Fundamentals of electricity, electronics, components, or theory
0
votes
1answer
32 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
38 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 ...
0
votes
1answer
57 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
220 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
50 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. ...
13
votes
6answers
924 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
50 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
votes
2answers
85 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
89 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
84 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?
46
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
168 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
48 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
votes
1answer
130 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
71 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 ...
0
votes
1answer
285 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
90 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
71 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
183 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
186 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
109 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 ...
3
votes
6answers
252 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
45 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
174 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
115 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
118 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
106 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
475 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
votes
2answers
80 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 ...
-4
votes
1answer
127 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
294 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 ...
-4
votes
1answer
201 views
how to convert radio waves to some small DC power? [closed]
Is it possible to generate a small DC power from Radio waves?If yes then how?
0
votes
1answer
38 views
KVL equivalent versions
How do the first two statements (quoted below) logically correct when the third is viewed as voltage drops are only across resistors and the voltage rises are only across voltage sources? Where is the ...
2
votes
2answers
371 views
Using a transistor to add to max current output from a opamp?
I thought I understood transistors but now I'm confused again.
I have a basic opamp circuit to amplify the input of a electret microphone. The output of the opamp will vary within 1-4V. Now I want ...
4
votes
3answers
615 views
How to amplify electret microphone to range from 0-5V with bias of 2.5V?
I'm new to op amps and have tried many circuits but don't get the results I expect. I know I must do some math but I get so confused. I thought my question is really simple but it turns out it's not.
...
6
votes
3answers
253 views
Transistor Toggle Not Working
I'm trying to learn about how transistors work. As a simple test I created the following circuit:
My idea is that when the second transistor will keep the first one active after I click the button ...
3
votes
3answers
221 views
How to electronically generate exponential and logarithmic functions
i mean, it is possible to generate with Op amps, or diodes, etc, to generate complex exponential and logarithmic functions, like one can create sinusoidal signals using a Wien bridge oscillator.
...
2
votes
1answer
178 views
Calculating current in a simple circuit
I am new to electronics and am trying to figure something out:
I have a source putting out 12.6V and an unknown current.
I know that I can calculate current by finding the voltage drop over a ...
3
votes
3answers
147 views
Controlling LED with microphone input
I know this is an extremely simple question, but I haven't been able to figure this out on my own. I'm trying to get an LED to get brighter as ambient sound rises. What I've come up with: use a ...
4
votes
1answer
332 views
Basic rules to calculate the equivalent resistance of a resistor circuit
I have a certain circuit only containing resistors of different values. There is one 'input' and one 'output' for the current. How do I calculate the equivalent resistance of the circuit? Are there ...
0
votes
3answers
150 views
Op amp design that gives \$V_{out} = -2 *V_{1} + 3*V_{2} - 3 V_{3}\$
I know that a regular summing amplifier does \$\ V_{out} = -(a*V1 + b*V2 + c*V3)\$ but how do I invert one of the gains?
3
votes
2answers
260 views
Grounding in circuit diagrams
Often I see in circuit diagrams that the circuit is connected to the ground:
I understand that this creates a reference for zero potential, but why does all of the current not simply flow right ...
3
votes
4answers
382 views
Early Effect, Ebers-Moll, Common Emitter Resistance, reverse alpha/beta and saturation current
Ive been reading Sedra/Smith's Micro Electronic Circuits book, and it has a lot of info which I like, however I dont know how much of it is actually practial and useful, for instance it talks about ...
1
vote
1answer
113 views
How to choose an external powersource with electronic logic [closed]
I am a n00b in electronics (software developer)
I have 2 batteries bat1, bat2 (1.5 volts) available to me. I can only use one battery in my circuit. Let's say that if the battery is put in a holder ...
-8
votes
2answers
117 views
(Need help ASAP!) Electric motor bike with BASIC Stamp [closed]
We're doing the project is to develop an electric motor bicycle to assist the bike rider going up steep hills. In our project, we modified a bike with combination of electric motor, goniometer sensor ...
2
votes
3answers
4k views
How does current flow through a voltage source?
Im going back to electricity 101 to understand several things Im missing. One of them is exactly how does current flow through a DC source.
Heres my understanding: A voltage source is one which has ...
3
votes
3answers
351 views
Fundamental question about circuits and grounding
I understand that voltage is relative and that the hot wire in house mains is a nominal \$\pm\$ 120v in reference to the neutral wire. I also believe the ground wire is connected to the neutral at the ...
0
votes
1answer
88 views
which battery will supply the load?
I have connected 14V supply terminal from alternator to 12V battery terminal and has taken the load across these terminals . But the load is operating still in 12V, and when measured across the ...
0
votes
2answers
149 views
Intro Circuits Class Inductor question
This is a question from my intro circuits class that I can't figure out the answer to:
Of course it's very simple, but I had a professor who was incomprehensible most of the time, and my textbook ...
2
votes
4answers
216 views
Overload protection for battery
My 6-year-old son has shown some interest in electronics, and I thought I'd get him some basic components (motors, LEDs, buzzers, etc) and let him experiment (using alligator clips and the like -- no ...
