# Tag Info

## Hot answers tagged electrical-engineering

128

If the receiver does not detect the sub-carrier for the "colour burst" signal which is transmitted during the horizontal blanking period the receiver switches on the "colour-killer" circuit so the set reverts to black and white mode. The colour-burst signal - 8 to 10 cycles of 3.85 MHz - is unlikely to be generated by random noise. Figure 1. The colorburst ...

108

This is another case of fancy new (SHINY!!!) technology being A Bad Idea(TM) . When you're driving, your eyes are focussed roughly at infinity, i.e. looking at objects more than 5 m away. When you look at a rear view mirror, you are still looking at distant objects. But when you look at a camera display, you're focussing on the image screen, which is ...

60

The problem is that the formula $P=I\ V$ is correct when dealing with DC circuits or with AC circuits where there is no lag between the current and the voltage. When dealing with realistic AC circuits, the power is given by $$P=I\ V\ \cos(\phi),$$ where $\phi$ is the phase difference between the current and the voltage. The unit kVA is a unit of what is ...

57

We still use mirrors because: A mirror is cheap, simple, passive technology that works. Pretty much the only failure mode is it breaking on impact. (Though I have had a center rearview mirror fall once because the adhesive that held it to the windshield failed.) Camera and screens are more expensive, more complex, active devices. There are many more ...

31

The industry is already going down that path for the exact reasons you mentioned. There is an article that provides information about that. In summary the main reasons why we don't have it yet are State laws require mirrors and would have to change first Conventional mirrors are basically fail safe, imagine the camera system turning off on the motor way. ...

30

The current limit specification for a wire is limited by the heat that current will produce, and how much heat the wire can dissipate before getting too hot. "Too hot" depends on the circumstances. You will see higher current ratings for the same type of wire in chassis wiring applications than the electrical code allows for home installations, for example....

28

As others stated before, induction loops are the primary - most reliable method: the coils (usually just several loops of wire) embedded in the road; fed given frequency from a generator, in presence of metal the frequency of the LC circuit changes and the sensor circuitry detects the change of frequency, producing a presence signal. In some cases these may ...

28

Both watts and volt-amps come from the same equation, $P=IV$, but the difference is how they're measured. To get volt-amps, you multiply root mean square (RMS) voltage ($V$) with RMS current ($I$) with no regard for the timing/phasing between them. This is what the wiring and pretty much all electrical/electronic components have to deal with. To get watts, ...

21

These types of motor configurations are used in the cellphone's vibrate/buzzer function. Here is a Youtube video demonstrating the vibrate function and two other references: How it works:Cell phone vibration motor? iPhone 5 / 5S Vibrator Motor Replacement Vibration Motors by Precision Microdrives Click on image for a larger version of the image. These are ...

21

Digital camera systems with LCD screens impose latency of at least a frame on the images. Fine for slow moving parking cameras, maybe a problem at speed. An object moving at 60mph shown through a 30fps camera with a latency of 1 frame is 1m away from where it appears to be. (CRT screens with analog TV cameras that have no digital in the signal path are ...

21

For a large and/or high speed fan, there are several mechanical disadvantages, for example The outer ring is highly stressed and therefore heavy. It may also need a heavy containment system to avoid collateral damage if it breaks. For example in a large turbofan jet engine, a mechanical failure caused by a crack near the hub of the fan usually only releases ...

19

Actually the turbine method is very efficient. The Turgo turbine is up to 90% efficient at extracting the energy from the water. Large-scale hydro plants using Francis Turbines can be as high as 95% efficient (see here). Electrical generators typically use high RPMs, so you need speed as well as torque to drive it round. Low RPM generators are possible too, ...

19

Pitch, roll and yaw are defined as the rotation around X, Y and Z axis. Below as a picture to illustrate the definition. In a previous project I used a ADXL345 Accelerometer from Analog Devices to calculate roll and pitch. Below are the equations used to calculated roll and pitch. I have made some of source code available for public use. accelerationX = (...

18

Several factors influence this: at high speed, there's a higher chance of the pantograph losing contact with the catenary wire: at higher speed, bumps in the wire cause a more violent excursion that can exceed the capability of the suspension of the pantograph. Low-speed trains can show arcing too. high-speed trains often use high voltage (15 or 25 kV), ...

15

There is heat that can be recaptured, but you won't get much of it away. As one of the commenters has mentioned, your absolute maximum is the Carnot efficiency. $$\eta_{Carnot}=1-\frac{T_c}{T_h}$$ This is an idealized condition, you'll never reach this efficiency. But to find our limit, let's figure it out anyway. $T_c$ will just be room temperature, it ...

15

Your equation is partly correct. You've calculated the energy per photon ($\hbar \nu$), but you've neglected the number of photons. That's why the units don't match (power is energy per unit time, while you've only got energy for each photon). The ideal power (energy per unit time) depends on the area of the solar panel, $A_p$, the number of photons ...

15

Not everything scales linearly. In particular, the cross-sectional area of supports required scales faster than height of a structure, all else held constant. This explains why ants have tiny thin legs compared to elephants. An ant linearly scaled up to elephant size would not be able to stand, or would snap its legs trying. The same thing happens to ...

14

I don't think they existed, and it has its reason. First: a solar panel can be characterized mainly by its efficiency spectrum: on which wavelength, which ratio of light energy can it convert to electric power. This needs to have its maximum around the visible light, becausd the Sun gives most of its energy in this wavelength interval. This is because our ...

14

There are good reasons why, although most of your links are from several years ago, very little has come of any of them. The economics and the engineering just aren't favourable. Part of the art of an engine is dumping the heat as quickly as possible; furthermore, heat is a low-quality form of energy, so once your energy is heat, you've already lost all your ...

13

In Ye olden days DC generators were brushed commutated devices. They had a one or more stator windings and an armature winding. Field wound DC generators as well as motors were commonly connected in one of three methods: Series, Shunt and Compound. Without getting into details, each had its own set of strengths and weaknesses. But you only have to remember ...

13

Distributed DC power is actually used in some new construction. It's driven less by the efficiency of the transformer than by other logistics. Here in California, at least, we have a law (known as Title 24) which requires some fairly sophisticated controls of lighting, as well as fairly low power consumption per square foot. The control requirements include ...

13

Trevor Archibald has given you a really good answer, but I see from your comments a diffferent answer might be useful, as you still think this could be viable with the right economics. It wouldn't be. The issue is engineering, not economics. It's a bad idea from the economic perspective, certainly; but changing prices won't make it a good idea. It would ...

13

There are two techniques commonly in use. The first is induction loops cut into the road surface. The metal in a vehicle body induces a current in the loop, as the vehicle passes over it. (public domain pic from wikipedia) The other is cameras / radar (either Doppler microwave for moving vehicles, or infra-red for static vehicles at the stop line), ...

13

There are two different ways for the water flow to transmit energy. One is the pressure difference between the water entering and leaving the turbine. The other the kinetic energy change of fast flowing water entering the turbine and slow flowing water leaving it. Your bucket idea seem to be like a http://en.wikipedia.org/wiki/Pelton_wheel which works by ...

13

Technology used in depth finder, in marine application is mostly like is the best to measure the water from the top. To measure water level from the bottom of tank one could use a piezo electric ceramic transducer combined with an Analog Front End (AFE) and a micro-controller to measure water level. The diagram below best explains the configuration. You ...

13

The device you are looking for is called a slip ring such as the one shown below. These devices use internal components which maintain contact as they spin (old ones used brushes) allowing them to turn by an unlimited amount in either direction.

13

What you show is a crude reflector. Yes, you can use reflectors around a antenna to get more power in a particular direction at the expense of other directions. This can be useful when the other antenna is in a known direction. However, there are several problems with this: It may violate the law. You don't give your location (remember that filling in ...

13

Yes, there are several different ways to manipulate magnetic fields. One way to shield an area from a magnetic field is to place a highly ferrous material like iron next to the source of the magnetic field. The iron will absorb the field in such a way that the magnetic field would be much smaller on the other side of the iron material. Notice how in this ...

13

The short and academically correct answer: a random noise signal is random. The lack of organization precludes that there is no separate color carrier present, and the set goes, as is already answered, into b/w mode. For split seconds there might be randomly something that looks like a color carrier might be present, then there might be a quick colorish ...

Only top voted, non community-wiki answers of a minimum length are eligible