Electrical Engineering Stack Exchange
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1500 questions
66
votes
5 answers

How to choose value of resistor in voltage divider?

I understand that the output voltage is determined by the ratio between the two resistor values, and that if the both resistors are same then output voltage will be exactly same for all; but what's the basis of picking the resistor values?there is…
Coldblackice
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66
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4 answers

What do the PCB markings mean?

On a printed circuit board, I see lots of tiny letters and numbers. Is there some kind of standard that dictates what letter indicates what type of component?
kinokijuf
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66
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4 answers

What's the purpose of two capacitors in parallel?

What's the purpose of the two capacitors in parallel on each side of the regulator in this power supply circuit I've seen similar setups in other similar circuits and can guess that it's related to one being polarized an one not, but I don't really…
Brad Robinson
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66
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9 answers

When to avoid using a breadboard

What are the cases where one should avoid using a breadboard? e.g. high frequency, noise prone circuits etc.
stbtra
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66
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7 answers

Why is my circuit so incredibly sensitive to electric fluctuation?

I recently finished building a circuit showcased in a beginner’s electronics book. I have included the picture of my creation below because I think it may become relevant to the question. At the beginning of the build process, the instructions…
T555
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66
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4 answers

How to choose a flyback diode for a relay?

A diode is put in parallel with a relay coil (with opposite polarity) to prevent damage to other components when the relay is turned off. Here's an example schematic I found online: I'm planning on using a relay with a coil voltage of 5V and…
Nate
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65
votes
4 answers

Does mAh measure how long a battery would last?

I know mAh tells how much milliamperes a battery can deliver in an hour. But does that also tell how many hours the battery would last? Sorry but I don't really get it. If we're talking about a water tank, to my impression, mAh is like how big the…
supertonsky
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65
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9 answers

Why can't two series-connected diodes act as a BJT?

Another form of the question is: will joining two diodes with wires (pn-np) make a transistor-equivalent? I read that they are not equivalent, but why?
user23564
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65
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5 answers

What's the use of a decoupling capacitor near a reservoir capacitor?

I've seen some circuits where a decoupling capacitor is used as well as a reservoir capacitor, like this (C4 and C5): I've read about decoupling capacitors and for me it looks as if they are meant to remove small fluctuations in the supply voltage.…
user17592
65
votes
4 answers

Can I replace all electrolytic capacitors with ceramic?

I am designing the power supply circuit for a system that needs several supplies, my questions are: Is it possible to replace all electrolytic caps (Mostly 100uF) by ceramic ones? What are the limitations of ceramic? Should I use a 2x voltage…
Abdella
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65
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5 answers

What is impedance?

This is presented as both a resource for the community and a learning experience for myself. I have just enough knowledge of the subject to get myself into trouble, but I don't have the best grasp of the subject's details. Some helpful responses…
Jesse
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65
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9 answers

Fan and heatsink - suck or blow?

This question covered it for enclosures. However, from the point of view of the fan attached to a heatsink does it matter whether air is blown through the fins, or sucked through the fins. In other words, is the pattern of airflow different enough…
Dirk Bruere
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65
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3 answers

What is a boot loader, and how would I develop one?

I've met many projects in which an AVR microcontroller uses with a bootloader (such as the Arduino), but I don't understand the concept very well. How can I make a bootloader (for any microcontroller)? After writing my bootloader, how it is…
mina_g
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65
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8 answers

Why are there so many relays used in a car, instead of transistors?

Recently I did some work on my car electric circuits. I see many relays are used in car circuits. These relays are used for simple switching, and I wonder why these circuits are based on relays and not on transistors or other electronic components…
Al Kepp
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65
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12 answers

How can we be sure that computers will never accidentally switch a 0 by a 1?

I've read a bit about the construction of a digital computer in Shocken/Nisan's: The Elements of Computing Systems. But this book says nothing about certain electrical aspects in computers, for example: It's often said that 0's and 1's are…
Red Banana
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