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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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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59 views

How to come up with -5v DC & -12v DC for ATX PSU [on hold]

This maybe a known answer to many but this is the first time I have ran into an issue where i needed to make a -5vdc / -12vdc connection. I am speaking of the ATX power supply connections: Notice ...
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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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39 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 ...
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1answer
29 views

wrong DC jack on a laptop [closed]

I broke the DC jack connector of my laptop (satellite C850). I bought a new one but it seems it is not the good one. The original cable is on the left. see above : the two cables However the two ...
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1answer
30 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 ...
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1answer
37 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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28 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
30 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
136 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
30 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
22 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
34 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 ...
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5answers
632 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 ...
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1answer
56 views

AC-DC Adaptor flashes on & off

i have bought an ac-dc adaptor to power my mini-water pump. When i give power to the pump it start & goes off immediately and it's repeating like that till i plug it off. Adaptors LED is also ...
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1answer
46 views

How to find places to add power indicator light in simple DC circuits?

I build a lot of little hobby circuits and I usually place them inside of some kind of project box. Right now I'm working on the "Atari Punk Consol" by Forrest Mimms. It looks like this: I tried ...
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1answer
89 views

How design a circuit to control a switch?

I would like to know how I can design a circuit that can control the switch in the diagram below? Output of the circuit should provide TTL operant to open close the switch that control a 12 V DC.
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27 views

Controlling Linear Actuators

I have two 24in linear actuators (http://www.progressiveautomations.com/linear-actuator) that run at different speeds when I connect them in parallel to a 12V battery. How can I get them to run at ...
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2answers
40 views

Problem generating square wave using IC555

I'm having trouble trying to build this circuit: (Step 5) - (diagram below). I built it, and everything works fine, but the coil doesn't spark. I then used a scope-meter to check, and there is a ...
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1answer
47 views

Scale 5-15V to 30-50V using op amp

I have a sensor that output signal values 5-15V. I wish to translate the given signal using op amp to 30-50V. Can u help me with the values of resistors and circuit diagram which shows sensor as well. ...
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0answers
57 views

Charge pump configuration

Can anyone please explain the charge pump config. in this circuit. I am having a hard time figuring out what the diodes are used for, and I am not sure I fully understand the caps config. either. ...
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38 views

Circuit Analysis - simplify circuit to calculate current

I have to calculate the current i in this circuit (the values of the resistences are in Siemens, not in Ohms) Using the equivalence between a voltage source in parallel with a resistor with only a ...
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1answer
71 views

Non-inverting op-amp with DC offset

I'm trying to amplify an AC wave (from an audio input) with a maximum amplitude of about 1.8v to a DC oscillation between 0V and 5V with the centre (what would be the zero-crossing on the input) at ...
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1answer
60 views

Is this SSR design recommended?

I want a hard power switch for some battery-powered BLDC motors, but the currents (5A, up to 20A transients) and voltages (up to 60V) limit the kinds of switches I can use. Because I want some small ...
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3answers
114 views

Single-supply DC amplifier circuit with “gain” of 0.66?

I have a DC voltage source \$V_{in}\$ which slowly varies in the range 2.5…4.8V. I need to linearly scale it down by ⅔, to feed into a 3.3V ADC pin. For a voltage divider, the source has too high ...
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2answers
77 views

Passive voltage drop from 6V DC to 5V DC for 3W circuit

I plan to put an Arduino onboard of my hub-generator powered bicycle circuitry. Currently, I have a circuit consisting of: 6V/3W AC hub generator (variable frequency and power); Rectifier bridge; ...
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1answer
42 views

How to wire this component (-4dB audio)

Getting frustrated because I don't understand what this -4dB thing is in the circuit and I can't figure out how to wire it correctly or even if I have the right part. I have a 3.5mm mono audio jack ...
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3answers
96 views

Why is DC Voltage called Direct Current ?

I have had this question since a long time, and didn't find any other place to ask this. So thought will just ask here. The "DC" in DC Voltage/Supplies stands for Direct Current. So why is it ...
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2answers
73 views

How to add ground to DC circuit?

I'm just a dabbler in electronic circuits and I'm really still kind of a noob. I am working on a project called the "Atari Punk Console" (Originally known as the "Stepped Tone Generator") but there ...
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1answer
83 views

Canon no longer makes CanoScan 8800F AC adapters, help needed to replicate its functionality

The CanoScan 8800F uses a proprietary 32VDC AC adapter that's no longer manufactured. A Flickr user did the trial and error to find out how to modify another 32VDC AC adapter for use with the 8800f. ...
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2answers
53 views

Charging a bank of lead-acid batteries in paralel

I have a lead-acid battery similar to the one in the picture (mine is 15Ah) and I also have a spare car battery (50Ah). Is it safe, or a good idea to put them both in paralel to achieve a bigger ...
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1answer
44 views

6w 12v 5a peltier only drawing 1a, I am supplying more current but its only drawing 1 amp?

I just bought the peltier and its of 60 watt 12v 5a and its maximum capacity is of 90 watt power. I am using my Pc power supply which have ability to provide 12v and 15a maximum. I connect to that ...
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2answers
79 views

Question about LDOs and the practicality of this application

I'll try and keep this as organized as possible so everyone can understand my thought process as easy as possible. I will be using a 12V 5A switching power supply (available on eBay) to convert my ...
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1answer
39 views

Determining DC gain of single supply op-amp (no AC component)

I'm building a homebrew PIC programmer, and want to support devices with varying Vpp voltages, so I'm using the DAC output of a PIC16F1825. But the PIC is supplied with a +5V Vdd, so that's the ...
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1answer
54 views

DC offset spike?

A week or so ago, I accidentally damaged one of the speakers of my audio system, most probably because of a loud and high-pitched distortion (noise? - it's basically a "pop" when ...
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63 views

How to implement an adjustable DC offset removal with single supply?

I want to make a circuit where I receive very weak badly shaped constant frequency pulses with DC offsets and obtain an ultimate output with adjustable pulse amplitudes, and with adjustable dc offset ...
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0answers
29 views

How to implement a variable offset voltage in a single supply non-inverting Op-amp? [duplicate]

I want to add or remove some DC offset from the output of single supply non-inverting Op-amp. When I connect the inverting input to a voltage source(instead of GND) lets say V volts, the output has -V ...
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1answer
57 views

How do I build a DC time out circuit that stays off until power is toggled?

My girlfriend bought an LED faucet that is actuated when you turn the water on and is powered by a battery pack of 4 AA batteries (2 wire out). However, when the water is turned off, the slope of ...
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3answers
997 views

Can a diode effectively regulate a supply voltage?

I have a 6V DC battery that's rated at 2A. My microcontroller uses 5V supply at about 50 mA. I've been told I shouldn't worry about the current since the microcontroller will just take what it needs. ...
0
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1answer
57 views

Possible to take 110 down to safe level to run LEDs?

I'm working on a lamp project that I found online. It's a DIY lamp with a whiskey bottle for the base. The project itself just uses a standard 110V plug that goes right in to the wall, but I wanted to ...
0
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1answer
65 views

Transformerless rectification is giving out AC component [duplicate]

I want to convert 240V AC 50hz to 12V DC without transformer.I want the output (12V) to drive 25 white LEDs.The circuit is giving an output of ~14V DC.But the problem is that it is also giving out ...
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44 views

DC Motor Speed Control With 555

Can you please explain why this circut is not working in simulation. I get GMIN Stepping failed, too many iterations errors. Is there something wrong with the design?
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2answers
74 views

N-Channel MOSFET as 12 VDC switch

A little background: I have a 12 VDC "cigarette" socket in my car which is a non-switched circuit (so, always on). I'm in need of a switched socket, whereby power is cut when the car is not running. ...
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1answer
50 views

Is Deuterium arc lamp a AC or DC light source?

I have created a prototype photo-detector circuit to use in spectroscopy. The micro-controller code take 120 A/D readings and then returns average. I have noticed that when I use visible light ...
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0answers
27 views

Is the armature resistance of a DC motor the sum of the resistance of each winding?

I am aware of a number of methods of measuring the armature resistance of a DC motor including locking the rotor, giving a fraction of the rated voltage, measuring the current and calculating the ...
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2answers
27 views

Frequency design parameter for DC signals

I have been using some online tools to design a circuit to amplify photo-diode current. I have understood that all such tools needs a frequency/bandwidth to drive the calculations. For example, a Low ...
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1answer
43 views

Replacing a Piezo with a button

In my senior engineering design class for high school, my teacher bought a toaster oven and microcontroller and tasked my group to make surface mount digital dice kit for him to teach surface mount ...
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1answer
55 views

How to supply 5 to 12v amplifier LM386

I started electronics recently and I'm trying to make the most basic mp3 amplifier. First I tried to make the amp myself with reused electronic parts but I didn't succeed... Amplify speaker with 9v ...
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1answer
101 views

Non-zero output from a LM741 in a differential configuration

I'm trying to amplify a DC voltage coming from a strain cell (with a built in Wheatstone bridge). The voltage swings from -1mV to about 4mV depending on the strain. I've set up a differential ...
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6answers
89 views

Frequency DC voltage

Maybe it is a silly question, but a microcontroller it is powered up with a voltage of 3.3 DC voltage, and we all know that the frequency of the DC voltage is 0 Hz. Suppose that i want to generate a ...