Most Popular
1500 questions
43
votes
9 answers
How to hold SMD parts in place while soldering?
I go through this every time I have PCBs I need to populate with SMD parts, and this has become more an issue as pin spacings have gotten tighter, and my hands have become less steady with age.
So far I've modified some curved tweezers with a…
Randy
- 3,245
- 3
- 22
- 39
43
votes
1 answer
What do you need 1.018V for?
The Fluke 732A has among 10V and 1V references also a 1.018V reference (whereas the 10V is the "main" references and the others are formed by resistive voltage dividers).
While having multiple reference voltages is surely convenient, why exactly…
PlasmaHH
- 6,528
- 5
- 38
- 49
43
votes
5 answers
Why use complex numbers to represent amplitude and phase of AC
Why is it that in AC circuits, sine waves are represented as a complex number in polar form? I don't logically understand from a physical perspective why there is an imaginary part at all. Is it purely from a mathematical point of view to make the…
Prevost
- 603
- 2
- 10
- 16
42
votes
3 answers
How do Circuit Simulators actually work?
I recently had the opportunity to play around with LiveWire, which is a circuit simulator and began wondering how exactly they computed the voltages across each component and the current going through each track of wire.
I have only been taught…
Thomas Russell
- 1,156
- 2
- 9
- 21
42
votes
1 answer
What to do with third contact in DC barrel plug with only two input contacts
My AC-DC adapter gives output of 12V and GND. I tried to search for suitable DC barrel plugs
and found that most of them have three terminals
So, pin 1 is positive in my case.
1. Which pin should I connect to GND, 2 or 3, in my PCB?
2. What should…
zud
- 887
- 3
- 9
- 14
42
votes
2 answers
My scope detects a 50Hz signal when the probe is not connected to a circuit, is this normal?
Having no prior experience with scopes, it seems strange to me that when the probe is not measuring anything (~ not connected to a circuit) it measures a small 50Hz (~ my mains are running at 230V 50Hz) signal instead of some random noise. Is this…
damd
- 523
- 1
- 4
- 5
42
votes
8 answers
What is a pull up and pull down?
Can some one explain this terminology please I think I understand it but not completely sure.
I think pull down is where you place a resistor between +V and the other component and pull up is where you place the resistor between 0v and the…
Dean
- 8,448
- 27
- 72
- 120
42
votes
3 answers
Sizing MOSFET gate resistor
I have an N-MOSFET gate connected to a 4043 logic. Id is about 100 mA. Both the 4043 and MOSFET have +5 V. I plan to use a 2N7000.
How large a gate resistor do I need between the 4043 and MOSFET? The logic output is sometimes switched rapidly. How…
hanukas
- 423
- 1
- 4
- 5
42
votes
3 answers
How does an electronic caliper work?
How do these electronic calipers work?:
I know they work by measuring the capacitance of the running track, somehow. But how do they use capacitance to measure distances - is it a linear relationship of capacitance to distance, or is there…
Thomas O
- 31,786
- 58
- 184
- 322
42
votes
2 answers
What is a "DIE" package?
In a list of ICs, along with the familiar package names such as QFN32, LQFP48, etc., I've seen a few ICs to be listed as DIE for the package size. I've never seen that description before as an IC package size, and Wikipedia does not list it…
vsz
- 2,564
- 1
- 18
- 35
42
votes
1 answer
What is / how can I get a student-safe power supply for electronics projects?
What is / how can I get a student-safe power supply for electronics projects?
I'm looking for a student-safe power supply for solder less breadboard. I'm developing a course to teach electrical engineering to grade school students as an…
JJ Rohrer
- 529
- 3
- 7
42
votes
5 answers
Who receives the value returned by main()?
I know that in computers, value returned by the main() function is received by the operating system.
But, what happens in the main() function of a microcontroller?
user18118
- 551
- 1
- 5
- 5
42
votes
4 answers
Solder does not stick to tip of soldering iron?
Basic question here, but it's driving me insane!
The solder does not seem to stick to the tip of my soldering iron. After the iron heats up, the tip appears black (sometimes on all sides and sometimes on one side), then either it doesn't melt the…
user13267
- 621
- 2
- 10
- 24
42
votes
3 answers
Does Bluetooth interfere with WiFi?
I've read that WiFi b/g/n is using 2.3995 to 2.4845 GHz.
Bluetooth is in between: 2.4000 to 2.4835 GHz.
So what will happen when I put a Bluetooth sending device next to a WiFi sending device?
Will the two devices be aware of each other (like two…
zomega
- 609
- 1
- 6
- 11
42
votes
10 answers
Do dead weight 'components' exist?
After making a prototype circuit board, I usually glue four rubber pads/bumpers to the bottom, to keep it stable on my desk:
Unfortunately, my boards are usually too light. When connected to a few cables, they float around to wherever they're…
K.Mulier
- 2,359
- 4
- 23
- 40