12
votes
Accepted
What is it about the cabin electrical supply on cruise ships that makes surge protectors dangerous?
From USCG Surge Protective Devices Onboard Vessels
A marine casualty investigation of two separate stateroom fires onboard a U.S. Flag Container ship revealed that the sources of the fires were ...
- 2,467
9
votes
Accepted
What causes the sound coming from electrical vehicles?
Correct, coil noise is generated in the windings of the motor because of Pulse Width Modulation (PWM) driving current. Different frequencies of modulation cause corresponding sound frequencies (may ...
- 7,904
9
votes
Accepted
What device is this, and how does it work?
Something like this?
http://www.browninnovations.com/sound-dome/single-localizer-sound-dome
As others have said, it is a speaker with a parabolic reflector to direct the sound down at the listener. ...
- 766
8
votes
What device is this, and how does it work?
With a description as vague as that, it was probably a parabolic reflector with a speaker at its focus. Pointed straight down, the "beam" of acoustic energy would be reflected from the floor right ...
- 6,874
6
votes
Accepted
Why do kWh (smart) meters have a maximum operating altitude?
Electronic components are rated for altitude because:
Air density affects convective cooling, both forced and natural, meaning the cooling is reduced at altitude.
Air density affects air's dielectric ...
- 6,534
5
votes
Accepted
What is micro-electromechanical systems (MEMS)?
One way to think of MEMS is regular mechanical systems, but at a very small scale. Often these tiny systems are fabricated using technology developed for making silicon electronic chips, like ...
- 11.4k
4
votes
How can I find the emission power of a WiFi mobile phone antenna?
Typically, the max is 100mW (20dBm). You can refer to an example wifi chip datasheet (This one is used in many mobile phones with Snapdragon processor) -
https://developer.qualcomm.com/download/sd410/...
4
votes
Accepted
Why is it bad to run power through BNC (RG58) cables?
Because it is not a power cable (Q1) using power connectors (Q2).
BNC cable has a solid conductor and a ground braid to electrically shield and mechanically protect the conductor.
Electrical reason: ...
- 2,467
3
votes
How can I find the emission power of a WiFi mobile phone antenna?
There is a list of some widely used devices and their transmit power (and many other properties) in an easily digestible table: https://clients.mikealbano.com/
The most smartphones seem to be just ...
- 131
3
votes
Why are bird flight diverters shaped like a spiral?
Originally the spiral shaped devices were fitted to the earth wires on top of pylons as vibration dampers (the very top single wire on pylons is the earth wire). It was however noted that they also ...
- 66
3
votes
What is micro-electromechanical systems (MEMS)?
MEMS is a semiconductor based process that can create miniature structures in silicon. When these structures (sensors) are subjected to mechanical stresses (pressure, acceleration, yaw etc) they are ...
- 7,125
3
votes
Generating practical power without an iron core, but with high RPM
the iron structure(s) inside a generator serve the purpose of minimizing flux leakage, which maximizes the utilization of the magnetic field in generating electricity. One of the ways in which they ...
- 14.3k
3
votes
What is the function of jumper pins on a 4 channel relay?
Each channel can be set to be triggered high or low.
See User Manual
- 2,467
3
votes
Preventing a DC motor from stalling
Considering that this is a class project, depending on what you use to control the DC motor, you might be able to use current limiting. The technique is called current sensing.
When a DC motor is ...
- 24.3k
3
votes
How to match a circuit relay online
For this specific relay, a quick search returns many results. One of them is from Mouser, an electronics component source.
There is a link on the web site for the data sheet for the relay. Some of the ...
- 6,940
3
votes
Accepted
Why design chargers with USB port on a side rather than top
I think that the power adapter was probably first designed for the North American market.
For that market, the design is not flawed.
- 320
3
votes
Why do kWh (smart) meters have a maximum operating altitude?
Expanding item 2 in Tiger Guy's good answer I'd say it's definitely about dielectric strength.
Electronic devices manufacturing standards (e.g. IEC62368-1) define creepage and clearance distances ...
- 295
2
votes
Accepted
Identifying affordable alternatives for low-frequency high-current DC-DC solid state relays
SSR or Solid State Relay is what you are after. You should be able to trigger this one right off the 3 volt rpi gpio. FOTEK SSR-40DA. Here is a DC one CPC1709J. Use a voltage divider or zener diode so ...
- 7,904
2
votes
Accepted
Some questions about liquid nitrogen cooling
Regarding questions 2 and 3, I think you need to look deeper in the chemistry, reactivity, and heat transfer characteristics of Nitrogen.
1) It is not a noble gas. It is reactive, and you benefit ...
- 196
2
votes
Accepted
PED or DSP for mechatronic student
DSP is relevant to any engineering field that involves gathering data and/or controlling something. That includes almost all robotics applications.
It's not quite clear just from the title what "...
- 12.5k
2
votes
Is current suppose to pass through a capacitors dielectric? What happens if it does?
Here is a good link on Capacitors. Capacitor is a energy storage device. Capacitor can act like a battery. Stored energy is discharged to a device like an LED. Take a look at this capacitor battery ...
- 772
2
votes
Control power to a tungsten filament?
We have a test rig that works something like this, to heat up small objects (typically cubes of material with sides a few mm long) to about 1000C fairly quickly.
The heat source is a "tube" of ...
- 12.5k
2
votes
Power consumption of mining rig?
Since I lack the reputation to write comments:
The electricity cost of mining is way higher than the earnings. Small scale mining is not profitable anymore for a long time already, mining farms have ...
- 1,863
2
votes
why do 15kV 60mA transformers have to be so big?
Voltage and Current multiply to give power. 15kV times 60mA is the same as 60Volt times 15 Amps (=900 Watts) You would not expect that to be a tiny thing, would you? And that power is without ...
- 186
2
votes
Accepted
Maximum amps from a switching voltage regulator
That is an oversimplification.
From the data sheet http://www.ti.com/lit/ds/symlink/lm2596.pdf there are two relevant features, internal over-temperature protection and a maximum current limiter (...
- 12.5k
2
votes
What is this gigantic high-tech cylinder in the corner of a middle-class Chinese family's living/dining room in Shanghai?
It's a guess, but an informed one, based on the 20°C / 68°F indicator on the digital display. One might believe that this is the desired temperature or the current temperature. From there, it's an ...
- 6,940
2
votes
Why do most BMS systems for li-ions and li-pos stop discharging at 2.5V? Are there better systems or is this the standard
This may be for a couple of reasons.
The battery voltage will sag during high current draw, if the cutoff is too high it might trip even though the battery has plenty of capacity remaining.
It may be ...
- 1,901
2
votes
Effects of Solar Shield on Electronics Enclosure
If you are worried about the solar radiation (which is understandable), a much more affordable solution might be to put the whole thing in a shade if its possible, with enough clearance from the ...
- 24.3k
2
votes
Accepted
AC Harmonics on a system appearing as DC
In general, a load which is "symmetrical" with regard to the positive and negative half-cycles of the mains will only generate odd harmonics. If the load is not symmetrical and the current ...
- 10.3k
Only top scored, non community-wiki answers of a minimum length are eligible