Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [detection]

239 questions
37
votes
5 answers

Detecting light with an LED

How do I detect light with an LED?
mad_z
  • 5,050
  • 5
  • 45
  • 56
31
votes
7 answers

Smart ways to detect a button (less power consuming)

During a meeting for a particular project I was asked to think about the way to detect a push on a button with a MCU. The detection should consume as little power as possible. At the first glance, I thought the typical circuit with a pull-up or a…
vionyst
  • 846
  • 8
  • 16
20
votes
4 answers

How does an audio jack detect when a speaker is plugged in?

Some sound card audio jacks can now inform recent Windows OS's that an audio device is plugged in. Anyone know how it does this? I'm thinking it uses some kind of voltage comparator or resistance measurement. This question was asked at Superuser. …
user553
  • 303
  • 1
  • 2
  • 6
16
votes
4 answers

What are my options for detecting the position of a small moving metal object?

This is an airgun pellet trap: I fire small metal pellets at it (4.5mm = .177" in diameter) at up to 120 m/s = 390 fps. What are my options for detecting the X / Y position at which it enters the target? Does it make it easier if I only need to…
Tobia
  • 767
  • 6
  • 13
15
votes
5 answers

Making an electronic chess board

I want to make a wooden chess board that you can play on with regular pieces (i.e., not modified pieces that make use of RFID codes, magnets, …), but that is connected to a software that takes notice of my moves and acts as the second player. I have…
Golo Roden
  • 603
  • 1
  • 6
  • 16
14
votes
3 answers

What is a good approach to detecting distance and speed in model railroads?

Up front I must admit to little hands-on knowledge of modern microcontrollers and their software - I know power engineering and big motors much better (45 years of it). Now, my question: Trying to get grandchildren enthused about electronics. They…
Seemingly So
  • 592
  • 1
  • 4
  • 14
12
votes
6 answers

Detecting object placement on a grid

I am working on an Android ADK project. I am looking for a way to detect the locations of chess pieces on a board (8x8). I was looking at things like NFC but It looks too expensive. Is there a different technology that I should consider. I need…
theJosh
  • 223
  • 2
  • 7
11
votes
3 answers

How do network devices detect whether an ethernet cable is connected?

I have a bit of kit with an FPGA on it which includes an ethernet adapter. I'm trying to diagnose why it's not working and while I do that I've noticed that with an ethernet cable connected to my laptop, I see the network coming up and then dropping…
JonCage
  • 261
  • 1
  • 3
  • 9
11
votes
4 answers

How does a non contact voltage tester work?

How does a non contact voltage tester pen detect voltages and/or currents? Are they limited to voltages of a certain range or type (AC or DC)? Here's some experiments I have conducted that lead to this question: Using a cheap pen I bought for a…
JWVincent
  • 113
  • 1
  • 1
  • 5
10
votes
1 answer

Long range RFID detection

I have a question about detecting RFID tags at long range. I understand there are LF, HF,and UHF RFID frequencies. I'm looking to detect a tag from a minimum distance of 2 meters (actually, 5 meters if possible). I would really like to us HF chips,…
hwrdprkns
  • 203
  • 2
  • 7
9
votes
4 answers

Why the integral is zero

I wonder why under assumption that \$\omega \gg \frac{1}{T}\$ then \$\int_{0}^{T} \sin(\omega t)dt \approx 0\$? Since the integral should be like \$\frac{\cos(\omega t)}{w}\$ from \$0\$ to \$T\$ and after plugging the valued we will end up with…
user59419
  • 213
  • 1
  • 8
8
votes
2 answers

Detect aluminum using an inductive sensor

I was wondering if you can use an inductive proximity sensor to detect aluminum or if a capacitive sensor must be used? I wasn't sure if inductive sensors were reserved for ferrous metals only.
user337
  • 361
  • 2
  • 3
  • 9
8
votes
3 answers

Olimex Arm USB JTAG Programmer Problems

I've recently bought an Olimx ARM-USB-OCD JTAG programmer but I've had difficulty getting it to work. My primary system is linux, but I've tested it in window with no luck there either. I'm using OpenOCD to communicate with the device, but it does…
talex
  • 161
  • 1
  • 5
8
votes
3 answers

How can I detect when a signal becomes noisy?

I'm using a sensor to measure water potential. We record the output value every minute. Up until 4/16, the signal is pretty clean but I need some sort of way to detect when the signal starts to get noisy so that I can go check on the sensor. Link…
BiosphereEngineering
  • 83
  • 6
8
votes
9 answers

AC polarity detection

How can I detect AC 'reverse polarity' (single phase) (without the use of ground/earth) and drive a led when the polarity is reversed? It should at least detect 230 VAC but it would be cool/informative for future readers if the solution could…
zduk
  • 203
  • 1
  • 2
  • 8
1
2 3
…
15 16