Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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1500 questions
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5 answers

How do I design my very own ARM based processors?

I have several questions about how I would design my own ARM-based CPU? How does one start with an ARM license and end up with a package ready to be soldered on to a board? What do I get from ARM (I am sure they have multiple license options to…
Lord Loh.
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Why does an antenna trace have this shape?

I'm wondering why an antenna has a board trace that follows a certain "squiggly" shape. This doesn't have to apply to only antennas; I'm sure that there are other components that have changing paths for various reasons, but the antenna usually…
Ci3
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20 answers

What is a good microcontroller for Ethernet applications?

What is a good microcontroller for doing Ethernet applications? Or do I just need a good Ethernet library to connect with an Ethernet MAC/PHY?
Robert Deml
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47
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11 answers

Cheapest FPGAs?

How cheap do FPGAs get? I know they're more expensive than microprocessors of comparable capability, but I wonder if there exist FPGAs that could contain a Microblaze soft core running Linux, while leaving gates available for implementing DSP…
pingswept
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47
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6 answers

Is there a technical reason why most touch screens use glass rather than plastic?

Most modern touch screens in portable devices are made of glass. This glass often breaks if accidentally dropped. Also, it is very reflective, making it difficult to use in strong light. I know that touch screens without glass exist. For example,…
Fiksdal
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11 answers

Is there a dual of the transformer?

Capacitors and inductors are duals of each other. A transformer is made of two inductors, and transfers power through mutual inductance, through the magnetic near-field (right?) Also, you can vary the ratio of voltages or currents by changing the…
endolith
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5 answers

Is the neutral wire considered safe?

If the neutral wire carries current, why do many people believe that it's safe? I've heard "You can touch the neutral wire/bar in the breaker box and not get shocked. Only the hot can hurt you." If the circuit is complete and current is flowing,…
Stephen Melvin
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3 answers

What are these "dogbone" traces for on (1970s era) PCB?

I've been spending some time with some old PCBs from the 70s. I have seen this pattern on some, which are these short traces that appear as little whiskers in between each of the IC lead/leg through-holes. (This pic is obviously unpopulated.) They…
BZo
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46
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8 answers

Why are relays so frequently driven by optocouplers?

Since the advent of the many microcontroller development boards, like Arduino, there have been a number of relay modules sold to drive mains AC loads. A lot of these seem to use an optocoupler, driver transistor and a relay to drive the load…
Cybergibbons
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5 answers

Why would an op-amp use BJTs over MOSFETs?

I've always been told that ideally, op-amps have infinite input impedance. So when I was looking at the LM741's transistor level schematic, I was confused when they used BJTs instead of MOSFETs. Wouldn't using a BJT result in current flowing into…
Nate
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46
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8 answers

USB Shield. To ground or not to ground?

I have been given a device at work to do some testing on. Basically an IC is becoming obsolete so I need to test a replacement part. Upon redoing the ESD checks, the device failed. I checked the history of the device, and there were problems…
MCG
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46
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4 answers

At what voltage is a NiMH battery empty?

I have a battery pack of NiMH batteries. It is ten cells with 1.2V, 4000mAh each, put together in series. So rated voltage is 12V. After charging, i.e. when the charging device says that it is finished, I measure 14.3V. When I now discharge, at…
Till B
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46
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6 answers

Why aren’t the main conductors in this underground power cable made from copper?

I’ve found a piece of electrical cable left by the electricity company that supplies the area. They did a repair recently underground. I’m curious why the three big triangular conductors aren’t made from copper. It looks like aluminium to me, but…
i-CONICA
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2 answers

How is ASIC design different from FPGA HDL synthesis?

I've had some experience with FPGA/HDL tool suites such as Xilinx ISE, Lattice Diamond, etc. The general workflow is writing Verilog/VHDL, simulation, testing and then programming the FPGA. I've heard a couple of people say ASIC design is very…
Robin Rodricks
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2 answers

What's special about 14.31818 MHz?

While desoldering useful components off of old computer hardware, I found quite a large number of 14.31818 MHz crystals. This seemed odd to me. Why use such an irregular frequency with a very nontrivial conversion to human time units? At first I…
FlashCactus
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