Fundamentals of electricity, electronics, components, or theory

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56 views

When to use a 1/4 Watt resistor vs 1/2 Watt resistor

I have never understood the difference between 1/4 & 1/2 watt resistors, and in all of my EE lab courses I have always just used 1/4 Watt resistors. When does one use 1/2 Watt resistors and what ...
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2answers
47 views

Why is current different in 2 identical parallel branches of my circuit?

I'm trying to build the classic thermoregulated fans for an IT cabinet, and I'm struggling with some weird phenomenon. Here is my circuit: simulate this circuit – Schematic created using ...
5
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3answers
421 views

What is the difference between clock and pulse?

What is the difference between clock and pulse ? For example: Is the CLK-signal a pulse ? By the way, why do they invented the term frequence ? In my point of view, they could have said 20 times ...
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1answer
93 views

What is the difference between wavelength and period?

Currently I have some problems with basic terms and need some help please. I'd like to know: What difference exists between wavelength and period ? When should I use the name wavelength and ...
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1answer
38 views

Using Metal thumb tacks to trigger events

I am new and curious to electronics, The below video shows a circuit bent keyboard using a keyboard made of thumb tacks to control the note input. I would love to know how this was done. The video: ...
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5answers
71 views

Does increasing the amplitude of a signal also increase the data rate?

I face an ambiguity when considering the carrier frequency, signal frequency, bandwidth and data rate. When I consider the Shannon formula, I wonder if increasing the transmission power also means ...
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1answer
65 views

Understanding this LPF in opamp feedback loop

I'm using a basic opamp driven mosfet to implement a precision low current sink for an LED: This seems to work just fine within the range that I want it (10mA or so). I've seen other circuits that ...
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1answer
43 views

Basic NFC Loop Design on PCB

I'm a college student learning the basics of NFC loop antenna design. As a starting point, I'm trying to design a PCB-based rectangular NFC loop operating at 13.56 MHz, matched to 50Ω. (NFC ...
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6answers
807 views

To what are transistor's “E, B, C” voltages relative to?

I've seen \$V_{CE}\$ and \$V_{BE}\$ in context of transistors, where they clearly denote a voltage between two points. But then I also see things such as: From a table in Wikipedia: ...
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0answers
41 views

pcb trace current limitations

i did try some calculators but some of them is complicated and i've got lost i've a width of about 2mm and depth of 1-3mm, how much current could they handle ? what if i feed them more current ...
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1answer
36 views

Small UPS for bluetooth audio device

I've got a bluetooth audio receiver in my car and am finding it annoying that it turns off immediately after the ignition is turned off. For example if we're stopped for a while I prefer to turn the ...
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1answer
78 views

Does electric potential influence the direction of current?

Main goal My main goal right now is trying to understand what negative voltage means, since I know AC can have a negative voltage and so can any electric component. I've pretty much read and seen ...
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1answer
27 views

Question about the superposition-theorem

I had this exam question, where I was asked to solve a circuit with the superposition theorem. I did it by mesh analysis because I didn't read correctly, but to check my procedure I did a different ...
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1answer
47 views

Leftover current after current limiting resistor

This question is related to my another question here. In crux, I would like to sink current of TLP521 via 74HC595n shift register. The TLP521 is connected with a resistance such that the current is ...
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5answers
663 views

Why pulsed DC passes through a capacitor?

OK, the current flowing through a capacitor equals C*dV/dt, I'm aware of that. What I don't understand is the physics of the process: why does a capacitor pass pulsed DC (0-10V for example) when ...
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1answer
31 views

would this be safe to control servo with usb

i've been asking around and people has been telling me that the max current a usb can supply is 100 ma then 200 ma then 500ma then the http://en.wikipedia.org/wiki/USB says 0.5–0.9 A (general) 5 A ...
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1answer
57 views

Calculating the gauge of wire required for the secondary in a Tesla Coil

I am looking to build a small Tesla Coil at home with limited supplies. I am reasonably confident (well.. as confident as a biologist can be!) with my calculations so far, however I have hit a mental ...
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0answers
62 views

voltage and current amplifier

voltage amplifier does voltage amplification current amplifier does current amplification Is there something like power amplifier or power amplifier is just same as current amplifier?
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3answers
83 views

Help Trobleshooting my first solderless circuit on a breadboard

I'm working on my first project from the book "Electronics All in One for dummies", chapter 6, book 1. I work through all the instruction but I cannot make the LED blinks. The circuit diagram is: ...
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1answer
169 views

Learning the Basics of Circuit Design [closed]

This question was put on hold, citing the fact that any answer would be based on opinion. I can't really argue that point, but I do believe that in this case the point is irrelevant. I am asking for ...
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1answer
63 views

What is the equivalent of a beep on a multimeter without a beeping function?

I have a multimeter that does not have a beeping fucntion and I need to test for continuity. Set to 200 Ω, the multimeter shows 1 when the probes aren't touching, ...
3
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2answers
185 views

RLC - Understanding Phase Shifts

I'm having trouble understanding intuitively phase shift for RLC circuits. For example, I have seen the following: In the low-frequency regime, which element is the dominating element (highest ...
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1answer
70 views

Bypassing input capacitor with a microcontroller

I am designing an amplifier stage and I would like to be able to switch between AC or DC input coupling. How do I achieve this with a microcontroller? I was thinking about using a relay, but it ...
4
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3answers
608 views

Calculate op-amp output voltage

I am trying to calculate the output voltage of the circuit. I know that this is a voltage follower, but I am trying to understand how it works. simulate this circuit – Schematic created ...
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2answers
283 views

Why 10Log(p1/p2) and 20Log(v1/v2)? Why not just 10Log(x1/x2)? [duplicate]

Based on my very basic current understanding of decibels in electronics, it is said that I should use the db = 10Log(p1/p2) formula if I want to calculate the power ...
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1answer
152 views

Insufficient ground supply on my circuit? Ground capacitive foil

I'm playing with a wireless sensor device (with atmega, xbee, and Capacitive sensor (simple foil)) that works fine with the lab power supply but as soon as I try it with AA batteries stops working. ...
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8answers
884 views

When does the placement of a resistor matter?

I've been a programmer for years but am very new to electronic engineering. So far I see people saying it doesn't matter where a resistor goes in your LED circuit as long as it is present, but it ...
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2answers
129 views

Only Allow One LED To Light Up

I'm trying to design a simple circuit for a 4 LED indicator. Its basically like a game show device that has four buttons. The first one to press their button would have their LED light up and "lock" ...
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1answer
143 views

Basic voltage divider issue in my amateur circuit XBee

Once again I need your help in my project. I have a 4,5v powered circuit. I put a voltage divider with 2 resistors in series to reduce my initial voltage of 4.5V to 3.4V (to feed an XBee module). The ...
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3answers
203 views

Why use a resistor for Pull-Up? [duplicate]

I just got my first Arduino and had a question about pull-up resistors. I was trying to connect a push-button to the Arduino at pin 2, and if it's HIGH then I write HIGH to pin 13. Now, in the ...
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1answer
167 views

How can I create an SCR using a PNP and NPN?

Several times I have seen an SCR described as similar to a PNP and NPN transistor linked together. But any attempt to replicate the idea seems to fail. In the circuit below, for example, the LED is ...
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2answers
124 views

What Does Rated Load of a Tactile Switch Mean?

I want to connect a tactile switch to an GPIO pin of MSP430 (which runs on 3.3 volts). The datasheet of the micro-controller says that IO pins can withstand max current of 6mA. The tactile switch I ...
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1answer
328 views

Arduino + transistor to switch PC fan on/off

I have: an Arduino UNO a 12V PC fan with 1.68W rating (140ma). 2n3904 transistor 12V 500ma power supply to connect to Vin. What I would like to do is to simply use a digital output pin on the ...
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2answers
122 views

LEDs, Voltage and Resistors

I noticed that a Christmas Light uses 20 LEDs in series parallel, operated by 2 AA batteries (3V) without a resistor. I thought you always need a resistor? Would it be possible to run them on 5V ...
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1answer
98 views

Photo transistor in parallel

I'm a beginner and trying to figure out how this circuit works (its a simple circuit that glows an LED when dark) : https://www.youtube.com/watch?v=eIGWWKThprI&list=UUhtY6O8Ahw2cz05PS2GhUbg#t=65 ...
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1answer
64 views

Electronics by Example [closed]

I am interested in learning more about electronics. I know some basics about resistors, capacitors, transistors, and diodes. I would like to learn more about things such as operational amplifiers, ...
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2answers
113 views

How do I solder to these pads?

Quick question. I'm trying solder some wires onto the 5 pads (top right of board) in the image. What's the best way to achieve this? I cant get the solder to stick to the board and I have no flux. I ...
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4answers
1k 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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4answers
174 views

How and why is a magnetic field transmitted with alternating current?

I apologize for the basic question (or if it is incorrect in its assumptions,) but how does one account for magnetism in alternating current? If I generate alternating current to a motor, why do my ...
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1answer
483 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
291 views

Mounting AC-DC converter on PCB

I need to figure out how to physically mount the following AC-DC converter to a PCB to be used as part of a regulated power supply. The pin height is min 3.0 mm. Should I mount it as a through-hole ...
0
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1answer
60 views

Should I assign currents to voltage sources in my circuit analysis

Mortals! I apologize if my question may seem, foolish, but I have a need of understanding a process in analyzing circuits. You see, when we are looking at resistors (non-sense, my lightning never ...
18
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9answers
2k views

Why are electrons not pushed out from the conductor at an open circuit under the influence of a power source?

Frequently, electric current is compared with water flow. For example, if I make a hole in a water tank, water will flow till the tank pressure and the atmospheric not become equal or the tank becomes ...
0
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6answers
187 views

Closing two circuits from one button press, with a delay?

From one button press, I want to momentarily close two circuits with a small (< 1s) tuneable delay in between. What term should I google for to find a schematic? (For clarity, I want to press the ...
0
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3answers
180 views

Working of RC Phase shift Oscillator?

Figure show a RC phase shift oscillator using Op-Amp with gain 5(Vo/Vi). My assumption : Circuit is generating a sine wave with a peak to peak voltage of 10v. Consider positive maximum point (+5V) ...
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1answer
77 views

Components Purposes. Just need a verification

I just need to know if there is anything I need to add or remove. And also What is the purpose of a switch transistor(Q1)? I need a simplified explanation. Thanks in advance
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2answers
177 views

Why does AC Current exists? [closed]

I need to know why does AC Current exists? And why not only DC current exists? Most devices needs DC current. I know that DC current is much dangerous then AC current. because of it is alternating ...
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3answers
1k views

What operation could cause the inductor or the capacitor to explode?

In really early days of electronic school, the teacher used to say something about not unplug power too quickly at an inductor or capacitor and we were used to slowly turn the voltage generator from a ...
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2answers
224 views

What are quartz crystal oscillators?

I'm a beginner in electronics and I found two quartz crystal oscillators, each one has two pins. Their numbers are: sjc4.000a ee4.000 Is it possible to know the ...
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2answers
176 views

How can two steel balls with same amount of charge be at different voltages?

Maybe this is the most fundamental question, but still it eludes me. Is it possible for two balls each containing 1 Coulomb of charge be at different voltage levels, say 1V and 2V relative to a ...