Fundamentals of electricity, electronics, components, or theory

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8
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4answers
908 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 ...
1
vote
3answers
69 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 ...
1
vote
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?
5
votes
1answer
260 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
votes
1answer
46 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 ...
17
votes
9answers
3k 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
votes
6answers
106 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
votes
3answers
46 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) ...
-1
votes
1answer
75 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
-3
votes
2answers
112 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 ...
16
votes
3answers
2k 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 ...
1
vote
0answers
56 views

How to get the value of a burned resistor on a PCB of Weanas® Plug Power Meter? [closed]

In my house electricity was shut down and came up again a several times during 5 seconds. After that my device - Power meter did not work. It was possible to turn on the device, but it was showing ...
1
vote
2answers
90 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 ...
0
votes
2answers
149 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 ...
1
vote
1answer
70 views

Electrical Engineering Math, showing time independence? how?

I have a cheat sheet provided by the teacher about the calculation of the Coherence Time, however I get lost along the way. There are 2 paths of a signal at: Path 1: \$\phi_1(t) = ...
2
votes
3answers
90 views

What is Doppler Spread

What is the plain English explanation of the Doppler Spread? Looking at different sources I come across complicated definitions which I struggle to understand. Example for such one: Doppler ...
2
votes
2answers
62 views

What makes DSSS a more robust transmission technique compared to FHSS?

In many textbooks it is stated that DSSS is more robust than FHSS. Especially in terms of interference and delay spread? What is the exact reason. Lets say we multiply a given bit 1 with a larger bit ...
0
votes
1answer
60 views

Plain English explanation of the Space-time Code Block by Alamouti

I checked about the Space-time code block online, but all of the explanations are either short or too simple, or too mathematical and complex Could anyone here provide an explanation of what ...
0
votes
2answers
43 views

How are the Intersymbol Interference and Symbol Time (duration) related to each other?

In a lecture slide I noticed that OFDM(Orthogonal frequency-division multiplexing) mitigates the problem of Intersymbol Intereference over wireless systems because the symbol time is increased, in ...
0
votes
1answer
35 views

Generating a desired pulse train in Xilinx ISE software

Need some help with VHDL and FPGA since I am new to it. I have a Virtex-4 FPGA and I wish to generate a binary pulse train of 16 pulses from FPGA using VHDL programming. My desired pulse train will ...
2
votes
2answers
70 views

What phenomena does “Coherence Bandwidth”?

Could anyone please provide a simple explanation of what Coherence Bandwidth means, and how is that related to Delay Spread. I read some articles but they don't help me to form the relation between ...
1
vote
2answers
90 views

Explain Rayleigh Fading in plain English

For a couple of days I am trying to understand the Rayleigh Fading model, but I am failing to. I look at various articles and tutorials online, everything goes fine up to a points, but then a lot of ...
1
vote
2answers
258 views

Connecting a potentiometer

I know how to connect potentiometer, but to be honest I don't know why. I would really like to understand what I'm doing. From what I have read the input voltage and the ground should be connected ...
0
votes
0answers
55 views

Inducing Eddy current in wet clothes

Is it possible to induce eddy current in wet clothes and dry them using the resistance heat generated? I don't want to connect any wires to the clothes.
-2
votes
3answers
199 views

When should you use a transformer instead of a resistor? [closed]

I feel like this was something that was never taught by my instructor in physics. Is there a certain rule determine when a resistor should be used over a transformer, when stepping down voltage?
1
vote
1answer
108 views

Why would we need to ground an AC source?

I'm new to this field hence this weird question. Why would we need to ground an AC source? Why wouldn't it be enough to have just one pole to get an AC current going? I understand why it wouldn't work ...
0
votes
2answers
128 views

How to understand the “basics” of electricity? [closed]

I want to be a self-taught computer engineer ... massive goal, but it's what I want eventually. I check out textbooks and online resources, but I feel like I need a prerequisite somewhat -- I still ...
1
vote
3answers
132 views

Powering multiple relays

I'm trying to control five * 5v relays from a micro-controller. However I'm having issues powering more than two at a time Some notes The power source is a 800ma 10V ac adapter. 7805cv voltage ...
3
votes
1answer
55 views

Capacitor charging: do electrons migrate from the source to the dielectric?

Encyclopedia of Electronic Components - Vol1, pg:98 by Charles Platt Electrons from the power source will migrate on­ to the plate attached to the negative side of the source, and will tend to ...
2
votes
2answers
262 views

Why there isn't current in R3?

simulate this circuit – Schematic created using CircuitLab Why there isn't current in R3? Does it depends on the resistance of R3?
1
vote
1answer
104 views

How R equivalent can be found?

simulate this circuit – Schematic created using CircuitLab How R equivalent can be found (without using star delta connection)? the answer said 3/5R
2
votes
3answers
372 views

How can the SI unit of resistivity [Ωm] be interpreted?

The way I interpret the resistance \$R\$ of a resistor, which has dimensions \$ [\frac{\mathrm{V}}{\mathrm{A}}] \$ is: how many volts must be applied across the resistor to achieve 1 ampere of ...
1
vote
1answer
115 views

Do I need trivial resistor or not if V/I = zero or almost zero

As the title says, do I need trivial resistor or not if V/I = zero or almost zero? For instance: Assume I'm using 3V buzzer and 2V LED in series with an Arduino 5V pin. $$R = \frac{(3 + 2 - ...
0
votes
1answer
119 views

Replacing BJTs with power MOSFET

I have 2 x 2N2222 BJTs powering 2 relays of 200mA each. I am using 2 output pins with 500ohm resistors to power the transistors. After powering it the circuit not working well, while replacing the ...
2
votes
1answer
222 views

BJT base resistor

I read this post: Which resistor for NPN transistor base? But I still cannot understand the base resistor calculation. I need the transistor to be a switch to 5V 200mA relay. The base will get its ...
-2
votes
2answers
142 views

Learning electronic circuit design [closed]

Is there a good website or book to learn electronic circuit design from the beginning. I would like to learn more about basic electronic elements and how to use transistors appropriately in my circuit ...
31
votes
10answers
3k views

What is a Charge?

I'm a high school student. I love computers and electronics. Few weeks ago, I thought to build my own electronic gadget but, unfortunately I had not much knowledge in electronics. So, I decided to ...
0
votes
1answer
69 views

How do I wire up this relay?

I'm making this circuit: I've bought an Omron G5LA-1 non-latching SPDT relay. It looks like this (from the datasheet): I'm struggling to figure out how I wire this up though. I believe I need to ...
9
votes
3answers
1k views

Basic operation of a bipolar junction transistor

I've tried really hard to understand the basic operational principle of a transistor. I've referred to many books and been to forums but have never got a convincing answer. Here are the things I want ...
3
votes
4answers
380 views

Does free electrons from the conductor itself flow or electrons inside the battery flow?

Hello I am new to electronics. I read electricity works this way - some atoms have more electrons than protons. These free electrons flow through a conductor such as a copper wire. However, to induce ...
0
votes
3answers
116 views

Basic question about voltage

The voltage on capacitor is given by $$V_c=\dfrac{1}{C} \int i(t)dt$$ and the current is $$i(t)=0.4 \sin(2t-\frac{\pi}{4})u(t)$$ when u(t) is unit step function. May you show how to integrate the ...
0
votes
1answer
72 views

SSR function con control panel

I'm new in electronics and would like to build an electric brewery with an electronic control panel. I found on www.instructables.com one control panel and is described as in following image. Could ...
2
votes
1answer
173 views

How does a first-timer set up a correctly-grounded workbench / work-station?

I'm new here, and new to electronics in general. (for the most part … my [awesome] father had me building some simple robot-kits with him when I was a kiddo, but I'm getting into it “4srs” for the ...
2
votes
2answers
155 views

How does a NOT gate bypass the output?

I have found the basic tutorials on gates and the way they work. However, I'm not understanding conceptually how a NOT gate, when activated, bypasses the output. Circuit as follows: simulate ...
0
votes
2answers
73 views

Simple Capacitor Wattage Ratings

I am constructing a simple circuit to convert AC power from the wall to a 10V DC power across a load. I am fairly new at this though, so I have a question about how much power a capacitor can handle. ...
0
votes
1answer
141 views

How to connect 3-digit display and suppress leading zeroes?

I searched a little and it told me to use with more than one display, connect (Ripple Blanking Output) from most significant 7447 to the of the next 7447. Which number would be most significant? ...
1
vote
2answers
196 views

L7809CV increasing voltage from 3V to 9V

I just got a voltage regulator and I was playing with it in a simple DC circuit. My Source is 3.25V, the OUT pin on the voltage regulator (L7809CV) shows 2.25. My confusion starts with the 1V drop in ...
15
votes
6answers
4k views

LED and lamp in series - why does the bulb not light?

My 6 year old son has just started experimenting with a Snap Circuits style kit and already we have a very basic question. If we arrange an LED and lamp in parallel powered by batteries then both LED ...
1
vote
2answers
113 views

How can I maintain a fix voltage until my battery is almost dead?

I am experimenting with a simple circuit. I have an Arduino board, a proto-board and an IR sensor (that uses electricity from the Arduino board). I use a 9V battery to feed the Arduino. My problem ...
1
vote
1answer
172 views

Rising Pitch Siren Electronics Circuit Explanation

Can somebody explain me how in detail what is going in this circuit? I tried it and it was working but I cannot understand how this works. ...