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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A question on PWM frequency of a DC motor

I'm planning to pwm-control four of the following motors by a single ArduinoUno: http://uk.rs-online.com/web/p/axial-fans/8179151/ For some reason the nearest pwm frequency I can set is 31kHz. The ...
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2answers
22 views

connecting a hp laptop charger adapter three wire output to a two wire cable [on hold]

My laptop charger adapter broke and I a have this other old adaptor in the house. They both have the same voltage(19V) and 1.58A. The first adapter(The one that broke) has three wires (black, white, ...
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2answers
60 views

Use of 230VAC overcurrent protection for 24VDC circuits [on hold]

Is it right to use 230VAC overcurrent protection for 24VDC circuits? Why? Why not? For example: http://www.tme.eu/en/details/a9f05120/circuit-breakers/schneider-electric/ I saw some machines which ...
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1answer
43 views

Help wiring DC motor

first post here. I'm wiring a DC motor and horn that will go into a small boat I built. I would like to get some help to see if I'm doing this correctly. -DC motor hooked to a 12v battery (Max draw ...
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2answers
42 views

Am I correctly concluding that these two AC/DC adapters are interchangeable [duplicate]

I'm in the US with 120V mains. I have a "heavy" style AC/DC adapter (weighs a pound or so) and a lighter one (weighs a couple of ounces) which came off a 1TB Seagate NAS. Can I replace the heavy one ...
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34 views

Potentiometer controlled current regulation

new one here. Thing is this; I have an electromagnet (or a solenoid as I prefer to call it). When it gets energized the plunger inside is pushed out to a certain length (goes back to its original ...
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54 views

High Voltage and Turning Positive to Negative [closed]

I have +10kV DC coming off a transformer and would like to find a way to turn that into -10kV DC. So far most of the schematics I've found only deal wit up to 24V. Thoughts? Thank you in advance
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84 views

wirelessly remote-controlled DC power supply with variable voltage

I need a remote-controlled (wireless) power supply, outputting between 0 and 10 volts and 0 and 2 amps, preferably DC. It should take 110v/120v AC as input. Its voltage should be controllable with a ...
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2answers
44 views

Current in Buck Converter

In Buck Converter, when switch in ON, Vi(I/P voltage)=Vl(inductor Voltage)+Vo(O/P voltage)when we switch it On, current increases linearly(according to the wikipedia) then Vl=Ldi/dt=constant and Vo(=...
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77 views

How to fade or delay a DC Signal to remove speaker “thump”/“click”/“pop” from transistor switch?

I'm trying to create a digital audio switch or relay using an Arduino nano. It's a very simple circuit, it's just a gate (transistor) which is operated by a digital signal (computer) through a ...
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64 views

Is the resistance in a DC Motor constant if the voltage is?

Is resistance in a DC motor constant if both the load and voltage are constant as well?
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67 views

General question about Capacitor sizes in DC circuits

A general question -- let's say there is a DC circuit with a capacitor that needs to be replaced. Can I use any capacitor that is at least as large or do I have to use one that is exactly like the ...
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2answers
87 views

Using a multimeter to see if ground is connected

I've been diagnosing a problem with a relay on my car. One of the pins in the socket that the relay goes into controls the ground for the throw of the relay. When the car's computer wants the relay ...
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4answers
106 views

Motor control using potentiometer characteristics

I am trying to control a dc motor using potentiometer(armature control). Increase in voltage leads to increase in speed of motor. Even though this seems in accordance with general understanding, but i ...
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1answer
71 views

If a load is placed onto a DC motor, will the current increase? [duplicate]

When a load, such as a weight on string, is placed into a motors axle, will this cause the current to increase?
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1answer
65 views

Ground my body to DC (USB) [closed]

Does grounding body to DC power source makes sense, to get rid of any electrostatic(?) charges from my skin/body ? In my new house, when I'm standing on the floor, connect voltage meter (AC) and ...
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1answer
72 views

Using an AC drill motor with DC?

I have this motor from drill that is powered from AC. Is possible to use the motor with DC current?
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66 views

Understanding AC to DC conversion

I am able to see following specs on my laptop adaptor. 65 W Input AC: 100 - 240 V, ~1.5 A, 50 - 60 Hz Output DC: 19.5 V, 3.34 A My HP laptop: I am bit unclear ...
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2answers
88 views

Can I connect pin 11 of TL084 to ground? I mean, are there the consequences?

I wonder if it is possible to connect pin 11 of a TL084 to ground to avoid having two sources. I need to compare two signals: Signal 1: This is a DC 9V source. (this goes to + terminal of Opamp) ...
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1answer
57 views

ACS712 Low Current Sensor

Before I begin, just to let you know that I'm new to electrical engineering, in case that my question sound weird to you, but here's my problem. I bought few days ago ACS712 Low Current Sensor and ...
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1answer
21 views

DC consumption translation to AC consumption

I've a battery charger that can output 9v and 2.5A and I use full power from it that is 22.5W. Can I translate this power consumption from DC to AC current? My AC is 220V 50Hz, so I'll consume 22....
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49 views

DC Bus for Solar Charge Controller Battery

I am just learning the set up for a back up power. I am just wondering whether the DC output from the charge controller or the battery can be used for multiple loads. For example, I want to power my ...
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2answers
76 views

Small DC motor Heating up!

I am just trying to build a small fan to keep my Mac a little cooler from outside. So I have this little Box Design I made. Now, I'm a total noob at this thing so I need beginner level help here. I've ...
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1answer
45 views

Multiple DC Voltage sources in parallel

I'm building an alarm system (paradox EVO192 with ZX8 extension modules) and was hoping to have separate sections of the system each powered by it's own battery backed up power supply (something like ...
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2answers
89 views

Connecting a battery powered circuit to the earh ground [closed]

In the following circuit what would be the effect of tying a circuit to the ground from the -2V rail ? I know that no current would flow to the ground since there is no closed loop formed, but ...
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43 views

Electric latch for math toys

Please fix my tags. I'm making a series of interactive puzzles for use in classrooms. One of them is an equation graphing. It will have a grid of screws stuck into wood, with the axis drawn on. ...
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1answer
47 views

Bridge circuit and the error caused by a differential amplifier

I am currently struggeling with solving the following problem: The circuit below shows a bridge circuit, where the differential voltage between the branches is measured by a differential amplifier. I ...
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1answer
48 views

Control USB powered light with PWM, would it work?

A few weeks ago, I asked about controlling a DC powered LED lamp using PWM here, I was told that if I can get a LED lamp that uses an external DC adapter to power up, I can use a MOSFET and control it ...
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1answer
66 views

Op-amp voltage divider

I have troubles understanding the way the circuit below is solved. I figured out that the solution is: $$ V_+=\frac{R_2}{R_1+R_2}V_1 \\ V_a=\frac{R_3+R_4}{R_4}V_+ $$ But what is actually the reason ...
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Why are DC signals bad for loud speakers?

I googled and found out through some forum that: DC has a constant amplitude which overheats and destroys the voice coil of the speaker. Could someone clarify if this answer is complete and ...
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1answer
45 views

connecting the negative positive terminals of two dc to dc converter

I require two voltages for my device 22 and -20 is it possible to use two dc to dc converter to generate the two voltage and connect the negative and positive output terminals, and that will be my ...
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1answer
76 views

Decreasing Voltage of Power Supply via voltage regulator without using input/output capacitors

I have a HP laptop power supply 18.5V/3.5A that I intend to connect directly to LM7812 or LM7805 voltage regulator when I need to drop the voltage to 12V/5V. Since the laptop power supply (which is ...
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2answers
59 views

Why is DC used in circuit devices? [duplicate]

Why do circuits mostly run on a DC current? I understand that electric motors use AC but things like my laptop operate on DC. Are there another advantages to AC current that made it the standard ...
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45 views

Input impedance of audio amplifier, unclear from datasheet

I have a AN7190NK audio power IC. It is a amplifier for the car radio. I want to know it's input impedance. In datasheet it states that: Input impedance ZI VIN = ± 0.3 VDC 28 kOhm I don't really ...
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3answers
155 views

Op-Amp Circuit add/subtract voltages

I am currently struggeling with the following problem. I need to find an amplifier circuit which implements the following equation: $$ U_a=U_1+2U_2-2U_3 $$ I decided to go with the circuit shown ...
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53 views

Question about multimeter resolution

So i got a multimeter from a friend for free. This is the one: Multimeter Info In the manual of the multimeter it says that the lowest resolution of DC Voltage is 0.1 mV. does that mean that i can ...
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208 views

Why can't I vary the speed of a dc motor with only a potentiometer?

I made a simple circuit with a 9 volt battery, a dc motor, and a potentiometer. The positive of the battery is connected to one side of the potentiometer and the negative to the other. One side of the ...
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1answer
55 views

How to do DC Analysis for a Common Source Biasing Circuit using NMOS

I am having a lot of trouble with this specific problem. I want to find Vg, Vd, Vs, and Id for this specific common source biasing circuit that has an NMOS. I have these values given: Vdd = 9V, k/2 = ...
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92 views

Circuit for voltage division and DC shift doesn't work

I've connected the circuit below on a breadboard and tested it in the lab: Components: \$R_{1}=1\,M\Omega,\;R_{2}=40\,k\Omega,\;R_{3}=R_{4}=R_{5}=R_{7}=R_{8}=20\,k\Omega,\;R_{6}=49.9\,k\Omega\...
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45 views

finding the sinusoidal values of a complex current or voltage

I am having some trouble understanding this type of transformation. The materials provided by my professor doesn't even mention the method that is being used to switch from complex to sinusoidal and ...
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2answers
80 views

How “slow” is a Class T “slow blow” fuse?

I have a DC inverter that's rated for 3kw sustained with a 6kw peak (for up to 5 seconds). Per the Inverter manual, the manufacturer recommends a battery fuse rated for "at least 350 amps". How can ...
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1answer
69 views

How do I calculate Watts for a dual rail power supply?

If I have a 5V power supply powering a circuit which is connected to 0V, to calculate power usage I would take the total current in Amps and multiply by 5V. However, my current circuit uses -12V, +...
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75 views

DC Motor Speed Control Board

I have a 120VAC DC motor speed controller (diagram attached as picture) it works very well, however in the circuit there is a 5000K POTENTIOMETER that controls the actual speed/voltage - The ...
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4answers
93 views

Using a battery charger instead of a battery?

I have built a simple circuit with two diodes that light up intermittently. It requires 9V DC voltage to run. I don't have a DC source at home, and would like to avoid buying 9V batteries repeatedly ...
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125 views

Why does an uncharged capacitor short out a resistor in a basic DC circuit?

I’ve really only dealt with two laws thus far concerning circuits and capacitors: $$V=IR$$ $$Q=CV$$ The first obviously being Ohm’s law and the second the equation for a capacitor’s charge. I’ve seen ...
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65 views

DC/AC coupling in an oscilloscope

I would like to know when it's suitable to use AC coupling and when it's not in general? When using an oscilloscope, I want to know in general when it's better to use DC coupling over AC coupling ...
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76 views

Measuring DC current with Hall Effect sensor over PIC on the same circuit

Before I begin with my question just so you know I'm not very familiar with electrical engineering so please forgive if I ask some dumb question :) What I want is to know if I can use Hall Effect ...
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58 views

Permanent magnet DC motor earth wire

I have just inherited a piece of equipment that is powered by a 12V DC permanent magnet motor. My hope is to drive it using an Arduino PWM and a H-Bridge to manage the current requirements (7.3A ...