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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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Does an automotive DC generator care about battery voltage? [migrated]

Can a 6 volt positive ground generator be used in a 12 volt negative ground system? The question pertains to converting a 6 volt positive ground automobile to a 12 volt negative ground system. The ...
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2answers
166 views

Why do engineers usually short ground and negative ports on a DC power supply?

I'm fairly new to electrical engineering, and have seen many DC power supplies where someone has shorted the ground (green) port with the negative (black) port. From my understanding, the ground is ...
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28 views

DC Voltage Multiplier for Positive and Negative Input

I have a small DC motor being driven by a controller which supplies +6V/-6V to the motor to control its speed and direction (elliptical machine resistance control motor). The issue is that 6Vs is not ...
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3answers
86 views

Simple Non-Inverting Op-Amp Problem

I am trying to double the voltage out from a 1.5V battery using an MCP618 op-amp as a learning experience prior to using the op-amp to amplify the output from a set of strain gauges set up in a ...
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2answers
46 views

Op Amp Output Voltage

I have a question about an LM741 op amp IC. I am using the op amp as an comparator (open loop with no feedback), as seen below: When the op amp output is low, the output voltage is still around 1.2v....
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16 views

How to apply Thevenin's theorem in multivoltage(3) sources?

Here is a question I am not able to tackle as the requirement is to solve it by Thevenin's theorem. The question is to find the value of current passing through 20 ohm. I can perform Mesh analysis ...
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1answer
31 views

DC-Link capacitors sizing for 3 phase inverter, which is feeding BLDC motor [on hold]

I would like to ask about an estimate for inverter DC link capacitors, where this inverter will supply 48V 20A 3phase Brushless DC motor and it's driven using a 5 kHz PWM.
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4answers
62 views

Multiple Buck Converters

I have multiple buck converters, model XL4005 (datasheet ), fed from a 12V battery source to several devices i.e. My motors (require 12V), Arduino (requires 5V) and Transmitter module (require 3.3V). ...
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3answers
134 views

Building AC to DC circuit that can not be run on a breadboard

First I have an AC power source. Can I solder the power source directly to a rectifier to make it DC? I plan on using a protoboard using the DC power but I need the board to be able to handle 2Amps ...
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1answer
15 views

Solar Panels: Charge Batteries via MPPT Charge Controller *AND* Power PV-Direct Load At Same Time?

I have two 290 watt panels in series that are currently used to charge a 48V battery bank via a MPPT charge controller. The run from the panels to the charge controller and batteries is about 70', and ...
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2answers
55 views

Is my understanding of this level shifter correct?

I am considering using this TI LSF0102 level shifter in my circuit - but would like to understand, based upon its datasheet, if I have my understanding correct. My aim is to be able to supply 3.3V ...
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1answer
63 views

LED Lightbar as a turn signal [closed]

I changed my turn signals to LED light bars the other day. They are completely legal, but the issue I'm having is I can't use my parking lights and turn signals. The bulb that I took out and replaced ...
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1answer
61 views

Buck converter analysis

I have to reverse engineer a PCB of a buck converter and figure out the component values. Given is that Vin = 15-20V and output is ...
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1answer
44 views

BJT-piloted MOSFET circuit: Feedback requested

I had the idea to make a power converter, and I would like some feedback. I can take constructive criticism. The basic idea was to make something where a microcontroller could drive a power MOSFET, ...
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1answer
76 views

How does freezing temperature affect electronic equipment?

What happens if you put a simple circuit like a timer with a 555 IC and, let's say, a DC motor, including 3 AAA batteries in a freezer (around -15 centigrade) in a working state? If it does harm the ...
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1answer
37 views

Why does the TUF formula use \$V_{rms}=\frac{V_m}{\sqrt{2}}\$ and not \$V_{rms}=\frac{V_m}{2}\$ for a half wave rectifier

We know that for a half wave rectifier \$V_{rms}=\frac{V_m}{2}\$ and \$I_{rms}=\frac{I_m}{2}\$ But the Transformer utilization factor uses \$V_{rms}=\frac{V_m}{\sqrt{2}}\$ (But uses \$I_{rms}=\frac{...
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2answers
75 views

230vac / 5vdc power supply design

I am making my own basic bench power supply mainly for testing logic gate circuits, relays, flip flops etc, that I can move around to different locations. The circuit of the entire schematic will be ...
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1answer
33 views

Voltage Circuit Switch with BJT

I have Found One Circuit Which acts as Switch to Pass 15NV (15 Negative Voltage) to Opamps Negative (-VCC) Supply But I am unable to understand its working . Why Two NPN are used in this Circuit ? ...
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0answers
51 views

Discrete DC Connector recommendations - 24v 8.3a [closed]

I need a DC connector for a DIY project I am working on, a high powered LED for an aquarium. I am using a 200 W 24 V power supply in conjuction with 5 Meanwell LDD-H Drivers. I’m hoping to keep all ...
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1answer
59 views

How to choose the right potentiometer for dimming a LED

I have a reading lamp from IKEA. It has a bright LED. Too bright for my taste. So I inspected it and it is composed of a DC power supply unit that outputs 7V and a maximum of 3W. The LED unit is ...
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2answers
58 views

low voltage limits- regulatory

When do I start having to worry about regulatory issues if I sell a product that boosts DC to DC voltages in the 80-100 volt DC range (.5 to 3 amp range) How safe is 48V DC? is the closest i came on ...
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1answer
71 views

Why can't certain isolated DC/DC converters operate at over 50% duty cycle?

I am currently studying two switch isolated DC/DC converters, more specifically the Push-Pull, the Half-Bridge and the Full-Bridge DC/DC converters. Several books say that these converters cannot ...
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1answer
61 views

How can I find the short circuit current across a and b?

In order to find R thevenin, I need to find Isc across a and b since there's a dependent source. Based on my calculations, Vth=500/3V. I've spent countless hours thinking about Isc,please help.
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1answer
36 views

Voltage in a Y-Δ transform

I'm looking for a way to solve the following circuit Without the voltage sources on the circuit, I would be using a simple Y-Δ transform. But I'm not sure how I should proceed with them on. Which ...
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0answers
45 views

Why aren't homopolar generators more commonly used?

In particular with the advent of HVDC(high voltage direct current). Using mercury(metal), the resistive losses can be greatly reduced. There has even been some experimental research into neon plasma ...
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2answers
89 views

DC current gain in complementary transistors

In Class-B amplifiers complementary PNP-NPN transistors are used, e.g. TIP2955 and TIP3055. https://www.electronics-tutorials.ws/transistor/tran_3.html says that They both have a DC current gain, ...
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1answer
40 views

DC Gain too low at higher voltages

I am having an issue with DC gain for a non-inverting op amp circuit. All I am trying to do is double the voltage from two DAC outputs (DAC range is 0 to 5V and I want it to be ~0V to 10V). The DAC ...
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3answers
49 views

AC/DC wattage conversion

I've got some common Dutch "huishoudsnoer" (household-cable? Mainly used for powering lamps. Not solid core, 2*0.75mm² cable) laying around, that's rated for 1380 watts. Our wall sockets provide 230V ...
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3answers
105 views

What enables the home appliances and electronics to work on single-phase?

Talking about the home appliances and electronics, if it is single phase that we are using in houses and currents get to zero every half cycle, how do the home appliances (using AC) and electronics (...
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0answers
32 views

DC Variable power supply

I would like some advice on a particular circuit design for a variable DC power supply. Here is some information about what I want to do: I want to do open and short circuit tests on an alternator ...
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1answer
53 views

Switching Mode Power Supply Fluctuating Output

I designed a switching mode power supply using LNK-562, I share the circuit schematic below. Note that NTC, fuse, and the input filter inductor is replaced with shorts in the real circuits. I am ...
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2answers
52 views

Powering an onboard car GPS tracker

I made a car tracker (a GPS/LTE module connected to an arduino that communicate to my web server) to log gps positionning data. I’m planning to use this to track my new car in case it gets stolen. My ...
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1answer
81 views

A beginner that could use a few tips on wiring my first circuit involving relays

I am in no way experienced or knowledgeable with circuits or electronics passed installing my own car subwoofers and amps, or swapping out pickups on a guitar which means I only basically know how to ...
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0answers
36 views

Pwm DC output smoothing

I'm in the process of assembling a big 25Ah 4S (16.8 v when fully charged) battery pack. The plan is to multi-purpose that to different DC output voltages so the PWM choice felt natural. Now I want ...
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1answer
18 views

Dimming LED with speed controller

I'm trying to controll 4 parallel 12V DC LED strips with an speedcontroller. I am able to dim the lights from 100% lit to about 5% lit, but it never turns them off completely. My multimeter can't ...
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1answer
56 views

Deal with DC offset

I have STM32 BluePill and Teensy 3.2 , they both read analog 0 < x < 3.3V. I want to read earphone microphone sound but the mic produce +-2.5V (with ~200mA, but this is a different problem). ...
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1answer
41 views

Controlling speed of 7 DC motors from Arduino 101 using PWM outside of the audible range

I am researching a way to generate PWM for 7 independent DC motor drivers, each connected to a 12 V DC motor. The drivers take in a PWM signal, a direction signal and a 12 V DC supply and use this to ...
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1answer
45 views

Run a 12 dc power through telephony cable [closed]

I have a converter (120 AC to 12 DC) which is used for sending alert to outdoor through 30 meters telephony cable. My quistion is ( Is it harmful if someone touch the cable? the output can give up to ...
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8answers
3k views

54V 5A DC thru “regular” coax “TV” cable for use as a “poor man's” solar power cable?

In the effort of saving money without having to buy expensive solar cables (and because I have a lot of extra coax cable lying around doing nothing), I would like to use a piece of coax cable (that ...
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1answer
59 views

How to solve this circuit using KCL

I understand the super node aspect of this circuit, but I'm unsure of what to do as I dont see a direct way to proceed with KCL using all of the nodes. I found the equation for the supernode, but I'm ...
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1answer
60 views

Synchronous generator induced EMF

I have started studying synchronous generators in more detail of recent and I'm finding it difficult locating helpful information regarding their operation. What is the formula that can be used to ...
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1answer
31 views

Dusk dawn motor driver with polarity reversal

I'm trying to accomplish this. When a dusk dawn switch is on, drive a small DC motor for a few seconds and then stop. when the dusk dawn switch is turned back off, then turn a small DC motor THE ...
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1answer
48 views

boost converter to high voltages (20kv+)

I am interested in making a mini, potentially portable ion thruster. The Question: Is it possible to create a boost converter that takes low voltage batteries ranging from 3.7V to 24V and boost that ...
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0answers
48 views

Circuit wont work with dc motor

This circuit wont work with the DC motor included but works fine with out it, what can I do to make it work? I need the motor to work when it receives the infrared signal, thanks.
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2answers
65 views

Brake DC MOTOR circuit

I have a DC motor that is controlled with an npn transistor with pwm. Everything works fine. I want to brake the motor instantly. I tried to short the terminals with another pairs of transistors but ...
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1answer
91 views

Power absorbed by load resistor

Can someone double-check where's the mistake? The system didn't accept my answer. TASK: Find the maximum power absorbed by the load resistor, knowing that: $$E = 6.6V; R_{1} = 12.1Ω; R_{2} = 14Ω; R_{...
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1answer
24 views

Using a x-speed transmission with a DC motor

I would like to ask whether there is any point in using a transmission with different gears (like the gearbox in a car) with a DC motor? For instance in an RC car. Are there any benefits to using a ...
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1answer
33 views

Finding indication of ideal ammeter

Would anyone share some tips, advices for solving this task? So far, I have dealt with far simplier electric circuit's tasks. This is new to me. Any kind of help or advices are appreciated, thanks!
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1answer
60 views

Difference between ideal and practical ammeter?

What is the difference between the ideal and practical ammeter? To be more precise, here's my task: I do not need a solution to this. Just looking for a clear explanation between practical and ...
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2answers
164 views

Replaced 4x AA battery with 6V 3A DC adapter, but device won't work

I'm hoping you smart folks can help me. I'm puzzled by what I thought would be a simple DC battery to DC adapter swap. The device I'm trying to mod is a a microchip activated pet door (SureFlap ...