Questions tagged [power]

Where power is a primary concern for the design under discussion. Use the "low-power" tag when that applies.

Filter by
Sorted by
Tagged with
-1
votes
2answers
215 views

Switching Between Two Power Supplies Without Reverse Current

I'm new to electronics, so I'm bound to have gotten something wrong. I'm designing a basic sensor and want it to be powered by USB by default, but use a lithium polymer battery when not connected via ...
10
votes
4answers
752 views

Proper ways to disconnect ICs during low power states to avoid parasitic/backfeed supply

I’m working on a low-power battery-based AVR-based project that integrates a few different devices including a neopixel strip and an Adafruit pixie. When the overall device is quiescent, I’d like it ...
9
votes
4answers
2k views

IGBT ratings, I don't understand how this is possible

I found the IXGX400N30A3 at Digikey. The datasheet says the device is rated for 400A @ 25C, 1200A @ 25C for 1ms, with a voltage rating of 300V and PD of 1000W. Really? This TO-264 package can ...
9
votes
4answers
4k views

Limiting the short circuit current of a power supply

I'm using a repurposed ATX power supply for my hobby projects since it's got 3.3/±5/±12 outputs, all of which are really convenient. But one thing I didn't really think about until I slipped my probes ...
6
votes
2answers
11k views

Power line communication principles

What are the principles of implementing Ethernet over power lines ? Is it reasonable/possible to create an Arduino shield which will provide both power & network ? (properly isolate the "dangerous ...
6
votes
2answers
2k views

How to go about sensing AC power in existing wiring

Is there a practical way to sense 60Hz AC power in a pair of wires? Measuring the exact power or even current isn't necessary; it would be sufficient to know whether the load is pulling more than, say ...
6
votes
2answers
3k views

How to measure power consumed by mains device

I would like to measure the power consumed by a mains device. I have heard that it's not as trivial as simply measuring the average current, as the device may be resistive, capacitive or inductive, ...
5
votes
6answers
1k views

High Voltage differential Measurement

Suppose I want to measure individual cell voltage of a 12-serial-cell battery pack, what would be my most economical options? Single cell voltage is 3V-4.2V but the stack can be between 2-12 cells ...
4
votes
2answers
528 views

How to power a button's LED within a guitar?

I'm working on a guitar, and the plan is to use three latching push buttons so that each pickup can be turned on and off individually. I'm fairly confident that the following diagram should work for ...
4
votes
2answers
1k views

High current mechanical relays

I'm looking for a mechanical relay that can run 500 amps when closed. There are solid state solutions for switching such currents (SSRs, IGBTs, etc), and we do use them, but for a low speed H-bridge ...
3
votes
3answers
137 views

Why is power factor such a meaningful quantity?

In my current electrical engineering course the concept of power factor has been a large topic, defined as the ratio of real power to apparent power. It is a measure of resistive power consumption in ...
3
votes
3answers
867 views

How to calculate power from this diagram?

I need to calculate the apparent power, active power and reactive power and I only got this diagram ( in german ): So the equation for active power is $$P = \int_0^T u(t)i(t) \, \mathrm{d} x$$ ...
2
votes
2answers
15k views

Understanding Royer oscillator (for wireless power transfer), (specially mosfet gate driver circuit)

I need to understand how exactly this circuit works, there is not much references and books on those circuits, they're used as "power" oscillator for DC AC conversion for wireless. i finally found ...
2
votes
3answers
536 views

Isolation provided by transformers

I have a few questions about transformers and isolation. I will describe my understanding (maybe wrong) and questions about them. Transformers provide safe isolation by disconnecting two circuits ...
1
vote
3answers
12k views

Max Voltage for Speaker of Given Power Rating

I have been looking into the design of loudspeaker drivers and would like to know how to determine the maximum voltage which can be delivered to a given speaker. From Ohm's law we know that P = V^2 / ...
0
votes
1answer
826 views

Hacking DSLR battery to power camera from power supply [closed]

I would like to power my DSLR for long captures with a power supply. I know the voltage and inner structure of the official batteries. The battery has 2x 3,7V cells inside with a circuit. People ...
0
votes
2answers
1k views

Transformer VA Ratings, Power factor, and Pulsed current

What exactly goes into a transformer's VA rating? At a fundamental level it seems that there has to be a limit to what the VA rating can represent. For example if I draw 2 Amps-RMS from the secondary ...
-2
votes
3answers
2k views

Calculating the power of a simple amplifier

I found this circuit on internet. It says it's a 1w amplifier. There is no explanation about how that is calculated. How could the power of this circuit calcuted? (input is a radio) And is there any ...
15
votes
1answer
9k views

Why do ceramic insulators have a stacked disc structure?

I've seen these stacked-disc structures on high voltage power lines everywhere. I could not find any information regarding this particular shape, though. From what I've noticed, high voltage ceramic ...
10
votes
5answers
13k views

Understanding electrical consumption

I have problems understanding the difference between electrical power and consumption. Can you help me understand what electrical energy consumption is? Let's say that I have a bulb, on which is ...
10
votes
3answers
934 views

What is the difference in this specific breadboard wiring?

As an absolute layperson in electronics I just found out that an LED only lights up when connected like in figure 1 but not when connected like in figure 2. And I just don't get why? I know an LED is ...
9
votes
9answers
1k views

Neophyte question about AC vs. DC (especially for powering a home)

Here in the United States the electricity grid is AC. I have heard that AC allows transmission of power at greater distances with less loss. However, with the advent of solar panels, it would seem ...
6
votes
4answers
10k views

Microcontroller with lots of PWM outputs

I'm looking at some microcontrollers for power converters control (dsPIC33F and some ARM Cortex M3/M4 like the STM32F372CBT6 for instance) and I'm a bit worried by the limited number of PWM outputs (...
5
votes
2answers
1k views

Best options for limiting input ringing with ceramic capacitors

Ceramic capacitors have this unfortunate property which can cause spikes in voltage when live batteries are connected to boards (hot-plugging), due to the inductance of the wires to the batteries and ...
4
votes
2answers
3k views

Passive POE: Need 5V @ 2A at the destination

Having a bit of trouble finding the right information on google, and I'm worried I might fry some cables so I thought it best to ask some far more knowledgable than myself. I want to connect 2 or ...
4
votes
3answers
3k views

Help with a simple comparator circuit

I'm trying to build a simple temperature controller by using a thermistor and a potentiometer attached to a Schmidt trigger to control a relay. I realize that I have some serious design flaws in ...
3
votes
2answers
1k views

Raspberry Pi and USB modem - can I connect it like this?

As some of you know - Raspberry Pi model B has only 100mA available on USB ports. I want to connect USB modem (that takes > 500mA sometimes) to my Raspberry without powered USB hub. I have: ...
3
votes
1answer
448 views

Measuring precisely the efficiency of a power converter

I am trying to measure the efficiency of a DC/DC boost-converter in several operating points as precisely as possible. Right now I am measuring my input-voltage and output-voltage with a multimeter, ...
3
votes
1answer
502 views

Powering 16 meter LED strip

I have 16 meters of WS2812B LED Strips similar to the ones on adafruit. The strips have 60 LED/s per meter and run on 5 volts. They come in 4 meter reels. I know how i want to control them but i am ...
3
votes
1answer
2k views

How does one measure the power factor?

How does one measure the power factor? $$\text{power factor}\equiv\frac{\text{power}}{|V||I|}=\frac{R}{\sqrt{R^2+(1/\omega^2C^2)}}$$ for an RC circuit driven with \$V(t)=V_0\cos{(\omega t)}\$.
2
votes
5answers
328 views

I have a problem with power equations

As we know the power equations are P=VI, P=V2/R or P=I2*R. My question is: how I can increase the power by increasing and decreasing the resistance? In the formula P=V2/R, if I want to increase the ...
2
votes
6answers
5k views

Why is a laptop power supply output voltage different from its battery?

I hope you will not mind answering. This question has long been on my mind. Normally, the adapter output voltage is higher than that of the battery. In my laptop's case, the output voltage of the ...
2
votes
1answer
1k views

How do I calculate battery life for my devices?

I want to power coupe devices via car battery, but before I do that I want to figure out how long battery will last. Most of the devices work from 5V so I am using 12Vto5V converter (link to item on ...
2
votes
2answers
575 views

Can this temperature-controlled fan circuit be modified for different input voltage?

I want to know if this same circuit can be used for 220 or 230 volt input, and if there are any components that need to be modified. C3 has 600V capacity and C1 and C2 have 250 volt. Link to original ...
2
votes
3answers
645 views

Electrical System Harmonics

I'm a mechanical engineer so I don't know much about electric circuits and power generation to begin with. Can somebody explain what a harmonic is in the power grid and what is the reason why it is ...
2
votes
1answer
943 views

Can I use a power amplifier for power stage of a pure sine wave inverter?

As the title reads, I wish to use a power amplifier (say OPA541) in the power stage of a 50W pure sine wave inverter? How to find the efficiency of this approach? Since the amplifier itself will be ...
2
votes
2answers
197 views

Ideal LC circuit decays over time in LTspice

I was trying to simulate a transformer without a load, and setting an initial condition to observe how the energy will flow from the primary to the secondary circuit. I realized that the energy will ...
2
votes
3answers
3k views

Can the power source for a USB device be different from the data source?

I was wondering if the data source (USB Host) for a USB device has to also deliver the power 5V circuit e.g. data and power need to have a common ground. Or can I connect the data lines to the data ...
1
vote
2answers
1k views

Proper Decoupling

I have this circuit connected to an Arduino DUE. It is an audio application and it works, but I have a ton of noise in my project. I initially thought it was quantization noise because the ADCs are ...
1
vote
1answer
921 views

Buzzing power supply

I have a power supply that buzzes when nothing is connected and is silent when there is a power drain. What could it be? It's a PC power supply that I used to power an LCD through its 12 V line.
0
votes
1answer
148 views

Amplifier Power Requirements

This link states that when determining the power needed by an amplifier, you use the following formula: I understand that the second term is due to the quiescent draw of the amp, but how is the first ...
0
votes
1answer
4k views

Synchronising Power & Synchronising Coefficient

I am really confused with the concept of synchronising power and synchronising coefficient. I was taught 2 simple formulae in class. P = 3VEsin(del)/X Sp = dP/d(del) = 3VEcos(del)/X Now, I am ...
0
votes
1answer
112 views

What's the function of the three input resistors in the below circuit?

I want to know the function of the three 1Mohm resistor between the HVDC+ and HDVC-, they are R4 R14 and R17 in the below circuit, thanks for your attention and time!
0
votes
3answers
518 views

Why do electrical systems have neutral, live and ground when electronic systems have only VCC and ground?

Wouldn't it be simpler if electrical systems take away the neutral and just have live and ground similar to electronic systems?
0
votes
2answers
2k views

How do I tell which wires are Red/Positive and Black/Negative on these fans?

thank you for taking the time to answer this question : Here are the fans in question... I only ask because I burnt both fans trying to find the right wires, so I guess I put the wrong wires on for ...
0
votes
2answers
3k views

Can Average Power of a 3-Phase AC motor be calculated from Mean Current & Voltage RMS from each winding?

If this is possible could a formula be provided. + Explaination. Thanks very much in advance. FYI I am completely new to this site so please be kind. Could I ask that any criticism be constructive. ...
0
votes
3answers
3k views

Burned out potentiometer

DISCLAIMER: I am just tinkering with electrical engineering and can barely do the basics yet. Background I have done a little work on a breadboard connected to my Raspberry Pi, but today I wanted to ...
0
votes
2answers
744 views

Switch between two power supplies

[![enter image description here][1]][1]I am trying to build a simple circuit to power a load with two different power supplies (5 V and 0.7 V). When one is active the other one is not and it's ...
0
votes
2answers
591 views

Capacitor size across power source selector relay

Two sources of power: 12V switched power supply (primary) 12V deep cycle lead acid battery (secondary) Note: In practice the switched power supply voltage will be adjusted to match the actual ...
0
votes
1answer
75 views

Should I add Capacitance on Switched High Side

Following from this question, which remains open... if I've got a microcontroller switching the high-side power to a sub-system, using a circuit like this: ... should I add bulk and/or decoupling ...

1 2
3
4 5
9