Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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1500 questions
21
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7 answers

Ultrasonic Sensors and Pets

I've been eyeing using an Ultrasonic distance sensor for an upcoming project; either the Parallax Ping or the OSEPP Ultrasonic sensor (I think they are identical other than branding). Ex: https://www.parallax.com/product/28015 My concern is, this…
SnakeDoc
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Why does low frequency RFID have a short read range?

If I want to get the wavelength of a radio wave, I must divide the speed of light by the frequency? So having a 125 kHz RFID means an estimated 2km wavelength? If its wavelength is 2km long, why does this low frequency RFID have a short read…
Black
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21
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2 answers

Back-to-back MOSFETs: common source vs common drain?

If connecting a pair of discrete MOSFETs back-to-back to create a bidirectional load switch, what's the practical difference between having them common-source versus common-drain? In this particular case, I'm using a pair of p-ch FETs to isolate a…
JohnH
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21
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5 answers

How to safely dispose of a damaged lithium ion battery?

I replaced a lithium ion battery in a device and the old battery is swollen/bulging but no otherwise damaged. My municipality (NYC) requires many retailers to accept batteries or devices containing them but I am concerned that none of them can…
Kenny Evitt
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21
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4 answers

Can you stack SMD resistors in parallel to reduce power dissipation per resistor?

I sent my PCB a couple of days ago for fabrication but just realized a terrible error: I need to send 70mA to an IR LED with a 5V supply so I would need a resistor of about 70ohm, which means the resistor would be dissipating 350mW of power. The…
Shubham
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21
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5 answers

Can I use ST-Link programmer for non-ST chips?

Can I program all kinds of SWD-programmable chips (ARM-MCUs) with ST-Link?
Meylis Cherkezov
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21
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1 answer

SPI bus termination and pull-up resistors

My microcontroller (ATMEL series) needs to communicate to a slave device using SPI protocol. I am designing the hardware. The maximum SPI bus speed is 1 MHz. The distance between the master and slave is less than 50mm. Q1) Do I need to add…
Bharav
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21
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6 answers

Why are DC signals bad for loud speakers?

I googled and found out through some forum that: DC has a constant amplitude which overheats and destroys the voice coil of the speaker. Could someone clarify if this answer is complete and accurate?
Hilton Khadka
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21
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4 answers

Electronics System Standards Compliance: Certification, Testing & Verification

Please note: this question has to do with the technical compliance aspects of the consumer electronics indsutry, and as such, I believe is within scope for this site. This question is about compliance, and Compliance is absolutely a qualitative…
smeeb
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21
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6 answers

LTspice automation

I have a battery-powered boost converter and I'm attempting to measure the maximum input (battery) voltage droop under various load conditions of high current draws (different duty-cycles/periodicities) in addition to over several battery types…
Joel B
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21
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8 answers

STM32 & ST-LINK - Cannot connect to MCU after successful programming

I have built my own board with STM32F7-45VGT6. I have successfully programmed it with ST-LINK v2 (not the original one though) and now I cannot even connect with MCU. I use ST-Link Utility from ST and SWD interface. It can be the case that I use SWD…
zupazt3
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21
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9 answers

How can AC current power anything?

I understand the difference between AC and DC. What I don't understand is how does AC power anything when it's reusing the same electrons over and over as they are moving back and forth? A visual picture is this link at 0:35. Wouldn't it require…
Luke
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21
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3 answers

What value does ammeter or voltmeter measures (RMS, Average or Peak )?

What value does these meters measure? Is it RMS, Average or Peak value ?
Arun M
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21
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1 answer

PCIe, diagnosing and improving an eye diagram

I have implemented a design that uses PCIe. It is somewhat different in that the PCIe interface is used as a chip-to-chip communication lane on a single PCB (e.g. no PCIe connector). The root complex device is a Freescale i.MX6 which is PCIe Gen 2…
Funkyeah
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21
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2 answers

What's the main differences between a TSSOP and a SOIC and when would you use one over the other?

I was recently looking at some SPI SRAM chips at Mouser and noticed that a particular IC came in both a SOIC-8 and TSSOP-8 package. The specs seem identical but the price is different (not by much, but different). Visually, it looks like you could…
cbmeeks
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