Most Popular
1500 questions
50
votes
7 answers
What should a contract Electrical Engineer deliver once a project is complete?
I'm getting ready to hire an electrical engineer for a small contract job - creating a prototype. What I'd like to know is, what should I have him deliver to me when the project is complete?
I imagine schematics, the prototype, parts list would be…
Adam
- 253
- 4
- 5
50
votes
5 answers
Why is the voltage measurement of this circuit different when the switch is on?
I built a simple circuit with two lamps and a slide switch powered by two 1.5 V batteries. When the slide switch is off, the voltage of the circuit measured by a multimeter is 3.15 V:
However, when the slide switch is on, and the lamps are lit, the…
korppu73
- 741
- 6
- 8
50
votes
7 answers
230V AC to 5V DC converter, lossless
Is there any IC which converts 230V AC to 5V DC? As lossless as possible. I want to connect my microcontroller to an ordinary electrical socket and I don't have enough space available. Thanks.
arminb
- 1,622
- 4
- 21
- 34
50
votes
10 answers
Why hasn't my LED burned out by now?
I have a 15 year old ReplayTV DVR. I got it used, I'm not sure when, but probably about a decade ago. It's turned on almost all the time, and it has a blue power LED on the front.
The LED FAQ says that many LEDs have a rated lifetime of 50,000…
Barmar
- 689
- 1
- 5
- 7
50
votes
11 answers
Why isn't stripping wires by burning with a lighter a more common practice?
I see people suggesting specialized tools, or trying it manually with sharp knife or scalpel, why not just burning the rubber for a second or two with a lighter and just pulling it out a more suggested option?
Is there any con to this approach that…
appwizcpl
- 921
- 2
- 11
- 14
50
votes
4 answers
Why does hot plugging blow stuff up, and how to prevent it?
I made the very stupid mistake of hot plugging stuff many times before. My problem is that I rushed and it's just so easy for me to forget I have the Arduino on or some other expensive IC or hardware plugged in.
Today I hotplugged the PWM input of…
Ageis
- 3,311
- 13
- 44
- 67
50
votes
4 answers
Loud pop noise while plugging to a headphones jack
I have a Panasonic RX-ES29 boombox with a type C plug (ungrounded). I sometimes hear a relatively loud snap/pop sound in the right speaker of my headphones while I completely plug them into the headphones jack of the boombox when it's on. There's a…
Sepp A
- 563
- 1
- 4
- 6
50
votes
7 answers
How do I measure a negative voltage with a ADC?
I am working with a PIC micro-controller with inbuilt 10bit ADC and want to measure a voltage in the range of -1 to -3Volts.
I thought of using an op-amp in the inverting mode to make voltage positive and then feed it to the adc of the…
Kevin Boyd
- 1,971
- 4
- 23
- 28
50
votes
5 answers
Why don't microcontrollers generally have on-chip DACs?
In this answer I read that microcontrollers usually don't have DACs, while they do have ADC. Why is that?
edit
I appreciate that integrating resistors like in an R-2R DAC is expensive in terms of real-estate (thanks Mike, for your answer), but I…
Federico Russo
- 9,658
- 17
- 68
- 117
50
votes
6 answers
Easy way to figure out a LED's Vf in order to pick an appropriate resistor
I was wondering what the easiest way to figure out a LED's forward voltage is, using measurement tools. I know we can assume red LEDs to be around 1.8V - 2.2V, and that we have similar information for other LED colors, but I was wondering if…
diegoreymendez
- 657
- 1
- 6
- 10
50
votes
2 answers
STM32 Understanding GPIO Settings
In STM32 Standard Peripheral library, we need to configure the GPIO.
But there are 3 functions which I not sure how to configure them;
GPIO_InitStructure.GPIO_Speed
GPIO_InitStructure.GPIO_OType
GPIO_InitStructure.GPIO_PuPd
In the GPIO_Speed,…
Tim
- 899
- 2
- 12
- 18
50
votes
5 answers
Why aren't decoupling caps built into the IC or IC package?
The title is probably good enough, but I've always wondered why decoupling caps aren't built into the chip or at least the IC packaging?
kenny
- 955
- 10
- 14
50
votes
8 answers
How can I tell charge-only USB cables from USB data cables?
Like most computer hobbyists and programmers, I've amassed boxes of USB cables to connect USB, Micro-USB, and Mini-USB to chargers, computers, and gadgets. These cables are a mix of phone charger cables, and cables that came with external hard…
Benzo
- 603
- 1
- 5
- 5
50
votes
5 answers
How can a CPU deliver more than one instruction per cycle?
Wikipedia's Instructions per second page says that an i7 3630QM deliver ~110,000 MIPS at a frequency of 3.2 GHz; it would be (110/3.2 instructions) / 4 core = ~8.6 instructions per cycle per core?!
How can a single core deliver more than one…
davide
- 603
- 1
- 5
- 5
50
votes
3 answers
When a battery is your power source, what is ground?
For the sake of not incorrectly connecting my power supply and damaging my board I'm going to ask a relatively dumb question. Is ground on my board the negative terminal on my battery? Explicitly should I connect the ground to the negative terminal…
QueueHammer
- 719
- 1
- 6
- 9