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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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How to calculate or show in matlab/pspice the DC component from a circuit simulation?

Based on Pspice I'm simulating this RL full wave rectifier That gives the next voltage and current output at the showed probe point The idea is to extract the DC component of the current or voltage, ...
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3answers
1k views

Integrator as DC servo

I have used integrators in the feedback loop of standard inverting and noninverting amplifiers to eliminate DC off-set at the output, the circuit Im talking about is something like this simulate this ...
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2answers
18k views

Voltage Divider Supply (Unloaded and Loaded)

The loading down of a system is the process of introducing elements that will draw current from the system. The heavier the current, the greater is the loading effect. This is the the highlighted ...
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Connecting two wires to a DC 12v port on a controller board with 4 pads for a monitor

Sorry, the question was difficult to word. Basically I recently bought a controller board for a monitor and the DC cable I got wasn't correct. So until I get the right part, I just want to test the ...
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438 views

DC motor temporary speed change with simple Boost Converter

I would like to know is if it is possible to give a slight voltage change to a dc motor with simple electronic items. Meaning that the voltage would normally be a set amount (10v) but would either ...
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1answer
50 views

How to chose between 9V or 12V (or others) DC power supply [on hold]

I see a lot of devices working either with a 9V DC input or a 12V DC input, usually provided through a DC jack connector. I was wondering about advantages and/or inconvenients of both voltages. ...
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Advice for PCB layout 230V AC to 18V DC with another function (beginner continued)

I am continuing a thread Beginner's second PCB circuit design: AC to DC Does this PCB design look better than the previous and do you understand it? I also want to know if the terminal blocks ...
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5answers
3k views

Beginner's second PCB circuit design: AC to DC

I am designing an AC to DC converter and I just want to make sure that I am so far doing the right thing — placement of components and wiring etc. — as I am a beginner. Does this look ...
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5answers
1k views

Switch for DC application

I have two solar panels in series totaling a maximum of 80 VDC and 500 Watts. I believe that would be a maximum of 6.25 Amps. Could a 20A 120/277V AC switch handle that since 6.25 Amps is a ...
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1answer
130 views

Op Amp as a simple switch

I want to build a little voltage switch that switches on a buzzer and a relay when a certain voltage is reached. Please have a look at the schematic. I use a trim potentiometer to set up the switch ...
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0answers
29 views

AC/DC Converter isolation transformer, where to buy? [closed]

I have been wandering around with the thought of designing my own AC/DC step-down converter to save cost instead of buying ready step up/down converters. I need to have a small form-factor ...
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1answer
109 views

Standard 12 Volt DC fan for PC: how much AC ripple can support? Does ripple increase noise?

I want to know which is the mechanical effect to run a DC 12V brushless common fan with a very basic and poor power supply (just a diode plus a low value capacitor, no regulation at all). In principle,...
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68 views

DC Barrel - Powering a battery pack

I am looking for a DC barrel to power a battery pack. The battery in question is connected in 10S3P, that's is a nominal voltage of 36V. I am currently looking for a DC barrel that can withstand at ...
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2answers
34 views

High temperature electrical heater [on hold]

I've been trying to put together a relatively simple electrical circuit to heat an electrode to 750 degrees celsius. In theory, is it simplest to persist with using several car batteries (not those to ...
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2answers
35 views

How does the power efficiency of an appliance compare using 12V DC or 240V AC with an inverter?

With an off-grid system, if an appliance supports powering via both 12V DC and 240V AC, is there any difference with the power efficiency of either method excluding the draw of an inverter used to ...
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1answer
133 views

How to reduce noise in this circuit?

I'm using a Raspberry Pi in a circuit I'm building that includes a few elements. Elements in the circuit: PWM driver to control 3 servos Mic board for recording Class D Amplifier that drives 2x3W ...
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2answers
128 views

In an audio circuit, with an LM386 chip - how does the DC electric power and the AC audio work?

I am currently putting together a simple audio amplifier using an LM386 chip. In the midst of studying how this chip works, and the proper circuit analysis behind it, I began thinking about how ...
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1answer
124 views

What is the correct shunt size for the following ammeter and configuration?

I have the following ammeter: https://www.aliexpress.com/item/Red-led-Display-Color-0-56-Digital-Ammeter-DC-0-100A-4-wires-3-digit-car/1301822575.html The seller recommends 75mV 100A shunt be placed ...
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1answer
64 views

Current limiting a starter motor

I'm planning to try to build an electric go-kart. My idea was to use a 12V starter motor from a car to power it, since used ones are fairly cheap and easy to get. (I already have 2 of them to ...
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1answer
33 views

Linear regulator operating point over input DC Sweep analysis

I'm sweeping the linear regulator input voltage on DC using Spice from 0V to maximum expected Vin. However, as the OTA that makes part of LDO is internally supplied by the output voltage, the ...
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0answers
77 views

Way to power a monitor that requires 12 V 2.5 amps with a PC USB port [closed]

I am looking to see if there is a way to power a monitor like this: (https://www.amazon.com/gp/product/B07774L6TT/ref=ask_ql_qh_dp_hza) over one (or two) of the PC's USB ports, so theoretically it ...
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2answers
51 views

Can I run DC voltage through RJ45 Connector with Magnetics?

I am designing a PoE (Power over Ethernet) application. My question is can I run 48V DC Voltage through a standard RJ45 Jack WITH Magnetics? or do I need one WITHOUT magnetics? I am planning to use ...
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4answers
7k views

Need help on 2N3055 12v DC to 220v AC Inverter Circuit

I am about to build a 12V DC to 220V AC inverter using power transistor 2N3055. I am following this circuit diagram. The transformer is 220V to 12V step down (12-0-12) 4 Amp transformer. And the ...
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3answers
82 views

Does voltage and current have an inverse relationship in DC power transmission?

Let's suppose that we want to transmit a 1kW via DC generator with the below voltage level. From this we can see that the relationship between the DC voltage and current is inversely proportional, P ...
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5answers
187 views

Why do we use alternating current and not direct current for mains power plugs within a house? [duplicate]

I understand that for transporting electric energy it makes way more sense to have AC. But within my house, I don't think that argument holds any more. Devices I use (roughly ordered by power ...
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1answer
136 views

starter motor field coil wrapping material

In my Land rover starter motor , the field coils are wrapped in cotton tape, I see that Egyption cotton tape is sold for this purpose, but I am told I can use rubber tape, will this interfere with any ...
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1answer
133 views

Convert 0-5 V input signal to 0-100% PWM

I am attempting to speed control two aftermarket DC brushed fuel pumps in an automobile. The OEM pump control works in the following manner: When driving conditions demand a decrease in fuel supply, ...
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3answers
85 views

CCTV camera running 700 ft [closed]

I an trying to run a CCTV 5mp camera from the end of my long driveway to my DVR. Using RG59 18/2 awg 700' 12v dc. I get some voltage drop when IR LEDs turn on at night and makes the camera turn off. I ...
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0answers
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Building a LiPo battery pack for output 270v DC

so this is related to my other question if anyone wonders. I’m building out a EV battery pack to boost charge a vehicle in real time during heavy duty cycles. The vehicle currently has no external ...
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2answers
137 views

Capacitor Voltage during Transients

I am starting to learn transient analysis series RC which requires our own equations to be derived, but I don't understand how the voltage across the capacitor is given in the equation below from a ...
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28 views

Can a MTS 101 2 pin ON-OFF switch rated for VAC be used in a DC circuit?

I'm currently looking at buying a bunch of MTS 101 rocker switches which are rated for: AC 125V 6A, AC 250V 3A For DC the rating is not available http://www.massuse-relay.com/details/MTSSeries.pdf ...
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1answer
70 views

270v DC current limiting circuit

I have looked through some of the current limiting responses, but don’t see any close to what I’m working on for my project. I have an EV system running in around 200 - 270V DC. I want to build a ...
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2answers
71 views

Avoiding DC voltage drop for surveillance cameras over long distances

Trying to power 2 HD-TVI cameras 800 ft away from my home office. The wall mounted adapter provides 12v DC at 1 amp. I am looking for a good solution at the lowest possible cost. There are ...
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6answers
10k views

Why is a railway's third line or overhead line DC and not AC?

As the title states, in the rail industry, why are the majority of railway's third line or overhead line in DC volts and not AC volts? My initial guess would be that it is in AC since it is easier to ...
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0answers
45 views

DC signal detection

I have a current source that can output different types of waveform depending on the input, including DC (Howland current pump). I need to find a solution as to make sure that when DC is not required ...
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4answers
11k views

Does electrical current flow from positive to negative or negative to positive?

When you listen to people wiring up a DC circuit they seem to mumble about the electricity flowing from positive to negative. However in school I was always taught that DC electricity flowed from ...
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43 views

Input protection on a DC jack

I am designing an battery powered instrument with around 20-40Ah 3S li-ion batteries in it along with a 10A 3S(12.6v) external charger. Due to ease of availability and the current capacity I have ...
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4answers
19k views

12V DC UPS for Network Equipment

My requirement is to keep running supply of low power devices like DSL modems, etc. Most of these devices input 12V/9V DC so i don't see the value in using ordinary UPS which converts DC to AC then ...
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1answer
56 views

How do I combine 3 batteries in series and parallel with different outputs?

I'm looking to combine the 2 circuits shown in the picture below using a switch.(ON-OFF-ON) I would like to keep the 12V output seperate from the 24V output. This is to maximize efficiency when using ...
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1answer
48 views

Automatic Power Selection with MOSFET

I need a circuit which will automatically disconnect the battery from LOAD when ext. DC power is connected so that the battery won't get damaged. Theoretically a pair of diodes can solve this but ...
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0answers
60 views

What calculation can be used to predict the voltage across an air gap as a plasma spark discharges over 1ms?

I am trying to determine what voltage and instantaneous current is available if using a spark gap in air or other gas. Comparable to an auto ignition. This will be DC current. There will be a main ...
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1answer
88 views

How can I build BJT amplifier with Vin and Vout requirements (peak to peak values)

I have been working on a project but I'm not sure if I'm complying with the requirements that I was given. Design a BJT amplifier such that VIN=0.1 V and VOUT=5 V (peak to peak values). ...
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1answer
98 views

PCB Mount DC Connector /Jack

Why does this DC connector have holes at the ends of the pins?
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0answers
45 views

Thevenin Equivalent circuit, concept question

I am looking at the circuit in: Apply Thevenin Theorem to a circuit with 2 sources? The circuit and its equivalent have been given as follows in the thread: Circuit: Thevenin Equivalent: Instead ...
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2answers
192 views

How to dim my dc push button led switch that is too bright?

Attached is a screenshot of my button and the dimmer I found, it’s getting a 12V source. I figured using wiring the pwm dimmer like the one shown will work. Please let me know your suggestions on if ...
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1answer
41 views

Difficulty sourcing a 6mm dc adapter/plug/converter…any ideas?

I recently bought a second power supply for my laptop. The laptop requires a 330w power supply (it runs a desktop grade CPU), which costs around £120 (Laptop is the Asus GL702ZC). I managed to source ...
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1answer
55 views

12 Volt DC Power Supply set up

Can I connect a 12 volt DC regulated switch mode power supply (good voltage control) in parallel with a 12 volt DC car battery (great amp supply) to supply the extra current need to run my RF-...
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1answer
116 views

What type of motor is this? (photo included)

I want to make this motor work, but I can't understand what type this is. I supplied 5V DC to the terminals, but it just kept buzzing and the coils were energized. It also had some kind of circuit, ...
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1answer
68 views

converting 80Vdc to 50Vdc

I am working on a project that requires an existing power supply outputting 80VDC @ 60A to be reduced to 50VDC. Current is not really an issue in the application. Does anyone have any useful ...
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1answer
176 views

IGBT contactor design

I found this circuit in an older post. I was thinking about using this in place of a contactor to break under load. The load would be at 500V 300A DC. There would be overcurrent protection in line ...