Fundamentals of electricity, electronics, components, or theory

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0
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1answer
71 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
91 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
66 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 ...
29
votes
10answers
2k 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
52 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
450 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
234 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
110 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
41 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
68 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
121 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
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2answers
63 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
85 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
101 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
votes
6answers
2k 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
82 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
96 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
votes
1answer
118 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 ...
1
vote
2answers
80 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 ...
0
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1answer
65 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 ...
1
vote
1answer
66 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 ...
1
vote
2answers
143 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
votes
4answers
1k 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
votes
1answer
63 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. ...
15
votes
6answers
989 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
votes
1answer
92 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 ...
-1
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2answers
141 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
votes
1answer
202 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
votes
2answers
104 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?
48
votes
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 ...
2
votes
2answers
271 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 ...
0
votes
1answer
80 views

How can I find maximum power transfer using Thevenin equivalent

As I understand it, should maximum power transfer be when $$ R_L=R_{th} $$ then $$ P_L= P_{L(max)} $$ So that this should do the trick: $$ P_{L}=\frac{V_{th} ^2}{R_{th}} $$ But it seems that I ...
0
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1answer
365 views

wattmeter average power

Average power can be measured by wattmeter, so why in the attached example it doesn't function properly- doesn't show 0 W?
-2
votes
1answer
81 views

transformer's basic operation

Doesn't the induced voltage (v1) suppose to oppose i1 flow, so + and- should be inverted? Is it possible for the same transformer that v1/v2=-a and i2/i1=a (for example if it is possible to ...
1
vote
1answer
602 views

Selection parameters of a X & Y rated capacitors

In a capacitor drop supply, X rated capacitors are responsible for dropping the AC voltage across them. I've been looking at why only X rated capacitors are used. After spending some time searching ...
3
votes
2answers
134 views

autotransformers currents

Why is the 5A at the 10 000V winding is directed upwards? Is that because of Lenz's law? Edit: Given a 50kVA power transformer that has a voltage rating of 10000/200 V, I know that the high voltage ...
0
votes
2answers
93 views

full load primary and secondary currents of a transformer

Why does the question mention "full load currents", what if there isn't such currents, would the transformer function differently? What are the full-load primary and secondary currents of a ...
0
votes
1answer
276 views

Importance of removing ripples in output of dc-dc converter

I heard from somewhere that for some power supplies, it is important that there be no ripple and 'dips' in the output of a constant voltage output dc-dc converter. The specific cases are: 1.) When ...
1
vote
3answers
205 views

How bad can an unconnected ground be?

My collegue here has two seperate boards linked by an SPI link. He just asked me: "So... you need to connect the grounds?" After I picked myself off the floor and answered very much in the ...
2
votes
1answer
118 views

Static electricity discharge, what gets transfered?

Ive been studying Maxwell equations at school and I solved several excercises regarding electrostatic fields, however I still have some very basic unanswered questions: When a non conductive object ...
4
votes
7answers
338 views

Decrease in stored energy after connection of another capacitor

A 3-µF capacitor charged to 100V is connected across an uncharged 6-µF capacitor. So the initial stored energy is: 15mJ and the final: 5mJ. What happen to the 10-mJ of energy?
2
votes
1answer
74 views

Trigger switch using basic components

I am doing a project at a local fair which is one of those 'steady hands' games. I am adding a twist that if you touch the wire with the loop you are dragging through it once, distractions will start. ...
1
vote
1answer
228 views

How to get started with electronics and specifically cheap microcontrollers? [closed]

I have a birthday coming up and would like to try and "get into" electronics. Now seems like the ideal time to finally get enough components to get started. However I need advise choosing what to get. ...
0
votes
1answer
172 views

Dependent sources

simulate this circuit – Schematic created using CircuitLab I had read about Thevenin's theorem that: If the resistors in part A are in parallel-series configuration, the Thevenin ...
0
votes
2answers
134 views

“8 LED Fun” for Arduinos explained?

I'm relatively new to programming, Arduinos, and online forums in general. I would really appreciate an explanation for one of the basic tutorials for Arduinos: I connected 8 LEDs to 8 pins (2 ...
3
votes
1answer
112 views

Use of current division

"Calculate V (across the current source) and the current flowing down through R1." simulate this circuit – Schematic created using CircuitLab Does the voltage source also produce current, ...
1
vote
4answers
1k views

Can I determine the original resistance of a burnt/failed resistor?

How to find the (original) value of a burnt resistor? Let's suppose a condition in which initially I don't know the value of its resistance. Now because of its low watt, it burnt. So is there any ...
0
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2answers
111 views

Meaning of negative voltage

When solving for circuit consists of ideal voltages and conventional resistors I get that one of the resistor's voltage is negative- does it mean the resistor delivers power, or the polarity of the ...
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1answer
163 views

Application of SCR & TRIAC in electronics Field [closed]

What are the main applications of an SCR in analog electronics as well as in digital electronics? I only heard them in my books I have seen only usage of transistors, MOSFETs, FET's during the ...
1
vote
2answers
532 views

Double-Subscript Notation for Voltages

I have read from some book that: "The voltage quantity symbol V sometimes has subscripts to designate the two points to which the voltage corresponds. If the letter a designates one point and b the ...