23 votes

Extending USB cable makes it not work

The most prosaic reason why your cable doesn't work and is drawing too much current is that you connected he wrong pairs of pins and/or some of the the wires are shorted together. If that is not the ...
  • 12.6k
22 votes
Accepted

Extending USB cable makes it not work

Even aside from the fact that no outer sheath and no shielding makes me cringe, there are a couple of big issues with your custom cable: The data lines (pins 2 and 3) need to be a twisted pair. ...
11 votes

Does good electrical conductivity imply good thermal conductivity?

Beryllium oxide is a very good electrical insulator but at the same time the best non-metal (except diamond) thermal conductor. So to summarize. In general, good thermal conductivity is correlated ...
  • 1,046
8 votes

Why do electric cars claim "instant torque?"

ICEs (internal combustion engines) take some time to ramp up their output torque. Various mechanical systems have to react before more mixture is injected into cylinders, and that then makes more ...
  • 11.3k
8 votes
Accepted

How do electric companies supply electricity to homes in countries where energy is privatized?

Works similarly in the US (compared to UK responses). Natural monopolies are allowed to exist for utilities as it wouldn't make sense to have 3 or 4 different sewer lines running to everyone's home. ...
  • 2,347
7 votes

Does good electrical conductivity imply good thermal conductivity?

For metals, good electrical conductivity does indeed imply good thermal conductivity. This is known from the Wiedemann–Franz law, which gives the ratio between electronic contribution of thermal ...
  • 155
6 votes
Accepted

Why are coils used to generate magnetic fields

The current generated by a conductor moving through a magnetic field is related to the length of the conductor and the magnetic field strength. A coil is simply a convenient way to get a longer ...
  • 15.1k
6 votes

How do electric companies supply electricity to homes in countries where energy is privatized?

In the UK there are three different parts of the complete system: generation, transmission and distribution, and supply (sales) to customers. There are many companies that generate electricity, ...
  • 12.6k
5 votes
Accepted

Why do electric cars claim "instant torque?"

I think the instant torque claim mostly applies to "off the line" acceleration. That is from a standstill and electric motor has 100% of its available torque available at 0 rpm (mostly). The tradeoff ...
5 votes

Do kids under a certain age not hear the warning beeps that smoke detectors make when they are running out of battery power?

Unless they have hearing loss, young people tend to be able to hear a larger range of sound frequencies than older people, particularly higher frequencies: Some security companies recently began ...
  • 9,542
5 votes

Inverting motor polarities automatically to close and open a door

If I am not mistaken, you can use an H-Bridge for that. If you are using an arduino for example, there are a few motor drivers like L298N which do exactly that job (control the direction and speed of ...
  • 23.1k
4 votes
Accepted

What's the difference between aircon modes Auto, Sun, Snowflake?

The sun is heating mode. When the room temperature reaches the set temperature, the air conditioner stops operating until the temperature falls below the set temperature and the starts operating again....
  • 9,542
4 votes
Accepted

AC Motor On/OFF Control using SSR instead of contactor

Yes, but... There's not great data available on the Fokotek products, but in general switching HP sized motor loads with solid state relays is a fairly expensive proposition. Because the voltage and ...
  • 4,501
4 votes

What is the best practice for ensuring the best possible connection between a battery cable and a battery terminal

We really need more info on the batteries and type of connection. Will the connection be permanent? In that case soldering or welding are the best choices. If you're connecting to wire, you'll need ...
  • 1,743
4 votes
Accepted

How is electrical building code defined and applied to new constructions?

New homes are inspected by local authorities to comply with local building requlations. As Mike says, give them a call. The National Electrical Code (NEC) are standardized guidelines for electrical ...
4 votes

Extending USB cable makes it not work

For the USB signal, you have to make a 90 Ohm characteristic impedance twisted pair. The characteristic impedance depends on the insulator and on the outer/core diameter ratio of the wires. Search ...
4 votes
Accepted

Power systems unclear voltages

Note the problem specifies the load is "delta connected". There is no neutral connection to measure phase voltage ($V_{LN}$) against. Also note the supply frequency is 60 Hz. 208 V is a ...
3 votes
Accepted

Is it illegal to use the hydrodynamic energy contained within the city water supply to generate electricity?

Interesting problem. Let’s see, if we have a cylinder 12 inches in diameter and 8 feet high that would be (pi*(0.5f)^2*8f)*7.48 g/ft3=47 gallons per operation. ...
3 votes
Accepted

Quantifying Static Electricity Hazard with High Explosives

Static electricity is a major issue when handling or dealing with explosives. When blast holes are loaded with ANFO (ammonium nitrate fuel oil) as the main explosive, and a specific density of ANFO ...
  • 9,542
3 votes

Why do electric cars claim "instant torque?"

No, it's a characteristic that electric motors produce most, if not all, of their torque from zero rpm - which is why the electric cars are so good at getting off the line and how electric motors don'...
  • 14.6k
3 votes

Feedback on idea for a power station

For pretty fundamental physical reasons any power generator is only a way of converting one sort of energy to another ie converting the energy you have available to the sort of energy that you want. ...
  • 15.1k
3 votes

Electrical flowchart in Microsoft Visio : issues

I had to draw electrical and hydraulic schematics in Microsoft Visio at a past job. I'm glad that is behind me because that software is barely good enough for making flow charts. I would never ...
  • 7,559
3 votes

What is the name and purpose of this Instrumentation / Mechanical fitting

I'd call the blue part the transmitter housing. This usually contains electronics for sensor signal conversion, which converts the sensor (or probe) low level ...
  • 61
3 votes

How effective are pancake motors as generators and why

DC motors make fine generators. You can test them by connecting the shaft of the motor to the chuck of a variable-speed electric drill and connecting the motor wires to a load resistor; you then ...
3 votes
Accepted

What's the point of ESD-safe tweezers?

The tweezers that you are describing have what's known as a Static Dissipative coating. This coating is conductive, but it has a very high resistance. What this means is that they are able to ...
3 votes
Accepted

Why does audio equipment buzz/humm when a long signal cable is used and how do I eliminate it?

The reason for the humming noise is improper grounding. Audio signals are low voltage level AC signals (over simplified). An audio signal could be for example 1V, 1 KHz signal. When there is improper ...
3 votes

How is electrical building code defined and applied to new constructions?

Ever since 1975 use of at least one GFCI outlet and preferably more is mandatory in bathrooms or anywhere where there is the likelihood of moisture being near the outlet by NEC (National Electric Code)...
  • 21.4k
3 votes

Extending USB cable makes it not work

The device is likely not getting the power it needs. Use a thicker wire to ensure the resistance is the same as the original. Don't make an induction coil with your cable. It also helps to use ...
  • 1,084
3 votes

How to manage real-world too-long data cables?

Sorry, but the answer is "don't." When you use cables greater than (or even close to) the max rated length for a given comms protocol, you are asking for glitches and failures to occur. ...

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