Fundamentals of electricity, electronics, components, or theory

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2answers
57 views

Can capacitor charge to higher voltage than source provides?

Hi I played with some basic circuits in lushprojects.com simulator and came up with this one that surprised me - when the capacitor C1 is charged for the first time by pressing the SW1 switch the ...
1
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1answer
159 views

AVR switch best practice

After reading a lot of posts (here and on the web), I am a bit confused. All I want to do is to get the best practice of push button connection to AVR. I have 2 "sections" to my question. the first ...
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1answer
102 views

Basic transistor switch

I'm just an amatuer working with some electronics at home. I am trying to use an NPN transistor as a switch. 9v on the Emitter, 6v as the control on the Base to activate the switch, and I'm going to ...
1
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0answers
44 views

Solving the equation for Common Drain

So I've designed an all NMOS amplifier to further voltage amplify the 5V max output of an Opamp to 24V rails. I used a Common Source at the very end so I'll have a very low output Impedance. Of ...
0
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2answers
65 views

How to properly use ESD protection wristbands

I've looked at other articles on EE stack exchange about ESD precautions. I would like to use a wristband for precaution with microcontrollers. Where am I grounding my wristband to? Do I ground ...
4
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6answers
2k views

How can voltage burn out an LED?

I understand how a current higher than what the LED is rated for can burn out an LED, but how does something equivalent happen with voltage? If the correct current is on an LED but the voltage is too ...
3
votes
1answer
52 views

How can you build a floating two-port VCVS?

I have a control voltage at one point in a circuit which I need to duplicate at various other points (3 or 4, if I remember correctly). I'd like to use one potentiometer to control these voltages, so ...
0
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2answers
51 views

DC Motor: Difference between E and k?

I'm studying for an exam, and have come across a question I don't. really understand The question gives us a back-emf constant and asks for a rated back-emf. Now I know that the back-emf constant is ...
0
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0answers
36 views

Calculate lower-bound for the total average power

I'm studying for an exam and have come across a question question about power lower-bound. In my lectures we have gone through AC peak voltages, \$\sqrt{2}\cdot V_{RMS}\$, I'm not sure if it's related ...
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2answers
128 views

How a transistor works?

I know this question is asked a lot and answered well in many posts, however, I'm still confused. A switch transistor works by using a semiconductor to pass the current from an emitter to a ...
1
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1answer
72 views

calculate Amp Hours when voltage is given

I'm trying to wrap my head around how exactly Amp Hours work. I have been trying to figure out this question for a while now, but can't seem to find the information that I need. This is the ...
2
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2answers
344 views

Where exactly does the ground line go in an AC-DC power supply?

I'm working in the United States. I'm looking into working with mains power, and I cannot for the life of me figure out where the ground line connects. For example, a simple power regulator from mains ...
0
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1answer
53 views

Why does oscilloscope show large amplitude when I touch the probe?

When I touch the probe I see a 50Hz sine wave with an amplitude of about 100V from peak to peak. I understand that 50Hz is the mains hum picked up through my body, which acts as an antenna, but where ...
0
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3answers
78 views

If we put a led light into a oscillating current, will it blink?

Sorry for the misleading title cause I have no electronic knowledge. It is a simple question. This is the circuit diagram. In case you don't see clearly, it is XOR GATE. My question is what will ...
0
votes
4answers
87 views

How to get started with microcontrollers? [closed]

My point is not to start a flame war, or have an opinion based fight. I really just need advice based off of my experience. I am pretty experienced with using an arduino, I understand C, & C++ ...
1
vote
2answers
208 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 ...
0
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2answers
56 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
votes
3answers
494 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 ...
0
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1answer
98 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 ...
0
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1answer
40 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
105 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 ...
1
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1answer
84 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 ...
0
votes
1answer
86 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 ...
3
votes
6answers
839 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: ...
0
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1answer
37 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 ...
0
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1answer
93 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
31 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 ...
0
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1answer
50 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 ...
6
votes
5answers
715 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 ...
0
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1answer
32 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 ...
0
votes
1answer
77 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 ...
0
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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?
3
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3answers
87 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
191 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 ...
1
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1answer
125 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
votes
2answers
214 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 ...
1
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1answer
75 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
votes
3answers
970 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 ...
2
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2answers
557 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 ...
0
votes
2answers
230 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. ...
4
votes
8answers
980 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 ...
2
votes
2answers
158 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" ...
0
votes
1answer
179 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 ...
0
votes
3answers
218 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 ...
0
votes
1answer
237 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 ...
2
votes
2answers
141 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 ...
0
votes
1answer
426 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 ...
0
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2answers
125 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 ...
0
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1answer
111 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
90 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, ...