Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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1500 questions
26
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8 answers

How to tell if chips overheat while soldering

I am new to soldering and I am afraid that I am getting some of my chips too hot. I'm sure this will be less of an issue when I get more experience. I also ordered some DIP sockets but they won't arrive for a few months. In the mean time is there…
MrMobius
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Making a battery last a long time in a microcontroller circuit

I'm hoping to power an ATtiny85V for a nice long time on some small battery, probably a coin cell. I've looked into the software side, and my code is watchdog timer driven, has unused analog and digital converters turned off, the chip is running at…
Jack Schmidt
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6 answers

PCB Design: Strange 'whiskers' from PCB pads?

Regarding the attached PCB image, you'll notice that there are odd 'whiskers' from PCB pads. I'm curious as to their purpose. The board isn't high frequency, so I doubt it's for any fancy RF-magic. My best guess is that because it is a home-etched…
M1GEO
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5 answers

How do I solder headers so that they always stand straight up?

When soldering headers, usually single and double pins, I flip the board over so the pin rests on the surface and then solder them. They never come out straight. It would be great if someone has figured out how to do this correctly?
Bill
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3 answers

Why do we use polarized capacitors?

I want to know if the polarized capacitor has some advantage that they are used in some circuits? For example, in a schematic of the BISS001 PIR controller IC, in some places, a polarized capacitor is used and in some places a non-polarized…
Hamid Mousavi
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26
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3 answers

Help identify the IC manufacturer: is it really possible that these ICs from the 60's just made a comeback (К155ИД1)?

So we've been manufacturing Nixie Clock kits for the last few years, and for the multiplexers we used 74141 ICs, or their Soviet clones (К155ИД1). The latter were easier to find on ebay and were used more commonly. These chips have a date code like…
anrieff
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6 answers

Why do high-voltage transformers need oil?

Someone told me that high-voltage transformers need oil because it prevents arcing. However, in terms of dielectric breakdown, isn't air the strongest? I remember from classes in college that as the dielectric constant increases, the breakdown…
PJazz
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4 answers

Why does an LED have to be a diode?

I know LED stands for Light Emitting Diode; but why does this component need to be a diode to emit light? My question assumes that the "leds" we see everywhere (for lighting, screens, etc) are actually diodes -- this assumption might be wrong.
noamtm
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26
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3 answers

What's special about "unity-gain stable"?

As mentioned in opamp datasheets, like this one. I would think stability is a problem at higher gains, due to oscillation. What are the problems with unity-gain?
Federico Russo
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26
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6 answers

Normal capacitor vs. audio capacitor

I'm building a power supply for old Schoeps CMT30F microphones. Standard condenser mic are 48V-powered nowadays, but these are 60s/70s Schoeps mic from RadioFrance/ORTF, customized at that time to be -9V or -10V powered. I need to add capacitors to…
Basj
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6 answers

Why does voltage always lead current by 90 degrees in an inductor?

I have learnt that in an inductor voltage leads current by 90 degrees. However, I do not fully understand why it is 90 degrees. I have been looking everywhere for more information on why this is so. However, all the sources I found just state the…
Roo
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26
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2 answers

Level shifting a +/- 2.5V signal to 0 - 5V

I have a front end module that generates an (ECG) signal that varies from +/-2.5 V. I want to shift this signal to 0 - 5V. What is the best way to do this? Would a summing amplifier like the below circuit good enough? With R1 = R2 and V1 = 2.5V, V2…
govind m
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26
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5 answers

Just chopped a cable, is red power, black ground?

I've just chopped a usb to micro-b usb cable. There are 4 small wires inside Red Black White Green Isn't it universal that Red is power and black is ground?
Jason94
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6 answers

Is it OK to route a trace through a pad?

Will I have any trouble routing the traces in this way? (VCC and GND) Is it OK considering that the entire circuit current is under 50mA?
Lucas Alexandre
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FCC part 15 "must accept interference from other sources": what does this mean?

I've googled around a bit and here are the interpretations I've found in non-authoritative sources: that the device is unable to filter out interference caused by other certified equipment that if there is interference, the device must not…
Roman Starkov
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