a smoothing capacitor thinking that this would make division easier. ...
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1answer
41 views

Help solving a 2nd-order RLC circuit

This is the practice problem 8.9 of Fundamentals of Electric Circuits 5th Edition. Can someone help me with this question? I need a more detailed solution of this problem. Especially, what are the ...
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0answers
26 views

Mesh analysis confusion — resistor polarity

I used mesh analysis to find Vo in the figure below. However, my set of equations just end up cancelling each other when I do the math. I am also not sure if the polarity of the resistors changes ...
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1answer
50 views

Using an AC speed controllet with an rectifier and dc motor

I salvaged a 12 amp motor from an AC lawnmower and wanted to use a motor controller to reduce the speed. This is the controller I used http://www.amazon.com/gp/aw/d/B00GMBYFRK. The motor is a dc ...
6
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5answers
663 views

Why pulsed DC passes through a capacitor?

OK, the current flowing through a capacitor equals C*dV/dt, I'm aware of that. What I don't understand is the physics of the process: why does a capacitor pass pulsed DC (0-10V for example) when ...