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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58 views

Help DC/DC 24V 400W

I have a LED LAMP, fed by a 24V 400w 17A (car/firefighter) and times to times the battery needs to be charged, so we turn on the engine and the alternator, start the job, but the problem is when this ...
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43 views

Driving car electrical vacuum pump

I am trying to drive an electrical vacuum pump from a car directly from 12 VDC. Earlier, I succeeded with a different pump just by connecting them to DC power, the other pump (different brand) used ...
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29 views

Simulating Railroad ECode track circuit from a Raspberry Pi

I'm looking to simulate a track circuit by sending out digital voltages of 2.5 volts from the raspberry pi at varying intervals of time (see image below). My question before I go too far into coding ...
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wiring usb cables for powering multiple devices via a bus terminal

Hi all, I have a created a home brew cable to power up a monitor and a raspberry pi zero, and I have blown up a capacitor on the monitor card, and I have no idea why :( First question: Why did the ...
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2answers
57 views

AC L/N connection and DC ground question

I've recently bought new power supply because I wasn't able to repair the old one. And I don't want to do something stupid. I'm trying to do the wiring now and is there any way how to figure out what ...
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54 views

Why are electric blankets AC?

You’d think electric blankets would use a 12V DC adapter to step down the 240V AC to 12V DC. It has the potential to be just as effective while also being safer. Do you think it’s because of the ...
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87 views

When power removed from LED circuit LED stays on

I have a 12v DC input that I am stepping down to 2v with 610 ohm resistor. When power is removed the light is staying on for a period of time and slowly dims. Would the resistor be acting like a ...
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2answers
29 views

How is dc restorer circuit used for PWM demodulation/detection?

In the Microelectronics Circuits textbook by Sedra & Smith, it is said that: As an application, consider a pulse signal being transmitted through a capacitively coupled or ac-coupled system. ...
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How can i control the current of 12V 30 amp dc load? [closed]

Please tell me should i use potentiometer r transistr r any other device to control dc load of 30 amp and 12 volts If transistor please specify the number
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Can we use DC-DC Buck convert installed 3.8v battery to power Phone continuously?

I have a Windows tablet whose battery is dead and I want to convert it to without battery to use as a digital photo frame. Table dead battery is 3.8V Can I use DC-DC Buck convert (DC-DC converter ...
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1answer
60 views

Identify this 19.5V DC power supply connector [closed]

Can anyone identify this HP DC power supply connector? It's not the usual 5.5mmx2.xmm barrel connector.
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3answers
62 views

How to drop 5v regular phone charger voltage to 3.7v to run a device, which use 3.7v output battery before

I have Motorola Moto 360 2st edition smartwatch and watch original battery is dead. I have converted smartwatch into table watch in DIY wooden block and added 18650 3.7v battery instead and now its ...
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Soft Close OS / Battery Switch / Improvement

I have a system that gets +12VDC from a source. The source is controlled by a switch, which I can not access. When the switch is on(close) my Raspberry Pi starts to work. (I am using a voltage ...
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99 views

Confusion about DC current through conductors

From electrostatics, we know that all the charges reside on the surface of a conductor. We also know that there is no skin effect for DC flow, which implies uniform flow of current throughout the ...
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Designing home DC wiring

I've been thinking about this for a while. Now that we have means to generating electricity in DC, what would it take to do a DC wiring for an house to work along the traditional AC wiring. ...
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RECOM Input/Output Filter Calculations

I am new to dc/dc converters and was hoping for some input from the community to see if I am on the right track. I two questions with the first being related to the data sheet EMI filters and the 2nd ...
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38 views

Start and Close Depending to Engine Status

I have an interesting question, which I really don't know how to do it or it is even possible. Problem: I want to start a computational unit (ex: raspberry pi) when the engine starts. If the engine ...
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25 views

DC to LIPO charging module reverse Feedback

I want to be able to use DC 12v to power my circuit but also have ability to have it powered by a battery. The thought I have is: * A on/off switch allows battery output to be switched on/off while ...
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DC Jack working (pavilion g7 ) [closed]

I have restored a hp pavilion g7. Establish that the laptop is not receiving power at any time, the dc jack LED is not lit. Is there security here? Have already searched a lot on google. Why do the ...
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1answer
55 views

DC amps fluctuating when measuring?

So as some background, I have a bathroom exhaust fan with a built-in Bluetooth speaker. By default, the speaker is powered only when the light is on, but my goal is to have that on all the time. The ...
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31 views

DC Current Density and Voltage in a Finite-Length Conductor

Assume you have a rectangular bar of copper with finite length L. You apply a voltage difference at two points on the top surface of the bar; (x1,y1) and (x2,y2). Because the bar is finite in length,...
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2answers
42 views

AC to DC converter device (AC adapter) with adjustable output voltage and adjustable output current [closed]

Is there a device available in the market that can take an input AC from mains and convert it into DC and output it, the output current and voltage must be adjustable. I know there are AC adapters ...
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31 views

How to identify and check if transformer is working fine?

I have 3 in 1 SMD rework station and in that Machine veriable DC power supply is not working and I am unable to check if transformer is working correctly or not and if I have to replace how to find ...
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45 views

Buffer amplifier for DC-1MHz (discrete parts)

I would like to make a buffer amplifier from discrete parts (transistors) which is working from DC to 1MHz. I'm not able to google any schematic or tutorial or app note etc. Everything I found was ...
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1answer
63 views

How can I build a circuit to drive a 12V solenoid from a 3V source, so up 3V to 12V by storing in capacitors, charge and discharge cycles?

No electronics background, noob, but I want to drive a small solenoid to cycle it everytime I push a button. I wanted to use 2 AA batteries in series as they fit the size of my project well. I will ...
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5answers
115 views

What is the purpose of the ferrite bead on DC Adaptors?

According to WikiPedia: Ferrite bead suppress high frequency noise. In the case of wall power adaptors, are they trying to protect the device being powered or are they protecting the PSU from high ...
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45 views

How to sense a small current while handling larger ones

For one of the projects I'm working on, I need to monitor a DC power line for reverse current; the solution has to output a 24V signal when around 10A or more of current is flowing in reverse through ...
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3answers
105 views

Latching Relay That Follows +12VDC Trigger and Uses No Power Unless Switching

I have an application where I have a +12VDC circuit that I need to use as a trigger for a latching relay. So, when +12VDC is present, the relay would SET. When +12VDC is not present, the relay would ...
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60 views

reversing behavior oh NC switch (for dummies)

i'm wondering if i can use a NC switch for courtesy light of my toyota, At the same time as NO switch for a device called "sterring auto tilt" when you enter the key you clik a switch that allow the ...
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1answer
74 views

DC Motor - need replacement [closed]

Ok I’m am hoping someone can help me. THREE of my 4 door locks stopped working. Dealer quotes me $500 (parts, labor, tax) or $200 (parts, tax). Quote to myself to fix FC-280ST-16200 KD603713 ...
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88 views

solving circuit using mesh equations

Im trying to solve this circuit.I think ive got something wrong because the results are a little different than what i was expecting.Any help would be very much apreciated.Ive got this so far. -20 + ...
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74 views

Determining the component values for Dc

Draw the circuit diagram for DC and determine the component value. The transistor must be biased with : This is my attempt to solve this The picture bellow is the way I drew the DC circuit diagram ...
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1answer
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Question regarding supermesh

So im trying to solve the folowing circuit using mesh analysis but i cant get the right results.Im trying to find the currents of mesh 4(down to the right) and mesh 1(left on the upperside).Ive ...
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1answer
51 views

What happens when two different voltages are connected to a car battery

I have purchase a battery charger solution that has a two part system. I am having a few problems with it which has led me to realise that the unit supplies two different voltages to the battery at ...
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1answer
45 views

Class A amplifier

So i have to make a circuit for my university, and it has to be made in electronics workbench. I tried to make a class A amp after this schematic: And made this in EWB: My problem is that my circuit ...
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2answers
65 views

Stepping up from 12vdc to 100vdc/-100vdc

I am looking to power a phone ringer circuit that requires +100 V DC and a -100 V DC. I have found a circuit here but this converts it to 120 V DC with a transformer. Is it possible to get +/-100 V DC ...
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4answers
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Half wave vs full wave rectifier [duplicate]

I know that a rectifier converts AC voltage into pulsating DC voltage. However, when would you use a half wave rectifier as opposed to a full wave rectifier ? Can you give an example of some ...
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1answer
58 views

AC line isolation on multi-level PCB design

Due to space limit I had to design the PCB in multi-level form, the top front side of the PCB is AC line and under that is DC capacitors: Is the 3mm air gap between AC line and DC capacitors enough ...
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59 views

Draw the corresponding AC circuit

I have the following transistor, whose I have calculated the parameters that were not given. Now, I want to draw the corresponding AC circuit. Can someone help me with this or give me any source ...
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Do 24-volt DC arc fault breakers exist?

I've seen arc fault breakers for 80-volt DC systems, which I understand to be a requirement for photovoltaic installations. I'm interested in whether such devices exist for 24-volt DC systems. Does ...
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1answer
79 views

AC to DC power supply - earth ground capacitance on DC output

I have a mains to 60v DV power supply that I’m using for a project. Needless to say it managed to give me a bit of a shock. This surprised me as it’s supposed to be floating. With no load the power ...
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1answer
70 views

Find voltage across inductor in RL circuit

I have this circuit in wich I try to find the voltage across the inductor (VL) at t = 0+ and the switch OPENS at t = 0 simulate this circuit – Schematic created using CircuitLab Here are my ...
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39 views

Pulsing one-way current

In EveryCircuit, they have three different voltage sources, one is DC (left), one is AC (middle), and then one is just pulsing (right) -- Is there a formal name for the 'pulsing one-way-current'? Is ...
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Copper Coil and Electromagnetic Induction

Waiting for answer Does mixing thickness of wires affect the Induction? What I mean is that I've like some 2mm and 1mm copper wires joined together. Basically I remove insulation on copper wire ends ...
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1answer
40 views

Issues encountered when adding DC adapter to light powered by battery

I have an LED light bar powered by 6 AA batteries connected in series. There is also an RF control unit to turn the light on/off. The light eats through the batteries rather quickly thus I decided to ...
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30 views

How to calculate armature current at startup of a PM DC motor?

You pick the following commercially available DC motor with permanent magnet excitation. Write a MATLAB script that simulates the transient and steady state characteristics of DC motor above. ...
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67 views

DC Wiring Color Conventions

Below is a simplified version of a system I'm working on. There's over 10 devices and they all come through the ammeter and split off into each device (only using 2 devices here for simplicity). The ...
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2answers
48 views

Wiring a 6 pin On/Off/On toggle switch (DC) 2 Pole

I bought a 2 pole 6 pin On/Off/On toggle switch that's for DC power, (25A 12V) see here: Toggle Switch The only issue is that I have no idea how to wire it, as mentioned, it has labels on the back, 1,...
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2answers
65 views

Positive and negative rail for op amp circuit

I need a positive and negative rail to power an op amp Since it's an op amp for a voltage reference, would using a circuit like this one be enough? Input voltage is unregulated 37 volts, with 4.7k ...
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87 views

Amplify AC signal only

I amplify a signal which including AC and DC.Why is the output waveform changed when C1 is 0.1u?And how to decide the value of C1?

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