Electrical Engineering Stack Exchange
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1500 questions
67
votes
8 answers

Why do we need an isolation transformer to connect an oscilloscope?

My professor always insists that I provide power to an oscilloscope thorough an isolation transformer. What is the necessity of this? What is the risk if I don't connect it?
noufal
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67
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3 answers

How do I identify SMD components? (or how do I identify any component)

How do I identify the markings on an SMT component and match it up with a part number so I can be a good designer and actually look at a datasheet (and read the whole thing)? Or identify a part to replace an unknown part on a PCB?
Voltage Spike
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67
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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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67
votes
3 answers

Why is kerosene stopping my red LEDs from illuminating?

I initially posted this on chemistry.stackexchange but didn't get any answers, so I'm reposting it here. Long story short - we have an electronic product that is submerged in fuels (kerosene being one of them) and uses an RGB LED (click here for…
Amr Bekhit
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67
votes
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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67
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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
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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66
votes
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
66
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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66
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1 answer

Duracell PowerCheck - How Does It Work?

I've been using these batteries for a long time and I've never seen such a feature. There's a band on its outer wrapping having two ends: The white circle on the left side and the another one on the right side (not visible because it's under my…
Rohat Kılıç
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66
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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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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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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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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 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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