A resistor obeys Ohm's law (V=IR); the current through it is equal to the voltage across it divided by the resistance (equivalently \$I=\frac{V}{R}\$)

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2answers
78 views

Calculate mosfet gate resistor?

I got this schematic : In the image you see; I'm driving two infrared leds at 40 Ma each one with a FDN327N Mosfet. Attached at D8 there is one of Teensy 3.1 digital output that has HIGH voltage ...
8
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4answers
924 views

555 timer: how to set values to take an hour

I'm new (and novice) in electronics. I came to seek your knowledge to see if someone can help me with a very basic circuit. It is a 555 chip, which should light a LED (for about 1/2 second) every ...
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1answer
57 views

Calculation of base current resistor resistance for a transistor operating in switch mode? [duplicate]

I have a 9V DC motor and I want to control its speed with an Arduino board with help of a power transistor TIP120. In one of the web-tutorials the writer explains how to calculate the resistor ...
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1answer
87 views

9v battery to parallel 3v LEDs - burnout

I'm having an issue in a simple (n00b) LED circuite - ended up burning out a couple of LEDs due to some mistake I'm making, but can't figure out what the error is. I've got a 9v battery, trying to ...
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1answer
34 views

MAx peak to peak of ES without clipping?

This is an exam problem in which my instructor gave the answers but no work. Any one has an idea of how to solve it;FOM(figure of merit)= 25/125, RL=15 ohms, Rx=250 ohms, r1,r2,vee,vcc, are not given. ...
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4answers
457 views

Turn a transistor on when any one of nine LEDs is on using an LM3914

I'm wanting to turn a transistor on when any LED from LED2 through LED10 are on with an LM3914 in dot mode. Basically, I want the transistor to be normally off until at least LED2 begins to light ...
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1answer
66 views

Make three respective LEDs blink with an LM3914 in dot mode

I'm trying to figure out how to make in the below schematic, LEDs D2, D3, and D4 blink respectively while the LM3914 is in dot mode when their on state occurs. Basically this would act like a warning ...
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3answers
93 views

Resistors in series or one after?

I want to use a Voltage divider and i need to divide 5v to ~3.3 so I ordered 10K resistors on eBay, but the voltage divider needs a 20K and a 10K, can i use 2 10K's parralel as a 20K
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1answer
34 views

Power resistors equivalent thermal model: Interpretation of datasheet & 0°C terminal of power source

This is borderline electronics, but I think many more of us here have done this kind of studies. I'm heating an aluminium plate with an Aluminium clad power resistor by mounting it on it and applying ...
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1answer
65 views

What are the failure modes of resistors, inductors, capacitors, diodes, transistors in conditions of overvoltage or overcurrent? [on hold]

What are the failure modes of resistors, inductors, capacitors, diodes, transistors in conditions of overvoltage or overcurrent? Example: ...
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1answer
64 views

Resistance calculation for transistor base

I read this question's answer on calculating the base resistor value for a 2N3904 transistor. I'm in a similar situation however I'm using a TIP3055 to switch a \$V_{CE}\$ of 12V and a \$I_{CE}\$ of ...
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1answer
50 views

Multiple shunt resistor INA226

For a project I'm trying to build a measurement tool for USB where I can measure U, I and P using the INA226 from Texas Instruments. The shunt resistors all have a different value to measure a ...
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6answers
416 views

Need to build a circuit resembling fluid flow through porous media

I am trying to use electronics analogy to build a model that describes fluid flow in a porous media. For example I consider voltage, current and resistance to be equivalents of pressure, flow rate and ...
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2answers
52 views

A simple RL circuit, getting transfer function, matching with results

I'm doing little lab exercise with an RL circuit. I need to check if I did this analysis right, because the numbers I got and the numbers that should theoretically be there are so far off, I figured ...
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1answer
83 views

What happens when the voltage drop does not equal voltage rise in a closed series circuit?

New to electronics. Can't get my head around so many basic things but the application of KVL is bugging me the most. I want to know what happens when Kirchoff's voltage law is broken. If for example, ...
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2answers
61 views

Problem with a circuit of an controlled variable voltage source

I have this circuit, it should regulate the output voltage between 15V and 0V. But the output I get when I simulate it is between 2V and 3V, and when I implemented, I burned zener diode 1N4734A. ...
2
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1answer
71 views

Can I extrapolate the rated overload spec of a wirewound resistor to a joule rating?

I'm considering using a Vishay FVT series resistor for precharging some capacitors. Capacitance: 3300uF Voltage: 730V Resistance: 500 ohms Resistor continuous wattage: 25W This series, like many ...
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2answers
138 views

Can I use DC resistor in 220 V AC circuit?

Can I use DC resistors as AC resistor? If yes, is there any problem interfacing with it? Please recommend AC resistors for working with 220 V AC 50 Hz.
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1answer
36 views

How to wire multiple 2 volt flickering LEDs to work on 12V auto system

I have tried to use the site to find an answer to this, but it seems everyone that has asked questions have different variables than I am dealing with, and I can't ever seem to grasp electrical ...
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2answers
269 views

How to measure current practically in a circuit

I have to measure this circuit, I have done the theoretical calculations using Kirchhoff's 2nd law, but I'm having troubles in measuring the current in each part of the circuit: I have to measure ...
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1answer
82 views

Toggle transistors with an shiftregister to light up an LED

First of all I'm quit new to electrical engineering. I had it 3 years in class but I didn't do well. So here is what I plan. I got some shift-registers (74HC595) Which I'll set with an arduino mega ...
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0answers
144 views

Integrated LED + Resistor + Transistor

Most designers when are controlling an LED have to make the same old circuit of Vcc -> Resistor -> LED -> Transistor (you need the transistor in case your ...
2
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3answers
173 views

Rule of thumb for LED Ballast Resistor

As well all know, using an LED without some sort of current control is a bad idea. One of the most basic types is a simple Ballast Resistor, paired with Ohm's Law. Based on Vin, Vf, and the desired ...
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1answer
50 views

Drain Li-Ion battery by connecting USB +5V and GND

I have a sportswatch which can be connected to a PC via USB for downloading the training information, upgrading the firmware, etc. I have used those features for a year on weekly basis, but since ...
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1answer
45 views

Why is voltage properly siphoned off in this circuit?

This comes from the Raspberry Pi "fart detector" project. It says to place a 47k Ohm resistor connected to ground in order to siphon off a certain amount of voltage so that the voltage read from the ...
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1answer
48 views

Heat dissipation

I have a computer power supply and I'm wanting to make it a variable voltage power supply but I have to have a load on it which requires some resistance. I have connected a 10 ohm 10 watt at 10% ...
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1answer
95 views

LED's too dim. Wrong resistor?

I'm a halloween tinkerer, and I have these UV/Blacklight flashlights that I use in my decor, but they eat batteries like crazy. They start going dim within an hour or so. So, since I already have ...
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0answers
136 views

Calculating the resistor's power consumption of 1 ohm in watts

I ran into a old-midterm exam question that calculate the one-ohm resistor's power consumption in the following diagram in watts? I need some solution or hints. I try to solve it but I think the ...
0
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1answer
97 views

What's the thermal time constant/capacitance of a 1/4W resistor?

I can't find it anywhere, what is the thermal time constant or thermal capacitance of a standard discrete 1/2W resistor? A table with other resistors of different power ratings would be nice, too.
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2answers
46 views

Why does a headphone attenuator need separate resistance for each side instead of a shared resistor for both?

I have a Shure headphone attenuator and opening it up it looks like there are separate pins on the pot for the left and right speakers (the pot has 5 pins, which I believe are left in/out, right ...
3
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4answers
619 views

DC Motor + 9 V battery + 270 ohm resistor = Nothing (Motor won't turn)

I'm trying to wire up a DC motor to a 9-volt battery with a resistor in between, and the motor just won't turn. It works if I connect the motor directly to the battery, but not with the resistor in ...
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1answer
67 views

Touch dimmer with low voltage transformers, needs incandescent to work? Updated!

I've looked extensively about this topic, and can't find any answers. Hopefully someone on here can help. I live in Texas and have 120V power in my house. I'm using a lamp touch dimmer to dim two ...
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1answer
98 views

What does lumped element mean?

Can anyone explain me the meaning of lumped element and lumped circuit abstraction in detail. What does lumping or discretizing matter mean?
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1answer
70 views

Calculating total resistance for this circuit?

I'm very lost in my ECE class right now and I was hoping someone could help me out and explain what they're doing. I was asked to calculate the total resistance. After getting that, I was asked to ...
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1answer
63 views

AC source in parallel with resistor problem [closed]

For an AC source of for example +-12 V, can a connected resistor at any instant, have 24 V across it? Because my textbook has a problem in it involving such a source and says (hint: consider the ...
0
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2answers
76 views

Calculating the Resistor's Power Rating

I'm designing a couple of step-down voltage regulators based on a LM22677 chip (datasheet) and following the example: I want to get 5V and 10V from a 12V supply, but I have concerns regarding the ...
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0answers
50 views

Resistor and LED Bias

My question pertains to this sketch of a project called the Quiz-O-Tron 3000. I wired up the proto-sheild and the 4 button switches. When I went back through my inspection and testing of the units, ...
0
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1answer
66 views

Adjustable charge current from programming resistor for Li-Ion charger - how to change on demand?

I am designing a device which has an integrated Li-Ion battery (single cell, for simple low power portable digital device) and normally charges by way of a buck converter which goes from 12-16V ...
2
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3answers
515 views

How do I find the resistance between three terminals?

I'm trying to self-study this problem and I found a bizarre problem with an unusual circuit. I have never faced this in all the problems that I have solved. What do they mean by finding the ...
2
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1answer
39 views

Trimmer pot to fixed resistor conversion

Sorry for the simplicity of this question but I've been struggling on this circuit for a while. In the schematic link below you'll see a trimmer pot and I simply want to replace it with one/two fixed ...
1
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2answers
131 views

Op-amp differentiator and integrator circuit: resistor and capacitor values

I don't understand how to determine value of resistors and capacitor in differentiator and integrator circuit of Op-Amp. I tried to align the amplitudes of these sine waves. I keep changing their ...
1
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4answers
118 views

Ohm's law clarification

I am slightly confused about Ohm's law. I understand V = IR, and I did a simple experiment on paper. The results are slightly confusing, so I was hoping someone could tell me if I'm right? First, I ...
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1answer
71 views

What's wrong with my answer finding the resistance?

This is the question and the solution: Here's my answer: My answer was incorrect, though I believe my analysis was correct. Can anyone point my mistake? I hope it's not with the signs.
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1answer
107 views

The resistor's power consumption of 1 ohm in watts

I ran into a old-midterm exam question that calculate the one-ohm resistor's power consumption in the following diagram in watts? I need some solution or hints. I try to solve it but I think the ...
0
votes
1answer
42 views

Calculating resistor wire properties for my projects

I have a few things I wanna do with the resistor wire. They all involve getting approximate temperature using known voltage. I understand that temperature heavily depends on environment, but what I ...
0
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3answers
67 views

Figuring resistor wattage and value

I have a remote controlled airplane that I am putting LED lights on. The power supply is a lithium polymer battery that is rated at 22.2 volts and 4000 miliamps. I have an LED that is rated between ...
0
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1answer
112 views

Connecting a parallel port to an Arduino

This is my first Arduino project and while I remember a (tiny) bit of electronics from school I'm struggling to get this working - in fact I've just fried a parallel port PCI card! I'm looking to ...
1
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3answers
129 views

Simple Ohm's Law Question

Do I need a resistor if \$\frac{V}{I}=0\$? I am working on a simple circuit of an LED and a buzzer in series where the voltage drop would be 2 and 3 volts, so \$R=\frac{V}{I}=\frac{(5 - (3 + ...
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0answers
46 views

Trouble finding R in a super mesh

I am trying to find \$R\$ in \$R_5\$ via mesh analysis. I see that loops 1 and 2 are a super mesh, so then applying KVL to them I end up with: $$ 4\cdot(i_1-i_2) + R\cdot(i_2-i_3) + 2\cdot i_1 + ...
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1answer
70 views

Is my circuit analysis correct in this problem?

This is the problem: My solution: I'm new the delta-to-y and y-to-delta transformation, it is obvious we need to use them. I got the same answer but I'm a bit skeptical about my solution. Is my ...