Questions tagged [circuits]

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1 vote
73 views

Transient analysis of first order circuit

For the attached problem, I am getting the signs wrong.Here I have considered the inductor voltage signs as such because after closing the switch, less current would flow through the inductor but ...
• 13
68 views

Cyclic Voltammetry for a Capacitor - Positive Current, Potential is decreasing?

In the boxed red region, why is the potential decreasing when the current is still positive? To my understanding, when the current is still positive (i.e. not changing direction), the capacitor will ...
1 vote
149 views

Same formulas give different answers [closed]

Practice Problem 6.66 from Fundamentals of Electric Circuits, Sadiku and Alexander Q. The current i(t) through a 20 mH inductor is equal, in magnitude, to the voltage across it for all values of time. ...
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1k views

Finding the voltage of a simple circuit

I'm trying to understand the solution of a circuit wrote by my professor. The problem asks to find the voltage across A and B in the following circuit: The solution provided is the following (where || ...
85 views

LM358P not functioning as a non-inverting amplifier

I am trying to make a simple non inverting amplifier using an LM358P. I have run into a problem: the output voltage is 0. I have tried both amplifiers on the chip. I have listed the pin configuration ...
1 vote
132 views

How to determine in a nonlinear circuit with multiple diodes which diode is ON vs which one is OFF? Does it depend on the orientation of circuit?

This problem is from the Sedra Smith Microelectronic Circuits textbook 7th edition. There are solutions available online but I am having trouble how they determined that in part b, D1 is forward ...
187 views

Problem with battery power circuit

I am a 14 years old boy and I am currently making a MacroPad with a 3.7V battery and a charging circuit but powering the circuit with a battery does not seem to work. I also have made some ...
• 355
224 views

Nodal Analysis question that I am finding hard

I seem to be really struggling with this question. I see that there are two current sources in parallel. I combined them and got 2+0.2*Vx. And then, I tried to do voltage division but that obviously ...
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1 vote
64 views

Is it safe to remove this LED from that motherboard? [closed]

So, I've bought this SATA case from internet but it has a really bright light on it and annoys me. I don't haver any kind of tool to manage any electronic component, and neither have electrical tape ...
• 13
129 views

How to find the strongest frequency in a signal using a microcontroller/circuit?

I am trying to implement a low-power backscatter transmitter+receiver and ran into some trouble on the transmission side. Setup: My transmitter circuit sends a 50MHz wave, which the receiver circuit ...
162 views

I can't figure out what this transistor example circuit does. Any ideas? [closed]

I was looking up transistor circuit examples and stumbled upon this one. I can't figure out what this circuit does. Image source - page 5 in this PDF. Sorry, the original document (linked above) is ...
162 views

Falstad Circuit - Why is the current still flowing through the transistors?

I'm trying to simulate a simple signal amplifying circuit using three transistors as shown below: (Note that the LED isn't turned on) But when I open the switch, the current still flows normally from ...
50 views

Inductor sign with single line on the top

I am new to schematics, so can someone help me understand what this part of the circuit means? What does "FB" stand for there, and which components should I use? I guess these are inductors, ...
138 views

From FLA to MCA - NEC

I have a piece of equipment with an FLA (Full Load Amps) of X amperes, and it is a small circuit appliance. Is there a rule in NEC to calculate the MCA (Minimum Circuit Ampacity) based on the FLA. MCA ...
65 views

Voltage drops across a series circuit

How come when I hook up two 10M resistors in series with a input voltage of 12 the two resistors only read 3V each? Should it be closer to 6V each?
1 vote
104 views

60Ω resistor in series with inductor with 80 Ω reactance, connected to 100V. How to calculate the impedance?

I do not have the frequency so I'm stuck. Which formula can I use to get frequency? And can I then, after getting frequency, substitute it into XL= 2πfL to get inductance or should I manipulate this ...
1 vote
458 views

Recently I have been thinking about a circuits problem that caused me a lot of confusion. First of all we know from thermodynamics that energy is conserved. I wanted to show a problem that seemed to ...
• 179
296 views

Sometimes when I use KCL for nodes in a circuit I cannot correctly determine the direction of the currents. My book also says that according to KCL the algebraic sum of currents entering a node is ...
430 views

Capacitor function in a flip flop circuit

I'm new to electronics and I'm trying to figure out the following circuit. The circuit turns on one of the leds when one button is clicked, if the other is clicked then the current light is turned off ...
• 141
774 views

Electrical counterpart: Logical not

I'm building a circuit where I must receive a signal from a logical not. More specifically, I'm looking for a real-life electrical circuit element/component that provides power/signal on the output ...
• 45
75 views

Instrumental amplifier outputs in 12 lead ECG [closed]

Currently we are trying to build 12 lead ECG circuit, so we just need to know the answers to couple of questions. Why do instrumental amplifiers on given circuit have two outputs? How are they ...
155 views

How to write clock process triggering hold and reset pulses in VHDL?

I am attempting to write VHDL for generating control signals to operate a switched integrator circuit. I'd like to create a 20us 50% duty cycle hold signal and a 5us reset signal when the hold signal ...
185 views

Non-planar circuits by mesh method

They ask me to find a way to calculate the voltage between a and b but without using the node method, only the mesh method
318 views

How to connect a 4x4 matrix keypad to one analog pin?

I watched this video on YouTube, the video's creator shows how we can connect a keypad to just one single analog pin of Arduino UNO instead of using (number of columns + number of rows) pins by using ...
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119 views

Can anyone identify this IC on an RGB cross-fading circuit?

Q1 is an IC. I just used that symbol as a placeholder. So all this chip does is gradually brighten and dim each of the LED lines, in overlapping intervals. So red brightens, then as red dims, green ...
1 vote
454 views

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1 vote
83 views

NMOS is high when gate is low

I’m trying to simulate DRAM with N-MOSFETs with row and column selecting logic. When I select my column, which is connected to the source of an N-MOSFET, the N-MOSFETs in that column all turn on, even ...
• 11
92 views

What type of switch would this be? 4PDT or something else?

I’m having trouble reading this switch diagram. The description says the switch contains 6 internal switches but does that mean the that’s a 6PDT? Or is it a 4PDT? Or something else entirely. I ...
180 views

Connecting multiple DC motors together to charge a 12 V battery

I have five small DC motors all rated for 12 V. I am trying to get them all connected together so it will act as multiple wind turbines and charge a battery. However, I am very new to electricity ...
153 views

How can I find values for resistors and capacitors for an active bandpass filter with Rauch structure?

I have to find the values of the resistors and capacitors for this type of bandpass filter in order to obtain 105.5 MHz and 99,9MHz. I have found the transfer function, m, wc and the gain: I am ...
2k views

How to solve combination circuits? [closed]

We were asked to find the total current and voltage, and also the individual currents and voltages of each resistor. Please teach me the steps for solving each of the circuits, and if you have any ...
444 views

Finding the transfer function and damping coefficient an LCR circuit

I am trying to determine the general transfer function of the following circuit. Shouldn’t the transfer function just be $R + \frac{Z_CZ_L}{(Z_C+Z_L)}$? I am trying to then use the transfer ...
1 vote
63 views

How to find values of resistor and capacitors with given formula, circuit and plot

I have given circuit And i need to find values of R1,R2 and C1, C2. Value of E is 20 V and I is 2 A. I just need tips how to start this task.
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286 views

Usage of input voltages in ideal op-amp

Why is the difference between inverting and non-inverting voltages in an ideal op-amp equal to zero in many problems? I can't seem to get that. Let's say that if the difference voltage equals zero, ...
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56 views

Can both forward and feedback gain in an oscillator circuit be unity?

Let us consider the case of the oscillator in the given image. By barkhausen criteria Forward_path_gain(A) * Feedback_path_gain(b) =1. With the phase shift being 0 or 360 degrees. My doubts are: In ...
104 views

Why do we use open loop voltage gain in Miller's theorem? Shouldn't we use the closed loop voltage gain?

Let us take the case of the circuit in the image, while splitting the capacitor connected from base to collector into separate input and output capacitors as shown in the second figure. We use Miller'...
1k views

What is the circuit symbol for a triple gang potentiometer?

What is the circuit symbol for a triple gang potentiometer? I've found one possibility for dual gang potentiometers: (Image source: Components101 - Different Types Of Potentiometers And How To Use ...
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248 views

How to find a missing resistor?

This seems to be a really simple question. I'm not really sure where I went wrong in my solution. Please forgive me if this seems irritatingly simple, I've only just started learning about electric ...
1 vote
246 views

How to simplify this complex DC circuit?

I find it very hard to simplify this circuit. Currently practicing for my removal exam and this was one of the problems I failed on one of my previous exams. Especially the middle part makes me so ...
2k views

Paradox: potentiometer short circuits between tracks which never touch

I can solder and use basic features of multimeter so excuse my ignorance. This is driving me crazy, this a potentiometer from speakers which lost left channel sound. I disconnected the volume control (...
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74 views

PWM controller and analog circuits

I’m trying to fix an item controlled by analog circuitry. No luck on that. I can get a motor to run but can not figure out the speed control circuit. It uses NPN and PNP transistors with variable ...
1 vote
48 views

I want to get a NRF24L01 transceiver to use as a switch to wake up a toy, but is it possible to use it without a separate controller attached?

To give more detail, the toy I'm trying to modify has a reset pin that I would like to tap remotely, as it goes to sleep after a few minutes and hitting that reset pin wakes it up. As such, while I do ...
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331 views

Short circuit behavior in very complex circuits (First Order RL and RC circuit problems)

I do know that a resistor is by passed when parallel to a short circuit or wire with no branches. However what if it was within a complex circuit and not just in the outer loop how does that by-passed ...
3k views

"Circuits" - A convenient teaching tool?

At school, we are taught that electricity requires a complete circuit for current to flow. We are later taught that current flows from areas of high voltage to lower voltage. So, current can always ...
132 views

Will swapping a SCR with an SSR increase max current?

We have a system at my work that controls a furnace via a NI cRIO. This circuit currently uses a SCR (model listed below) with the cRIO to switch power out to the furnace. I don't want to get into the ...
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168 views

How do you build this circuit on a breadboard?

How do you build this circuit on a breadboard?
1 vote
1k views

Finding Voltages using Mesh Analysis

The answers are V1= 3.043 , V2= -6.956 , V3= 0.6522. I've already searched how to use mesh analysis to find voltage, there are a lot with this example but they all used nodal analysis to find V1 , V2 &...
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603 views

Calculate the circuit time constant, the supply current after 2 seconds and the capacitor voltage after 3 seconds?

So far I have answered a and b however I am not sure if and when to convert the units to SI and what unit of measurement we leave our final answer. And if I have made any mistakes on the way please ...
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1 vote
719 views

If the total resistance of the circuit is 5 Ω, determine the value of R3

So far I have answered question 1a and parts of b. This is my step by step process: 1a) P=IV P = V/R x V P = 20/10 x 20 P = 40 W b) RT = 5, R1 = 10, R2 = 5; R3 = ? let R3 = x RT = 5+10+x 5+10+x = 5 ...
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150 views

How to properly wire a power supply to a remote control [duplicate]

I have a remote control for an RC helicopter that I want to hook up to a power supply. Each battery takes 1.5V and I need 6 total. The power supply has a positive and negative terminal. Basically I'm ...
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