# Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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### 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 ...
4k 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 ...
8k 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?
521 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 into ...
348 views

### EE for Software engineers [closed]

Recently I've started playing a lot with 3D printers, Adrunio, Pandaboards and Kinect's SDK. I'm starting to have more and more passion for this sort of devices and I think it's about to turn into a ...
1k 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 ...
154 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 ...
48k 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 ...
1k 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 ...
103 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 ...
221 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 ...
1k 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 ...
8k views

### Designing a cable tester

I need to check the integrity of 40+ custom cables. Each cable is meant to be the same, and is meant to have 19 ways. I bought an enclosure, some mating connectors, some LEDS and a bunch of ...
9k views

### How to wire a GSM module to my alarm system

I have an alarm system that has been installed by an alarm dude ;) I want to add a GSM module to the alarm system, so that I'm notified when the alarm is triggered. Before I purchase the module I ...
608 views

### Capacitor discharge and 1/2 terminal voltage sources

I understand that this is really basics of electronics, but I would really appreciate if somebody clearly explained following question. So here is a small set of questions related to similar topic: ...
3k views

### Where can I find beginners electronics project schematics online, for free? [closed]

I have bought the following books in order to start learning basic electronics: Electronics All-In-One Desk Reference For Dummies Robot Building for Beginners (Technology in Action) My desire though,...
7k views

### Why voltage lags by 90° from magnetic flux?

I was not sure if I should write it here or on Physics board, but I will give a try. As I understood current (generally emf) can be generated in a system by varying magnetic flux. For example, let's ...
942 views

### Basic nature of electric current/voltage

I'm curious about electronic/electric. I just want some visual, easy to understand explanation/depiction about basic nature of electric current/voltage, relations between them, why electrons make a ...
34k views

### How can I learn electronics at home? [duplicate]

Possible Duplicate: Learning about electronics I am 40. I am an architect by profession. I am very interested in learning electronics. I don't have time to go to college for an electronics ...
6k views

### What's a good way to start learning how electronics and circuits work? [closed]

I literally already tried getting a degree in Electrical Engineering, and I hated it, and I switched to Computer Science. But here's the thing-- I find circuits and electronics and electrical devices ...
6k views

### What is Normalized DC Current Gain (as oppossed to DC Current gain)?

I have a table that presents DC Current Gain for BC548B transistor: and a graph that presents Normalized DC Current Gain: Are those two things related? What does "normalized" mean? Why is the Y-axis ...
39k views

### How electrons inside copper wire behave when source is ac or dc?

When a simple copper wire is connected to AC or DC, what actually happens to the electrons inside the wire? I.e. What kind of path do they follow when they reach the end of the wire? If anyone can ...
14k views

### Electronics course - From basics to designing circuits [duplicate]

Possible Duplicate: From zero to “almost pro”: Newbie trying to learn. Good, quick resources? What good resources are there for a high school student to start learning electronics? I am trying to ...
569 views

### Where can I learn about how to create homemade electronics

Unfortunately, all I've learnt so far are concepts. I do not know where to start, but I have made a commitment to practically build some electronics. I want to ask where can I learn and acquires the ...
356 views

### What is the impedance of this unusual (magnetically coupled) circuit?

Inductors X1 and X2 are magnetically coupled M = 20 [Ohm] X1 = 20 [Ohm] X2 = 30 [Ohm] I am not sure how to interpret short circuit. Is the circuit impedance given by the equation: _Z = R1 + jX1 + ...
12k views

### What is the voltage divider rule?

Can anyone explain what the voltage divider rule is? How has the author of this book used it for analyzing the Voltage Divider Bias circuit for transistors? And can anyone explain how the two ...
57k views

### Why should a circuit be grounded?

Why should a transistor circuit be grounded? The way I understand it is that ground is an infinite supply of electrons and so it is equivalent to the negative terminal of a battery. But in this page , ...
12k views

### How does this SIM card reader circuit work?

The circuit for a SIM card reader is shown here. The circuit uses a CMOS hex inverter and other simple components; yet, not only does it work but it can also communicate with a PC via serial port! I ...
12k views

### Why is the Ampere the only SI fundamental unit for electricity?

According to wikipedia the only SI fundamental unit for Matters Electrickal is the ampere. Don't you at least need the ohm to derive anything? How would you make volts from only amps? Perhaps I ...
12k views

### Principal of Analog to digital converter(ADC) and Digital to analog converter(DAC)

Analog to digital converter is one that converts analog output form sensors to digital one what are basic principal of Analog to digital converter(ADC) and the opposite of one that takes digital input ...
3k views

### What are analog and digital signals?

I came across the concept of analog and digital signals in my data communication course. We studied that analog signals are continuous signals and teacher presented a diagram like the sine wave and ...
5k views

### Path for a child to learn electrical engineering

What are some paths for a child (7-year-old) to learn electrical engineering (in a safe way)? I do not want to saturate (or frighten away) the child with lots of concepts, I want that my son learn ...
32k views

### How does an astable multivibrator LED blinking circuit work?

I am a beginner in electronics. I come to know about the oscillator using RC circuits (capacitor charge and discharge and time constant tells the behavior of circuit). Then I saw the following ...
4k views

### Why we need to complete circuit

Why can't we light an LED with a single positive wire on the anode, leaving the cathode unconnected? Let's suppose I connect a wire with a positive voltage to the anode of the LED. Now, I think, ...
4k views

### Low pass audio filter design

I want my Arduino project to listen to the ambient music and sync its light show output to the beat. It seems that doing BPM detection properly is fiendishly difficult in software, but if your music ...
7k views

### What is an amp (and other such basic questions) in the simplest possible terms?

I understand that this is a really basic question, but, I've been unable to really understand electrical terminology for some reason. What exactly is an amp? How does it correspond to a watt? And: ...
4k views

### Learning about electronics

I'm a computer scientist with zero exposure to things directly related to hardware (barring what I learned from my undergrad computer org class.) I've been very attracted to the field of embedded ...
4k views

### Transistor with two voltage levels, Vb ≠ Vcc

Why is my transistor only driving 5V instead of 6V? How can I fix it? I have a 6V, 25mA circuit running some LEDs. I can control them by connecting and disconnecting the positive terminal of the ...
3k views

### From zero to “almost pro”: Newbie trying to learn. Good, quick resources?

I am a total zero in electronics. I just know what is a resistor and what is a capacitor. I also know what is a 555 just because I've been told what it does, 15 years ago. Apart from this and a bunch ...
36k views

### How do I connect two identical batteries to increase the consumer lifetime?

If I've got a device that uses a single battery, and with that single battery, the device lasts an hour, and I want the device to last for two hours, I'm assuming I can wire two batteries up and it ...
3k views

### FTDI Basic Breakout - 5V

Can this board be used to upload sketches to the Arduino. I tried by hooking the TX port on the FTDI Basic Breakout to RX port(Pin 2 on the Arduino) and RX port to pin 3 on the Arduino. But so far I ...