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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What value of resistor is needed to limit current to 0.5 ampere in a 12V DC circuit?

I have a 12V DC motor that uses 1 ampere from a 12V battery. I want to limit it to 0.5 ampere because it runs too fast on 1 ampere. I know that I can achieve that by adding a resistor but the question ...
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Bridge purpose in connecting the two functional circuit [closed]

Anyone generous enough explain the function/purpose on connection between the first pin of each R12 - R22 interposed by a low C ? on https://www.eevblog.com/forum/projects/5-transistor-esr-meter-...
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How to measure a DC motor's inertia

I want to measure the inertia of a DC motor. However, I have no idea how to measure or calculate this. I need the inertia to determine the numeric transfer function for voltage to angular velocity. ...
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37 views

DC power supply exceeding current limit without load [closed]

I am attempting to create an induction heater for soldering purposes. The build involves a 24V/20A power supply, two 12 volt fans in parallel, a time delay relay and a ZVS board. I have fried multiple ...
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2 answers
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Select PSU for 12V DC water pump

So I bought me this cheap 12V DC water pump for a garden project. Then I used a wall-wart type switchable PSU (similar to this one) to do a quick test. Works, but it has problems: The pump is rated ...
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2 answers
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How does my AC adapter take 100-240V without a physical switch [closed]

I was checking if the AC adapter on my notebook could take both 110V/60Hz and 220V/50Hz (it can). The AC adapter has no physical switch to select the input AC voltage. That got me thinking, how is ...
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1 answer
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Heat Problem with MOSFET Controlling a DC Shunt Motor

EDIT: This problem is solved. To anyone reading this after the fact, let it be a lesson in making sure that your equipment actually works as intended. I'm a physics undergrad, not an engineer, so ...
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1 vote
2 answers
45 views

Difference between application of series and parallel (grounded) capacitor

I wanted to understand the difference of the two applications shown in the picture below, one is in parallel (grounded) which, as far as I know, is used as a bypass capacitor used to remove the high ...
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2 votes
2 answers
52 views

Control AC load via relay with DC trigger?

The headlight of my motorcycle is AC powered via stator. I want to switch between Hi/Low beam using a single pole double throw (SPDT) NC relay. Power to pin 30 (AC) Ground to pin 85 (?) Trigger to pin ...
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2 votes
0 answers
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Can the output of an L298N be smoothed using a capacitor to reduce buzzing?

I'm running some model trains with a Raspberry Pi using L298N modules to control motor speed. Traditionally, this would be done using what is essentially a DC motor speed controller, but I need ...
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-1 votes
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Why armature of a DC shunt generator is being rotated?

I saw the diagram of DC shunt generator and I observed that at first residual magnetism induces a small e.m.f in the armature winding and because of this a small current is produced and this current ...
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2 answers
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Best method of isolating devices

I have a 12 V DC motor whose direction is controlled by reversing polarity. I have a simple mechanical switching system that provides that function. I have added an inexpensive wireless remote control ...
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1 vote
1 answer
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Optimizing Peltier water cooler set up

Application 20 gallon aquarium cooler Ambient temp: ~22C Tank target temp: ~17C Tank houses an axolotl and needs to be kept at cooler temperatures then currently in the basement. Current Peltier Set ...
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1 answer
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Design calculations for LVDC grid

I'm looking to use 60 V to create a small LVDC grid to power up some small loads - 12/24/48 V maximum. For the purpose of this question I will assume 12 V only loads. 60 VDC will be the power supplied ...
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-2 votes
2 answers
68 views

What is the current across the resistor given in the figure? [closed]

The circuit is short circuit across the the resistor. What will be the current flow across the 30 ohm resistor?
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4 votes
4 answers
459 views

Relation between collector current and Vce voltage in saturation mode

I have confusion regarding how collector current affects the voltage across collector to emitter in NPN transistor (2N4123). How do I interpret this graph? Can I say when collector current increases ...
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6 votes
2 answers
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Maximum DC power available over specific distances from source

I'm working on a small LVDC project using 60 VDC to distribute power over varying distances to varying loads such as network equipment. I decided to work out the maths and see exactly how much power I ...
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3 answers
65 views

Transistor Not Entering in Cutoff region

I have made these circuits (DTL or TTL). And I want to enter these transistors (T1, T2, T3) in the cutoff region. But I am not able to do so. Which parameter I have to change so these transistors ...
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-1 votes
1 answer
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Highest Efficiency/Lowest resulting heat from a DC/DC conversion

I have a 336VDC power source - it's a pretty unique piece of kit and won't be changing it. I'm looking to power around 500W of equipment from it at 48VDC. However, I'm looking to do this using a DC/DC ...
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18 votes
3 answers
4k views

Does this AC to DC + breadboard setup have the ability to kill/severely hurt me?

I'm currently building a PC peripheral that uses an AC to DC converter to power a set of DC fans. I'm not a trained EE or electrician, so I want to make sure I'm not putting myself a risk with this ...
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-4 votes
3 answers
143 views

Cannot amplify DC voltage using op-amps

I am trying to amplify a DC voltage scaled from 5-10V to another DC voltage with maximum 12V. Why I am not using just a DC voltage with that value? Because the input DC is variable according to some ...
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5 votes
3 answers
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Negative DC wire gauge

I would like to mount some external flood-lights on a motorhome with a 12V DC system. I may need to install new positive wires to make sure they are sufficiently thick. I wonder if I also need to ...
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1 vote
3 answers
90 views

Power loss and voltage drop for a parallel wiring system

I'm looking to power a 50W load approximately 140m away using 48V DC. At the far end I will use a DC-DC converter to convert this to 12VDC where it will power a small DC powered network switch I have. ...
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0 votes
2 answers
117 views

Safety of a polarized DC breaker between the battery and the inverter

DC breakers use a magnet to blow the arc into the quenching channel. If the current is flowing in the wrong directly, the arc is pulled into the guts of the breaker and can cause the arc to be ...
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0 votes
1 answer
89 views

Substantial voltage drop when connecting battery to DC load

I wanted to test the battery from an e-bike. I have noticed quite strange behavior. The first thing I did was to measure the voltage. It was 66.1V which is fine for a 60V battery. When I connect the ...
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0 votes
2 answers
73 views

Two different DC motors

I tried two different electric motors with one adapter. Both are 12 V but the current and power ratings are different, and one motor takes all the current. What should I do? Can you come up with a ...
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1 vote
1 answer
61 views

Reduce or filter DC spike and noise

Goodmorning, I have a small voltage drop (about 20-25 mV, DC) on a sense resistor (0.180 Ohm) and I need to amplify this with an op-amp to reach 2-3 V (DC). The signal is not clean and the noise, with ...
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2 votes
3 answers
110 views

Vending machine motor: simple DC motor with microswitch, one revolution

Long story short, I'm currently trying to understand and control a DC motor with connected microswitch, which gives back one-revolution feedback (don't know how). I tried connecting INA219 current ...
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1 vote
1 answer
57 views

Mimic a thermistor/variable resistance signal using PWM

I am looking for a way to create a variable resistance signal to mimic the signal that would typically be provided by a thermistor, but by using a digital signal that switches to ground. I currently ...
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0 votes
1 answer
65 views

Converging Electric Fields on Metal Plate

I have a question, but I'm not a trained engineer, just curious. So bear with me on my explanation. Let's say I have a metal plate. I have DC power supply and I connect the positive electrode on one ...
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1 vote
5 answers
239 views

If two devices both require 12V 2A power can I use a 12V 4A power supply to power them both?

The question title says it all really: I have two devices that both require a 12V 2A power supply, so I'm assuming that I can I just use a single 12V 4A power supply to power them both? I'm also ...
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0 votes
1 answer
44 views

Connecting two DC-DC 0-200V SSRs in series

I want to switch a 400V DC inductive load. I am unable to find 0-400V DC to DC switching SSR. Can I use two DC to DC SSR of 0-200V in series to achieve the goal?
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1 vote
1 answer
144 views

Portable AC power source earthing?

I have an 12V to 230V inverter in my car but get confused about ground it. The inverter is centre-tapped, means live-earth voltage is +115V, neutral-earth voltage is -115V, this gives an L-N voltage ...
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0 votes
2 answers
68 views

A couple of questions about transformers

1: I accidentally supplied 9v to a 4.5v - 0 - 4.5v transformer like this: And it was working for a about a second and then it stopped and isnt working. Have i killed it? 2: Can you use a square wave ...
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0 votes
0 answers
36 views

Solar Charging EV

I am willing to connect my PV directly to my EV, without using an Inverter (losses). There will be an MPPT controller in between. RAV4 EV regular cable connection is J1772. The car also have a CHaDeMo ...
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0 votes
2 answers
55 views

bi-directional motor using SPDT relay and diodes

I have a bi-directional motor that I am trying to control using an SPDT relay. It is only working in one direction when I remove the circuit for the opposite direction, and it is either shorting or ...
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0 votes
2 answers
70 views

Feasibility of humidity controlled minifan

I am thinking of constructing a DC operated minifan out of a humistor. I looked up some sources that says humistors typically operate on AC. Is there any way of making this work on DC input?
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1 vote
2 answers
120 views

Limit 12VDC motor to momentary run time

My latest project involves running a 12VDC motor very, very briefly via a momentary DPDT switch that I have wired to reverse polarity depending on which direction the switch is thrown. In the end I ...
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0 votes
3 answers
147 views

Biasing of an NMOS transistor

I want a current of 100mA to flow through a transistor. For that, I polarize it with a voltage divider. The transistor I use is the BS270. According to its data sheet, for a current of 100 mA to flow, ...
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0 votes
3 answers
82 views

DC motor as a generator [closed]

I was wondering if I could use a simple DC motor to power a small LED and how fast I would need to spin it to do so. I am making a small air-powered engine in school and I kind of want to connect it ...
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1 vote
1 answer
99 views

Insulation monitoring device for electric vehicle

Good day to all! I am planning on designing an electric vehicle architecture from scratch. My main DC bus voltage is 400 V. However, I have got different voltages in my system. I have got a 600/400 V ...
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-1 votes
2 answers
91 views

Feasibility of 30MW DC transmission over 400m?

We have an electric motor final load of 10-30MW, in an isolated industrial location. The power source could be (Li-ion) battery packs, where each pack outputs 1500VDC, ~500A. Having 10-30 of these ...
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1 vote
0 answers
67 views

Problem connecting two DC-DC converters in one circuit

I'm building an audio mixer for microphones, and have a problem with the power supply part. I'm designing this board to work with several voltages which are +/-15V, 5V, and 48V (for phantom power). I ...
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0 votes
3 answers
179 views

Will a 4.5V - 0 - 4.5V transformer work with a 9V battery?

I am concerned as to whether my circuit will work or not before I build it (I am concerned about the battery voltage.) This is what I have but my transformer is 4.5V - 0 - 4.5V. Is there any way I ...
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0 votes
3 answers
76 views

Help find a usb to ac cord [closed]

I've been looking every where for a cord that is powered by usb with an ac outlet on the other side so I can plug the usb into a portable battery and have an ac outlet can someone please tell me where ...
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1 vote
2 answers
137 views

Is there a way to make a DC to low voltage AC circuit

All the circuits I see online are like 12v DC -> 220v AC or something along those lines but I'm only looking for something like 9v DC to 9v AC. Is this possible?
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1 vote
1 answer
34 views

Difference AC signal and small signal / DC Signal and Operation Point

What is exactly the difference between an ac signal and a small signal? Or analogue between a dc signal and operation point. I've understood ac signal as a signal with a frequency > 0 Hz and dc as ...
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1 vote
1 answer
62 views

Load testing using a resistor bank

I have a bespoke 48V down converter that I'm looking to test which should be able to provide a maximum of 500W of power. I'm looking to test the device under various loads - from 50W to 500W. I'm ...
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0 votes
4 answers
163 views

Very confused about where "ground" is connected

I actually don't know that much about electronics, but I'm very interested in learning more. I watch Ben Eater on YouTube, and whenever he needs to connect the part of a chip to ground, he connects it ...
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0 votes
1 answer
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How does the voltage change from DC to AC in capacitor//resistor circuit?

I was asked to calculate the expression for the voltage for this circuit in DC at the essential node $$v_o(t)$$ From the input voltage $$v_i(t) = A\sin(wt)$$ I did it for DC with nodal analysis over ...
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