Fundamentals of electricity, electronics, components, or theory

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Deriving the Coherence Time? (some of therms get lost)

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
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3answers
33 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
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2answers
49 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 ...
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1answer
57 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 ...
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2answers
36 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 ...
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1answer
29 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 ...
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2answers
60 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 ...
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2answers
72 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 ...
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2answers
188 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 ...
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0answers
52 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.
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3answers
138 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?
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1answer
81 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 ...
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2answers
106 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 ...
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3answers
97 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
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1answer
48 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
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2answers
257 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?
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1answer
100 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
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3answers
303 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 ...
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1answer
113 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 - ...
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1answer
98 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
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1answer
138 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 ...
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2answers
97 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 ...
32
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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
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1answer
64 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
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3answers
754 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
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4answers
312 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
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3answers
113 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 ...
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1answer
54 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
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1answer
122 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
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2answers
147 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 ...
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2answers
68 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
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1answer
124 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? ...
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2answers
159 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 ...
14
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6answers
3k 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 ...
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2answers
99 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 ...
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1answer
134 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. ...
0
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1answer
165 views

Create a simple flip flop circuit

I am just taking a electronics course, and i am trying to understand how to build a flip flop circuit. I would like to build a circuit that has one push button, and one led. Each time the push ...
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2answers
83 views

What do I do with the “shell stakes” on connectors?

I've seen a few connectors with "kinked shell stakes" (example). It's probably obvious but what are they for? Are they somehow soldered to the board or do they wrap around it? Should I drill holes ...
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1answer
79 views

Experimental calculation of dc motor resistance

I am trying to calculate resistance of DC motor experimentally. I have measured voltage and current for different voltages applied (from -5V to 5 V). Motor shaft is blocked. And the question is why ...
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1answer
73 views

Shift in energy levels of transistors

As I was reading basic electronics, PN-junction diodes and two terminal MOSFETs, I understood the position of the fermi energy level and position of valence and conduction band in those devices. But I ...
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2answers
189 views

Will a 12v 2000mAh battery overpower(and damage) a 1.2a DC motor?

Sorry if this is Electrical Engineering pre-school. I'm a software guy that hasn't taken a class involving voltages for 10+ years. I'm working on an Arduino project that will have to be fairly ...
9
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4answers
2k views

ATMega8: why do VCC and AVCC have to be connected?

I often read that it is good practice to connect VCC with AVCC. Even in the ATMega8 datasheet it says so: AVCC is the supply voltage pin for the A/D Converter, Port C (3..0), and ADC (7..6). It ...
2
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1answer
70 views

How do I simplify this circuit to find resistor voltage?

In my circuits class, I am presented with the following exercise. simulate this circuit – Schematic created using CircuitLab The problem is to find the voltage across resistors A and B. ...
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6answers
1k views

Do electrical devices “take what they need”

One concept of electronics I have a hard time understanding is if things like motors, actuators, solenoids etc. use as much power as they need or what you give them. If a motor needs 12 volts and ...
2
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1answer
108 views

Current mirror Configuration using BJT application

I want to design a circuit having output voltage of 3.3 V and 30mA current. As I am newbie in the electronics field, I see lots of circuit using buck topology, using IC's and using transformers. Now ...
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2answers
160 views

Doubt on ground reference of Isolation transformer

I studies the posts on this blog regarding isolation transformer and its working. But I don't understand that when there is no ground reference in the secondary winding of the isolation transformer, ...
0
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1answer
241 views

How can I trigger a photography strobe from a iPhone LED flash?

I would like to trigger a photography/studio strobe flash based on the flash of an iPhone camera's LED flash. I'm picturing a device that I could attach to the back of the iPhone temporarily when I ...
0
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2answers
113 views

Should I supply a motor with the same current of its stall speed?

I have a DC motor that has a stall speed current of 6 amps. Does that mean I should be supplying a constant current of 6 amps even when the motor is not experiencing a need for that much current?
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7answers
3k views

Can a circuit be powered from Earth with a return ground on Mars?

Could you use a hot wire (120v 60 hz) from earth and a copper rod inserted into another extraterrestial body (mars) to complete a circuit? If impedance wasn't something to worry about (pretend Mars ...
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2answers
368 views

Why switching cause EMI & noise problem?

I was reading an article topic on "Selecting the correct IC for power supply applications" in which it tells the different types of topology and their pros and cons.In that, it list out the three ...