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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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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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47 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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82 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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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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79 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
36 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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1answer
67 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
62 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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75 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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67 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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38 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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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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95 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
41 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
59 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
114 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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36 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
69 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
65 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
87 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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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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60 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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47 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
46 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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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
62 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
80 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
35 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
58 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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2answers
91 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
143 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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26 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
39 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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78 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
175 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 ...
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1answer
76 views

Sound sensor not working when connected to DC motor

I made a small circuit to control a DC motor with a sound sensor, using an ATtiny 85 and an L293D. It worked on breadboard, but now that I have a prototype PCB it ceases to work. Whenever I connect ...
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4answers
116 views

High frequency response of capacitors

I have studied the fact that the capacitor does not like a varying voltage across its terminals, and it acts as a short circuit initially so that there is no voltage drop across it. If this is true, ...
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1answer
57 views

NGSPICE dc simulation error

I want to do dc simulation of differential amplifier circuit, and this is my .cir file looks like: When i run simulation, ngspice give me an erorr: Supplies reduced to 0.1000% Warning: singular ...
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89 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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4answers
140 views

Controlling DC 90V motor with Raspberry Pi or Arduino

I have project where 90v dc rotating motors(4 of them) must be controlled via Laptop. What is the most simple solution, Can I go with raspberry pi or need to go lower with arduino or there are ...
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0answers
43 views

Isolated vs non-isolated boost converter for LED (12v to 24v)

I have a 12v system in my motorhome and planning on installing 24v LED strips, however, I'm unsure whether I would need an isolated or a non-isolated boost converter. I'll be using roughly 5 meters ...
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1answer
67 views

Differential transimpedance amplifier

I have found an opamp schematic that I don't understand. As far as I know a transimpedance amplifier "converts" my input current into an output voltage. But in this case the positive and the negative ...
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2answers
63 views

Is it possible to induce negative/positive charge wirelessly

Sorry if this question doesnt belong here. I have no clue of what I'm about to ask. I want to know, if possible, how to induce negative/positive charge on objects inside recipients? What I want to ...
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2answers
131 views

What will happen if I powered a 24VDC device from a 27.8VDC power supply?

I have a device which has a power input from 12-24VDC Auto select and 250 mA load. I connected it with an online DC UPS which has an output of 27.8 VDC on grid mode and 24 VDC on Battery Mode. I ...
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1answer
36 views

How would I limit speed of dc motor being used as a generator?

How would I limit speed of a DC motor being used as a generator? For a project where I have to make a wind turbine that will automatically limit speed of rotation once past a certain value. Thanks :)
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4answers
72 views

How to find max load limit in datasheet?

I have а datasheet but I don't understand: how to find max load limit in datasheet? Can I use this SSR to switch the load (12V DC), and what current can I count on? Thanks.
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1answer
142 views

Will an AC series motor work with DC supply?

I have read that a DC series motor can be operated using AC supply, but there will be excessive heating in the core and yoke and also a low power factor. So, construction is modified to have laminated ...
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1answer
130 views

What are the symbols in the picture?

Not brilliant pic but bigger picture from UK vehicle wiring diagram, windscreen wiper motor.
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1answer
65 views

How to solve a circuit network involving a resistor parallel to a voltage source using only nodal analysis?

I have been stuck on this for the past week and this week i just dont seem to find out what am i doing wrong. Please help me spot my mistake. Here you can find My circuit on multisim. Please provide ...
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2answers
60 views

Equivalent circuits with one or multiple resistors

I am designing a circuit but I am facing a repetitive design that require too many resistors. The problem comes down to answering if the next two circuits are equivalent in terms of voltage drops: ...