Hot answers tagged

80

That's the Ukrsepro mark. It means the product has passed the certification of UkrSEPRO, the safety certification requirement symbol for trading in the Ukraine region. Scope of products covered by the above regulations include but not limited to the following: Information technology equipment Audio and video equipment Household and similar ...


48

20 amp glass cartridge type slow blow. It has a thermal mass that generates a delay before the solder melts at the left hand end. The spring pulls the mass away from the wire, making sure the two conductors separate and stay separated.


44

It's possible, and I've seen it done (the gear in question being a wideband amplifier for an EMC probe set), but for isolated low voltage only. The main drawback is the possibility of shorting the plug supplying power as swipes past the outer (ring) conductor. While it might be acceptable for a specialty power input with limited voltage and current, it ...


27

Yes there is, it is called an electronic load.


26

BobT has it right - my answer serves only to add information. This class of fuse is commonly known as a "3AG" or "3AB" fuse. The Buss number would be AGC-20 (fast blow) or ABC-20 (Slow Blow). Although they are still available with a clear glass housing, most modern versions now use an opaque ceramic housing for safety reasons (ceramic doesn't shatter or ...


23

If you want to convert the voltage to 5 volts, you should not use a resistance-voltage divider. That way you will indeed create 5 volts, but as soon as you apply a load the voltage will drop. Instead, you have two options in general to regulate voltage. The first option using a linear regulator, and the second option is using a switch-mode power supply. ...


22

In June 2004, the Economist, A financial / economy magazine should be read with a lot of caution when it comes to technical claims made therein – the people writing, interviewing, editing such a magazine aren't engineers! Just the same applies the other way around: I wouldn't trust IEEE Spectrum to be the best source for discussion of economy. in reference ...


19

The current marked on a motor should be the continuous, full-load operating current. The power marked on a motor should be the full-load mechanical power delivered by the shaft. A 3 Hp motor should deliver about 2240 watts. 2240/4600 is 0.487. That tells you that the motor's full-load power factor multiplied by its full load efficiency is 0.487. For a rough ...


19

What happens when the tip slides across the other contacts? TRS connectors are not ideal for power delivery because incorrect shorts can happen as the connector is mated.


18

It has been used for power in the past, but not so much any more, because it has proven to be a bad idea to use one connector for multiple purposes. Imagine the damage when accidentally plugging 12V supply into audio output or microphone input. That is also the reason why you don't want to use USB connectors for anything else than USB or HDMI connectors for ...


18

Resistors are all the same size no matter the resistance. It's convenient for the manufacturer to test how much power a certain-sized resistor can take before it burns up. And it's the same for all resistors of that size. Also the power rating is the same regardless of the resistor's exact resistance (within the tolerance). Cables with different current ...


15

History As other answers have observed, protecting both the power supply end and equipment end during connection and disconnection requires active electronics. The use of quarter-inch jacks originates in a time before silicon devices had been invented, so this simply was not possible. By the time electronics existed and could be put into something portable ...


14

Low energy density: for a given amount of energy, they take up more space than almost all battery technologies High leakage: this document has some nice curves. It looks like they've lost half the voltage after a week. Bad discharge curves: normal batteries might give you 80% of the power before they've dropped 20% voltage. Capacitors give out power evenly ...


13

Cables are rated for power too, but somewhat indirectly. They have a stated thermal limit as well as a maximum working voltage (insulation strength). Nevertheless it's usually more convenient to think of their current handling capability since their primary purpose is to do exactly that: move current. You would arrive at the cable's current rating from the ...


13

Study the circuit board and the components on it. Trace along the suspected positive and negative power tracks. Look for components that have identifiable positive and negative terminals. Electrolytic capacitors have their negative terminals clearly marked. If you can find data sheets for any integrated circuits on the PCB, see which are the power and ...


12

Google "laptop battery pinout". Typically you'll have: Plus and Minus power terminals (maybe several contacts each for higher current) Some form of communication like I2C Temperature sensing (for example a thermistor) Your typical laptop battery has several cells in series, so it requires balancing which is usually implemented in the battery management ...


12

If the signal is represented as a voltage \$v(t)\$ or a current \$i(t)\$ and it is connected to a (1 ohm) resistor, the power dissipated in the resistor is proportional to \$v^2(t)\$ or \$i^2(t)\$. Apart from that, defining power as a positive, increasing function of the signal amplitude has useful mathematical properties.


12

Cables are rated for power - it's just that it's not a useful way to think about it. The upper rating on cable size will be determined by how hot it gets before its insulation is damaged - and this will depend directly both on conductor size and insulation characteristics. Cables aren't intended to drop voltage, they are intended to carry current with an ...


11

That is just used as a comparator. The sine wave is either above or below the reference and that is the result of the comparison.


11

No, because the voltage rating is more about insulation between the conductors than it is about the characteristics of the load.


11

If you average the product of the current and voltage in this situation, you’d get zero. Think again... I think you need to look at the top left diagram (resistive load). Picture from this answer. See also these answers: - What's the most economical way to digitally measure 240V mains voltage, current and power factor? Average Power Versus Real Power ...


11

If you want to call it PoE, you need to stick to IEEE 802.3af-2003 or IEEE 802.3at-2009. These standards call for isolation. This answer could end here: no, you cannot build a PoE device without isolation. This is also assuming that the data lines are already isolated, so the only potentials without isolation is the power lines. You also will have a ...


11

I think that you have neglected the voltage drop across the diode which limits the current. My solution is : $$ \because V_{R_1}=V_0-V_f=5-2=3\,\text{V} $$ $$ \therefore I_f=I_{R_1}=V_{R_1}/R_1=3/1000=3\,\text{mA} $$ $$Power Loss =V_f\times I_f=2 \times0.003=6\,\text{mW} $$


11

It looks like the purpose of the circuit is to power-down at current zero-crossing (which would alleviate voltage spikes from interrupt current through an inductance, if there are any). When triggered, SCRs latch on and thereafter continue to conduct current. They only enter the blocking state if the trigger signal is removed and something else in the ...


11

Find a signal or shield ground on the module, and check with an ohmmeter to the connector. In all likelihood the power connector ‘sleeve’ is ground also, and will be zero ohms. The pin would be positive then. If it’s not, try the center pin to signal ground. If that is zero then the pin is GND and the sleeve is positive. You may now curse the designer ...


10

The clock undoubtedly operates charge pumps within the chip that provide bias voltages for various functional areas. Without proper bias, leakage currents are probably higher than the transistors are really designed to handle long-term.


10

The electrical connection at the bottom of the diagram also makes a good thermal connection. Very important for a power transistor. So, why can't you just reverse the Emitter and Collector in the diagram. You could, but it would be a lousy transistor. https://en.wikipedia.org/wiki/Bipolar_junction_transistor#Structure The collector surrounds the emitter ...


10

Shorting the input to ground can damage some regulators because the output capacitors and multifarious bypass capacitors which may be connected to the output discharge through the regulator. It's not necessarily easy to tell from the datasheet whether that is true. You could add a resistor between the switch and ground to reduce the chances of that happening....


10

Questions which call for speculation as to what someone meant are always deeply problematic. That said, there is a notable generation change in 2.4 GHz WiFi which fits your timeframe. 802.11b is a standard from 1999 802.11g is a standard from 2003 This may be significant, as 802.11g uses a higher throughput modulation scheme. As Texas Instruments argues in ...


10

I think the power efficiency trend of WiFi has more to do with the underlying CMOS technology and libraries than with choice of signal processing algorithms. Not only has the CMOS transistor feature been reduced into nanometer technology since then, but also newer low leakage devices are added to analog and digital circuits. As for digital circuits, new ...


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